Chapter 1. Welcome to EJB
Table of Contents
Chapter 1. Welcome to EJB.......................................................................... 1
Section 1.1. OBJECTIVES............................................................................................................................................................... 2
Section 1.2. What is EJB all about?................................................................................................................................................. 3
Section 1.3. What does EJB really give me?................................................................................................................................... 4
Section 1.4. No more vendor lock-in!............................................................................................................................................. 5
Section 1.5. There are no Dumb Questions.................................................................................................................................... 6
Section 1.6. How does it all work?................................................................................................................................................... 7
Section 1.7. Behind the scenes........................................................................................................................................................ 8
Section 1.8. Sharpen your pencil................................................................................................................................................... 10
Section 1.9. Beans come in three flavors....................................................................................................................................... 11
Section 1.10. Session beans can be stateless or stateful................................................................................................................ 12
Section 1.11. There are no Dumb Question................................................................................................................................... 12
Section 1.12. Sharpen your pencil.................................................................................................................................................. 13
Section 1.13. Overheard at! THE TIKIBEAN LOUNGE................................................................................................................ 14
Section 1.14. Example: The Advice Guy bean................................................................................................................................ 15
Section 1.15. Five things you do to build a bean:.......................................................................................................................... 16
Section 1.16. EJB Roles and Responsibilities............................................................................................................................... 26
Section 1.17. Tutorial:.................................................................................................................................................................... 28
Section 1.18. Organize your project directory............................................................................................................................... 29
Section 1.19. Compile the two interfaces and the bean class....................................................................................................... 30
Section 1.20. Start the server......................................................................................................................................................... 31
Section 1.21. You'll see something like this................................................................................................................................... 31
Section 1.22. Start deploytool....................................................................................................................................................... 32
Section 1.23. you'll see something like this................................................................................................................................... 32
Section 1.24. Make a new Application.......................................................................................................................................... 33
Section 1.25. There are no Dumb Questions................................................................................................................................ 33
Section 1.26. Name and save the new application........................................................................................................................ 34
Section 1.27. What you'll see af ter you create and name the application................................................................................... 35
Section 1.28. Now let's make the new enterprise bean (the ejb-jar and the DD)........................................................................ 36
Section 1.29. Now we're in the really cool New Enterprise Bean Wizard.................................................................................... 37
Section 1.30. Create the new ejb-jar............................................................................................................................................. 38
Section 1.31. Add the three class files (including their package directory) to the JAR............................................................... 39
Section 1.32. Confirm that you added ONLY the package directory and the class files.............................................................. 40
Section 1.33. Make it a Stateless Session bean.............................................................................................................................. 41
Section 1.34. Tell it which of the three class files in the JAR is the actual BEAN class............................................................... 42
Section 1.35. Tell it which is the Home interface, and which is the Component interface......................................................... 43
Section 1.36. Verify everything on this screen!............................................................................................................................ 44
Section 1.37. You're done, click Finish.......................................................................................................................................... 45
Section 1.38. Meanwhile back on the main deploytool screen.................................................................................................... 46
Section 1.39. Run your bean through the deploytool verifier...................................................................................................... 47
Section 1.40. Close your eyes and click OK.................................................................................................................................. 48
Section 1.41. Whew! No failed tests.............................................................................................................................................. 49
Section 1.42. Time to Deploy........................................................................................................................................................ 50
Section 1.43. Make it Return a Client Jar...................................................................................................................................... 51
Section 1.44. Give it a name, so clients can look it up.................................................................................................................. 52
Section 1.45. Watch the progress bars go up, then celebrate....................................................................................................... 53
Section 1.46. Now you'll see the AdviceApp inside the server..................................................................................................... 54
Section 1.47. Now all we need is a client....................................................................................................................................... 55
Section 1.48. Organizing your project directory for the client..................................................................................................... 56
Section 1.49. The Client Code (AdviceClient.java)....................................................................................................................... 57
Section 1.50. Run the client!......................................................................................................................................................... 58
Section 1.51. COFFEE CRAM........................................................................................................................................................ 59
Section 1.52. COFFEE CRAM....................................................................................................................................................... 60
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
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Page 1
Intro to EJB
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
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Page 3
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 4
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 5
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 6
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 7
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SERVER JUMPS IN AND STARTS ASKING QUESTIONS LIKE
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 8
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
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Return to Table of Contents
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 11
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 12
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FOR SAVING THAT STATE LIKE USING
THE CLIENT TO STORE STATE OR USING
A SERVLET TO STORE STATE OR USING A
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ARE MORE OF A PERFORMANCE HIT
THAN THE LESS SCALABLE NATURE OF
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 13
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 14
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 15
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UNDERSTAND EVERYTHING HERE $ONT WORRY
ABOUT IT NOW WELL lGURE IT ALL OUT IN LATER
CHAPTERS 4HIS IS JUST TO GIVE YOU A FEELING
FOR WHAT ITS LIKE TO GET A BEAN UP AND
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 16
Return to Table of Contents
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 17
Return to Table of Contents
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IMPLEMENTATION OF YOUR BUSINESS
METHODS DElNED IN THE COMPONENT
INTERFACE )N OTHER WORDS YOU WRITE YOUR
BUSINESS LOGIC IN THE BEAN CLASS
4HERE ARE THREE BEAN TYPES TO CHOOSE
FROM 3ESSION %NTITY AND -ESSAGE DRIVEN
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CHAPTERS OF THE BOOK "EFORE MAKING
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TYPE YOU NEED BECAUSE YOUR BEAN CLASS
MUST IMPLEMENT ONE OF THREE INTERFACES
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7EVE CHOSEN A 3ESSION BEAN HERE
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 18
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 19
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 20
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SOME DEVELOPERS DO 3OMETIMES THE CHOICE OF WHICH TO DEVELOP lRST
DEPENDS ON THE DEVELOPMENT TOOLS YOURE USING TO BUILD YOUR BEANS
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TO MATCH !ND SOME TOOLS DO JUST THE OPPOSITE LOOKING AT THE
INTERFACES AND BUILDING A hYOUR CODE GOES HEREv BEAN CLASS WITH ALL
OF THE METHODS FROM THE INTERFACE &OR LEARNING %*" WE LIKE TO START
WITH THE BEAN FOCUSING ON THE BUSINESS LOGIC BEFORE lGURING OUT THE
INTERFACES ,ATER IN THE BOOK WELL DO IT THE OTHER WAY AROUND
!S FOR THE BEAN NOT IMPLEMENTING THE COMPONENT INTERFACE YOU COULD
DO IT THAT WAY BUT THIS TIME WE STRONGLY URGE YOU NOT TO /N THE NEXT
PAGE WELL LOOK AT THIS IN MORE DETAIL
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 21
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3O WHY DOESNT THE BEAN
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NEED TO IMPLEMENT IN YOUR CODE ,IKE
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!74 7HY NOT DO SOMETHING LIKE THAT
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BEAN THAT IMPLEMENTS THE METHODS
A:
A:
,EGALLY THE BEAN CLASS CAN
IMPLEMENT THE COMPONENT INTERFACE
BUT THE SPEC DOESNT RECOMMEND IT
2EMEMBER ALTHOUGH TO THE CLIENT IT
LOOKS AS THOUGH THE !DVICE"EAN IS THE
OBJECT THE CLIENTS INVOKING METHODS
ON THE OBJECT THAT IMPLEMENTSˆIN
THE TRUE *AVA SENSEˆTHE COMPONENT
INTERFACE THE CLIENT REALLY INVOKES
METHODS ON SOMETHING CALLED AN
%*"/BJECT THATS IMPLEMENTED BY THE
SERVER AT DEPLOY TIME 4HE CLIENT NEVER
INTERACTS DIRECTLY WITH THE BEAN .EVER
EVER EVER ,ATER IN THE BOOK YOULL SEE
THAT IF THE BEAN DOES IMPLEMENT THE
COMPONENT INTERFACE YOU COULD SNEAK
THINGS PAST THE COMPILER THAT WOULD
EXPLODE AT RUNTIME 3O WE STRONGLY
URGE YOU NOT TO HAVE YOUR BEAN
IMPLEMENT THE COMPONENT INTERFACE
"UT THERES ANOTHER ISSUE AS WELLˆTHE
COMPONENT INTERFACE EXTENDS ANOTHER
INTERFACE )N OUR EXAMPLE !DVICE
EXTENDS %*"/BJECT AND %*"/BJECT
IS NOT A MARKER INTERFACE )T HAS
METHODS 4HIS MEANS THAT ANY CLASS
IMPLEMENTING !DVICE MUST ALSO
IMPLEMENT THE METHODS OF %*"/BJECT
9ES YOU COULD DO THAT AND IT
WOULD BE LEGAL "UT IT STILL MEANS YOUR
BEAN IS CAPABLE OF HAVING METHODS
INVOKED THAT THE BEAN SHOULD
NEVER KNOW ABOUT 4HE METHODS OF
%*"/BJECT ARE METHODS FOR THE CLIENT
TO CALL ON THE BEAN BUT ./4 FOR THE
BEAN TO ACTUALLY IMPLEMENT 3O ITS NOT
THE BEST // PRACTICE
!ND THERES STILL ANOTHER REASON WHY
ITS NOT GOOD PRACTICE TO HAVE THE
BEAN IMPLEMENT THE COMPONENT
INTERFACEˆIF THE INTERFACE IS REMOTE
AND %*"/BJECT IS SINCE IT EXTENDS THE
JAVARMI2EMOTE INTERFACE THAT WOULD
MAKE THE BEAN CLASS A 2EMOTE CLASS
AND THAT MUST NEVER BE 4HE BEAN IS
PROTECTED BY THE SERVER AND MUST
NEVER BE ACCESSED IN ANY OTHER WAY
BY ANYTHING BUT THE SERVER )TS THE
SERVER THAT MAKES THE %*"/BJECT BY
IMPLEMENTING THE !DVICE INTERFACE
WHICH )3 REMOTE AND WHICH INTERCEPTS
ALL BUSINESS METHOD CALLS TO THE BEAN
Q:
"UT IF YOU DONT HAVE THE
BEAN IMPLEMENT THE INTERFACE IN
OTHER WORDS IF !DVICE"EAN DOESNT
IMPLEMENT !DVICE DOESNT THIS MEAN
THAT THE COMPILER WONT CATCH YOU IF
THE BEAN BLOWS IT AND DOESNT MATCH
THE METHODS OF THE INTERFACE
A:
9ES THATS EXACTLY WHAT IT
MEANS !ND YES THAT MAKES MOST
*AVA DEVELOPERS A LITTLE QUEASY JUST
THINKING ABOUT IT !FTER ALL THATS ONE
OF THE BENEFITS OF INTERFACES IN *AVAˆ
THAT THE COMPILER GUARANTEES THAT
YOU HAVE ALL OF THE INTERFACE METHODS
PROPERLY IMPLEMENTED
"UT DONT PANIC )N OUR DEVELOPMENT
IN THIS BOOK WE DO HAVE TO BE CAREFUL
SINCE THE COMPILER ISNT MAKING SURE
THAT WEVE IMPLEMENTED THE BUSINESS
METHODS FROM THE COMPONENT
INTERFACE )N THE REAL WORLD HOWEVER
YOULL ALMOST CERTAINLY BE USING AN
%*" READY DEVELOPMENT ENVIRONMENT
THAT WILL MAKE SURE YOU PROVIDE THE
METHODS EITHER BY PUTTING A hYOUR
CODE GOES HEREv VERSION OF THE METHOD
IN YOUR BEAN CLASS OR BY DOING THE
REVERSEˆFINDING THE BUSINESS METHOD
IN THE BEAN CLASS AND PUTTING IT INTO
THE COMPONENT INTERFACE !T THE VERY
LEAST MOST SERVERS WILL CHECK BEFORE
OR AT THE TIME YOU DEPLOY THE BEAN
THAT YOUR COMPONENT INTERFACE AND
BEAN CLASS HAVE MATCHING METHODS
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HAVE A TECHNIQUE FOR GETTING AROUND IT
THAT WELL LOOK AT A LITTLE LATER #HANCES
ARE YOU WONT NEED TO USE IT
3O YOUR BEAN WOULD END UP
IMPLEMENTING A BUNCH OF METHODS IT
SHOULD NEVER HAVE LIKE GET(ANDLE
GET%*"(OME \RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 22
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 23
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4HE DEPLOYMENT DESCRIPTOR $$ DESCRIBES THE STRUCTURE
OF YOUR BEAN INCLUDING HOW THE THREE lLES COMPONENT
INTERFACE HOME INTERFACE AND BEAN CLASS ARE RELATED TO ONE
ANOTHER 4HE SERVER WONT LOOK AT YOUR NAMING CONVENTION
AND lGURE OUT WHICH IS THE HOME WHICH IS THE BEAN ETC 9OU
HAVE TO TELL THE SERVER THROUGH THE $$ WHICH CLASS IS WHICH
AND HOW THEYRE CONNECTED "UT THE $$ DOES A LOT MORE THAN
THAT !ND FOR SOME BEANS THE $$ CAN BE SEVERAL PAGES LONG
&OR THIS SIMPLE BEAN THE $$ IS SHORT 2EMEMBER YOU DONT
NEED TO MEMORIZE THE SYNTAX OF THE 8-, IN THE $$ ,ATER
IN THE BOOK IN SEVERAL DIFFERENT CHAPTERS WELL GO OVER THE
ASPECTS OF THE $$ THAT YOU DO NEED TO KNOW
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 24
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!S A BEAN DEVELOPER OFlCIALLY CALLED A "EAN 0ROVIDER YOULL ALWAYS PUT YOUR BEANS IN
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CLASSES AND INTERFACES ALONG WITH THE DEPLOYMENT DESCRIPTOR 9OU DONT HAVE TO DO THIS BY HAND SINCE WELL USE THE 2) 2ATHER THAN WRITING THE 8-, $$
AND USING THE MDU TOOL TO PACKAGE IT WELL USE THE 2) GHSOR\WRRO WIZARD TO MAKE IT
EASIER AND LESS ERROR PRONE )N OTHER WORDS WERE GOING TO COMBINE STEPS AND INTO
ONE &OR NOW YOU NEED TO KNOW THAT A BEAN ISNT A BEAN UNTIL YOU MAKE A *!2 lLE WITH
THE COMPILED CLASS AND INTERFACES AND THE $$
t descriptor
The deploymenmed Òejb-jar.xmlÓ
MUST be nabe in a directory
and MUST TA-INFÓ
named ÒME
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lude all three of
the bean .class Þles (thinc
plus the bean implementeatitwo interfaces
on class) and
the deployment descr
or. Name the
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like; thereÕs no
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 25
LQWURWR(-%
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3OONER OR LATER YOUR BEANS HAVE TO DO SOMETHING 4HEY HAVE TO BE ASSEMBLED
INTO AN APPLICATION AND DEPLOYED INTO A SERVER WAITING FOR CLIENTS TO CALL
4HIS IS A HUGE STEP )N FACT WE CHEATED A LITTLE BECAUSE ITS ACTUALLY TWO STEPS
!PPLICATION !SSEMBLY AND $EPLOYMENT
5!PPLICATION !SSEMBLY
4HIS MEANS TAKING THE BEAN FROM THE REUSABLE COMPONENT STAGE TO BEING PART OF
AN APPLICATION &OR SIMPLE BEANS THAT MIGHT MEAN SIMPLY WRITING A CLIENT THAT
CAN ACCESS THE BEAN IE CALL THE BEANS BUSINESS METHODS )N OTHER WORDS A
SINGLE BEAN MIGHT BE THE ENTIRE APPLICATION ON THE SERVER SIDE "UT THIS COULD
ALSO BE THE STEP WHERE YOU INTEGRATE MULTIPLE BEANS AND OTHER *AVA CLASSES
INTO A CUSTOM APPLICATION AND THAT USUALLY MEANS TAKING DIFFERENT BEANS EACH
IN ITS OWN EJB JAR WITH ITS OWN $$ AND PUTTING THEM INTO A NEW SINGLE EJB JAR
WITH A SINGLE $$ THAT MIGHT DESCRIBE HOW TWO OR MORE BEANS ARE RELATED TO ONE
ANOTHER
$URING ASSEMBLY YOU MIGHT ALSO ADD NEW INFORMATION TO THE $$ FOR THINGS THE
BEAN DEVELOPER DIDNT KNOW ABOUT &OR EXAMPLE THE BEAN DEVELOPER MIGHT
WRITE CODE THAT USES A SPECIAL BEAN SPECIlC hPROPERTYv CALLED AN ENVIRONMENT
ENTRY WHICH WELL GET INTO IN A LATER CHAPTER FOR THE TAX AMOUNT USED BY THIS
APPLICATION "UT THE BEAN DEVELOPER HAS NO IDEA WHAT VALUE TO GIVE THE TAX
AMOUNT PROPERTY SO HE LEAVES THE VALUE BLANK IN THE $$ 4HEN THE APPLICATION
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5$EPLOYMENT
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DEVELOPER MEETS THE SYS ADMIN 4HE TWO CRUCIAL PARTS OF DEPLOYMENT ARE NAMING
THE BEAN SO THE CLIENT WILL KNOW HOW TO lND IT AND GETTING THE BEAN INTO THE
CONTAINERS CONTROL
4HE SPEC DOESNT SAY ANYTHING ABOUT THE WAY IN WHICH YOU DEPLOY YOUR BEANS IT
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 26
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&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 27
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 28
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7ELL WRITE THE CODE COMPILE IT START THE SERVER START THE
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EJB JAR DEPLOY THE BEAN CREATE A CLIENT AND TEST THE BEAN
USING THE CLIENT 4HE ONLY THING WE WONT DO IS INSTALL AND
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)F YOU DONT YET HAVE THE *%% 2) UP AND RUNNING GO
TO HTTPJAVASUNCOMJEE AND DOWNLOAD VERSION OF *%% IT INCLUDES SET UP INSTRUCTIONS THEN GO BACK AND
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know
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 29
LQWURWR(-%
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!LL THE BEANS IN THIS BOOK ARE ORGANIZED INTO PACKAGES WHICH MEANS YOU
MUST BE A LITTLE MORE CAREFUL ABOUT COMPILING AND RUNNING %VERY INSTRUCTION
IN THIS CHAPTER ASSUMES YOUVE ORGANIZED YOUR PROJECT EXACTLY THE WAY ITS
SHOWN HERE )F YOU DEVIATE FROM THIS STRUCTURE YOURE ON YOUR OWN FOR
MAPPING OUR COMMAND LINE AND DEPLOYMENT FORMULAS TO YOUR OWN STRUCTURE
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 30
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 31
Return to Table of Contents
LQWURWR(-%
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/PEN UP A NEW TERMINAL FOR THE SERVER 9OULL LEAVE IT RUNNING AND WE
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 32
Return to Table of Contents
VWDUWLQJGHSOR\WRRO
;\IZ\LMXTWa\WWT
/PEN UP A NEW TERMINAL FOR THE DEPLOYTOOL 4HIS TOOL IS
PART OF THE *%% 2) AND IT HAS EVERYTHING YOU NEED TO
CREATE THE EJB JAR THE $$ AND TO DO THE lNAL DEPLOYMENT
INTO THE 2) SERVER
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7\SHµGHSOR\WRROKHOS¶IRUFRPPDQGOLQH
RSWLRQV
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! LOVELY SPLASH SCREEN POPS UP AND SITS WHILE THE
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DISAPPEARS SO DONT PANIC IF IT THEN LOOKS LIKE NOTHINGS
HAPPENING 0ATIENCE
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 33
LQWURWR(-%
5ISMIVM_)XXTQKI\QWV
4HE 2) IS A *%% SERVER REMEMBER NOT JUST AN %*" CONTAINER
3O WE HAVE TO DO A SMALL BIT OF *%%ISH STUFF BEFORE WE CAN
MAKE THE EJB JAR AND DEPLOY THE APP 4HIS STEP IS WHERE
WE CREATE A NEW *%% APPLICATION AND FOR NOW YOU CAN
THINK OF THE *%% APPLICATION AS SOMETHING THAT WRAPS THE
BEANS AND ADDS A LITTLE MORE INFORMATION FOR THE SERVER
4HE MAIN DIFFERENCE BETWEEN A *%% APPLICATION AND AN
%*" APPLICATION IS THAT A *%% APPLICATION CAN INCLUDE WEB
COMPONENTS SERVLETS AND *30S AS WELL AS %*" COMPONENTS
ALL INTEGRATED AS PART OF A SINGLE APP
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COMPONENTS ARE MORE TIGHTLY
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CAN HAVE ALL OF THE COMPONENTS
RESPECT ONE ANOTHERS TRANSAC
TIONS AND SECURITY "UT YOURE
ALWAYS FREE TO USE A SERVLET AS
A CLIENT TO AN ENTERPRISE BEAN
EVEN IF THAT BEAN ISNT RUNNING
IN THE SAME APPLICATION SERVER
OR EVEN THE SAME PHYSICAL
MACHINE !NOTHER ADVANTAGE
OF A *%% SERVER IS THE EASE WITH
WHICH YOU CAN DEPLOY BOTH
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ING %*" APPLICATIONS YOU ARE
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 34
GHSOR\WRROPDNLQJDQHZDSSOLFDWLRQ
6IUMIVL[I^M\PMVM_IXXTQKI\QWV
4HIS PARTS A LITTLE AWKWARD 9OU CAN USE THE "ROWSE BUTTON TO NAVIGATE
THROUGH YOUR OWN DIRECTORY TREE BUT THE EASIEST WAY TO NAME AND
SAVE THE APPLICATION IS TO TYPE THE COMPLETE PATH TO THE lLE YOURE
ABOUT TO CREATE 4HE THING WERE MAKING IS NOT THE BEAN ITSELFˆYOU
CAN THINK OF IT MORE LIKE A DOCUMENT THAT HOLDS ALL THE INFORMATION
ABOUT THE APPLICATION !S A CONVENTION WE SAVE THE APPLICATION IN
THE PROJECTS;WHATEVER= DIRECTORYˆTHE DIRECTORY CORRESPONDING TO
THAT PARTICULAR PROJECT &OR THE !DVICE BEAN THAT MEANS THE PROJECTS
ADVICE DIRECTORY )F YOU STARTED THE SERVER FROM THE PROJECTSADVICE
DIRECTORY IN OTHER WORDS IF ADVICE IS YOUR CURRENT WORKING DIRECTORY
THEN YOULL GET THE RIGHT NAME AND LOCATION BY DEFAULT
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&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 35
Return to Table of Contents
LQWURWR(-%
?PI\aW]¼TT[MMIN\MZaW]KZMI\MIVLVIUM
\PMIXXTQKI\QWV
.OW YOURE BACK AT THE MAIN SCREEN OF THE DEPLOYTOOL 9OU MIGHT
HAVE TO CLICK ON THE &ILES OR !PPLICATIONS ICONS TO EXPAND THEM BUT
YOULL SEE THAT THE TOOL HAS CREATED AN !PPLICATIONS DIRECTORY WITH
SOMETHING CALLED !DVICE!PP INSIDE #LICK ON THE !DVICE!PP ICON
AND YOULL SEE INFORMATION ABOUT THE APPLICATION INCLUDING THE
NAME LOCATION AND CURRENT CONTENTS !T THIS POINT THERES NOTHING
BUT A -%4! ).& DIRECTORY THAT HOLDS MORE INFO ABOUT THE APP
WHICH WE WONT EVER NEED TO LOOK AT &OLFNRQWKH$GYLFH$SSLFRQ
\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 36
Return to Table of Contents
GHSOR\WRROPDNLQJDQHZHQWHUSULVHEHDQ
6W_TM\¼[UISM\PMVM_MV\MZXZQ[M
JMIV\PMMRJRIZIVL\PM,,
4HIS IS WHAT WERE REALLY AFTERˆTHE ACTUAL BEAN 4HE PREVIOUS
STEPS MAKING THE *%% APPLICATION WERE TO SATISFY THE *%% 2)
BECAUSE WE HAVE TO DEPLOY THE BEAN WITHIN A *%% APP
&KRRVH)LOH1HZ(QWHUSULVH%HDQ
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 37
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LQWURWR(-%
6W__M¼ZMQV\PMZMITTaKWWT
6M_-V\MZXZQ[M*MIV?QbIZL
4HIS PART OF THE DEPLOYTOOL IS WHERE ALMOST EVERYTHING HAPPENS
4HE KEY THINGS WELL DO ARE
5 #REATE THE EJB JAR
5 0UT THE BEAN CLASS AND THE TWO INTERFACES INTO THE EJB JAR
5 #REATE THE DEPLOYMENT DESCRIPTOR THAT DESCRIBES THE BEAN
&OLFN1H[W!
\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 38
Return to Table of Contents
GHSOR\WRROFUHDWHDQHZHMEMDU
+ZMI\M\PMVM_MRJRIZ
&OR NOW JUST ACCEPT THE DEFAULTS 4HE RADIO BUTTON ON THE TOP LEFT OF
THE SCREEN SHOWS THAT YOURE MAKING A NEW *!2 WITHIN THE !DVICE!PP
APPLICATION .OTICE THAT THE !DVICE!PP IS PART OF A DROP DOWN LISTˆIF
THERE WERE OTHER EJB JARS ALREADY IN THE APPLICATION WE COULD HAVE
CHOSEN TO PUT THE NEW BEAN IN A PRE EXISTING *!2
4HE TOOL PICKS AN ESPECIALLY HELPFUL DISPLAY NAME h%JBv AND YOULL SEE
THIS BACK ON THE MAIN DEPLOYTOOL SCREEN WHEN WERE DONE 4HAT NAME
ISNT USED ANYWHERE IN YOUR REAL APPLICATION SO ITS NO BIG DEAL BUT IF
YOU HAVE MORE THAN ONE *!2 IN AN APPLICATION YOU MIGHT WANT TO GIVE IT
A MORE DESCRIPTIVE NAME #ART *!2 !CCOUNT *!2 ETC &OLFN(GLW
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 39
Return to Table of Contents
LQWURWR(-%
)LL\PM\PZMMKTI[[NQTM[QVKT]LQVO\PMQZ
XIKSIOMLQZMK\WZa\W\PM2):
4HIS IS THE MOST IMPORTANT PART OF THE WHOLE PROCESS )N OTHER WORDS DONT
SCREW IT UP 4HE KEY IS TO GET THE CORRECT CLASSES INTO THE *!2 IN THEIR PACKAGE
DIRECTORY STRUCTURE AND ONLY THEIR PACKAGE DIRECTORY STRUCTURE )N OTHER WORDS
IF YOU PUT THE THREE CLASS lLES INTO THE *!2 WITHOUT THE HEADlRST DIRECTORY
YOUR BEAN WONT DEPLOY /R IF YOU INCLUDE THE CLASSES DIRECTORY AS WELL AS THE
HEADlRST DIRECTORY YOUR BEANS WONT DEPLOY 2EMEMBER THE EJB JAR IS STILL A
*!2 lLE SO THE USUAL *!2 RULES ABOUT PACKAGE STRUCTURES APPLY HERE
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 40
Return to Table of Contents
GHSOR\WRROFRQ¿UP-$5FRQWHQWV
+WVNQZU\PI\aW]ILLML764A\PM
XIKSIOMLQZMK\WZaIVL\PMKTI[[NQTM[
9OU GOTTA GET THIS PART RIGHT ,OOK AT THE BOTTOM WINDOW THAT SAYS h#ONTENTS OF
%JBv AND VERIFY THAT THE ONLY THING IN THE *!2 BESIDES THE -%4! ).& DIRECTORY
IS THE HEADlRST DIRECTORY INCLUDING THE CONTENTS OF THE DIRECTORY 4HE CLASSIC
MISTAKE WE SEE ALL THE TIME NOT THAT YOUD EVER DO THAT IS TO ADD ONLY THE CLASS lLES
BUT NOT THE PACKAGE DIRECTORY "E SURE THAT YOU HAVE THE HEADlRST DIRECTORY AND
NOT THE CLASSES DIRECTORY WITH THE THREE CLASS lLES !NOTHER COMMON MISTAKE IS TO
ADD THE SOURCE lLES INSTEAD OF THE CLASS lLES 3O DONT FEEL BAD IF IT HAPPENS TO YOU
9HULI\WKDW\RXKDYHWKHULJKWFODVVHV DQGSDFNDJHGLUHFWRU\
,I\RXGRQ¶WVHOHFWWKHPIURPWKHERWWRPZLQGRZFOLFN5HPRYHDQGVWDUWRYHU
&OLFN2.ZKHQ\RX¶UHGRQHWKHQFOLFN1(;7
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 41
Return to Table of Contents
LQWURWR(-%
5ISMQ\I;\I\MTM[[;M[[QWVJMIV
.OW WERE AT THE PLACE WHERE WE GIVE THE TOOL THE BEANS @STRUCTURAL INFORMATION 7HAT KIND OF
BEAN IT IS WHICH CLASS lLE IS THE HOME INTERFACE AND SO ON 2EMEMBER THE TOOL USES THIS TO CREATE
THE DEPLOYMENT DESCRIPTOR !ND THE %*" CONTAINER USES THE DEPLOYMENT DESCRIPTOR TO lGURE OUT
HOW TO DEPLOY AND MANAGE THE BEAN
4HE !DVICE BEAN IS SIMPLEˆCLIENT CALLS A METHOD ON THE REMOTE OBJECT THE REMOTE OBJECT RETURNS
A VALUE THEN THE REMOTE OBJECT FORGETS THE WHOLE THING EVER HAPPENED %ND OF STORY 4HAT SCENARIO
IS JUST PERFECT FOR A STATELESS SESSION BEAN SOLUTION )F THE !DVICE BEAN NEEDED TO REMEMBER THE ADVICE
IT GAVE TO THE CLIENT AND USE IT IN SOME WAY IN FUTURE INVOCATIONS FROM THAT SAME CLIENT THEN WED
MAKE IT STATEFUL "UT WE DONT SO WE WONT
!ND AS YOULL LEARN LATER IT WOULDNT MAKE SENSE TO HAVE THE !DVICE BEAN BE AN ENTITY OR MESSAGE
DRIVEN BEAN "UT ITS TOO LATE TO MAKE IT ANYTHING BUT A SESSION BEAN ANYWAYˆYOUR BEAN CLASS
IMPLEMENTS THE 3ESSION"EAN INTERFACE 3O YOURE ALREADY COMMITTED TO A BEAN TYPE "UT WHETHER
THE SESSION BEAN IS STATELESS OR STATEFUL CAN BE A LITTLE MORE SUBTLE &OR NOW JUST MAKE IT STATELESS
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 42
Return to Table of Contents
GHSOR\WRROUHODWLQJWKHEHDQ¶VFODVV¿OHV
<MTTQ\_PQKPWN\PM\PZMMKTI[[NQTM[QV\PM2):
Q[\PMIK\]IT*-)6KTI[[
9OU HAVE THREE CLASS lLES IN THE *!2 THE HOME INTERFACE !DVICE(OME THE
COMPONENT INTERFACE !DVICE AND THE BEAN !DVICE"EAN "UT THE %*"
CONTAINER NEEDS TO KNOW WHICH IS WHICH 2EMEMBER THE NAMING CONVENTION
DOESNT MEAN ANYTHING TO ANYONE BUT YOU 4HE CONTAINER WONT LOOK AT THE
THREE CLASSES IN THE *!2 AND RECOGNIZE THAT !DVICE(OME MUST BE THE HOME
INTERFACE AND SO ON .O THE NAMING CONVENTION IS FOR YOU AND ANYONE ELSE
USING YOUR BEAN COMPONENTS
3O NOW YOU HAVE TO TELL THE TOOL WHICH OF THE lLES IS THE BEAN CLASS WELL DO
THE TWO INTERFACES ON THE NEXT PAGE 4HE TOOL THEN WILL PUT THIS INFO INTO
THE DEPLOYMENT DESCRIPTOR
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&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 43
LQWURWR(-%
<MTTQ\_PQKPQ[\PM0WUMQV\MZNIKMIVL_PQKP
Q[\PM+WUXWVMV\QV\MZNIKM
.OW YOU HAVE TO DO THE SAME THING YOU DID FOR THE BEAN CLASS BUT WITH THE TWO
INTERFACES 9OULL NOTICE THAT THERE ARE TWO DIFFERENT PLACES WHERE YOU CAN SELECT
INTERFACESˆ,OCAL AND 2EMOTE 4HIS BEAN IS REMOTE WHICH MEANS ITS A *AVA 2-)
REMOTE SERVICE BUT WELL GET INTO THAT IN THE NEXT CHAPTER SO WERE USING ONLY THE
BOTTOM SECTION FOR 2EMOTE INTERFACES *UST LEAVE THE ,OCAL INTERFACES SECTION ALONE
4HE STRANGE PART IS THAT THIS SCREEN USES THE TERM 2EMOTE )NTERFACE RATHER THAN
2EMOTE #OMPONENT )NTERFACE 4HATS JUST A BAD INTERFACE DESIGN IN THE DEPLOYTOOL
)TS ACTUALLY AN ARTIFACT OF THE PREVIOUS VERSION OF %*" WHEN THERE WERE ONLY REMOTE
INTERFACES ,OCAL INTERFACES ARE NEW TO %*" BUT WE HAVE TO LIVE WITH IT
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6HOHFWKHDGÀUVW$GYLFH
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 44
GHSOR\WRROYHULI\VWUXFWXUDOLQIRUPDWLRQ
>MZQNaM^MZa\PQVOWV\PQ[[KZMMV
#HOOSING THE BEAN CLASS THE HOME INTERFACE AND THE COMPONENT INTERFACE IS A
PERMANENT DECISION /NCE YOURE DONE WITH THE REST OF THE BEAN WIZARD AND THE
DEPLOYMENT DESCRIPTOR IS CREATED YOURE STUCK WITH IT )F YOU ACCIDENTALLY MIX UP
THE HOME AND COMPONENT INTERFACES YOUR BEAN WONT WORK )N THE 2) IT WONT EVEN
DEPLOY SOME SERVERS LET YOU DEPLOY STRUCTURALLY BAD BEANS WHICH MEANS THEY BLOW UP
AT RUNTIME BUT THE 2) WONT EVEN LET YOU IN THE SERVER DOOR %HVXUH\RXKDYHWKHIROORZLQJVHWWLQJV
(QWHUSULVH%HDQ&ODVVKHDGÀUVW$GYLFH%HDQ
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 45
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LQWURWR(-%
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"ECAUSE THIS BEAN IS SO SIMPLE AND WE DONT CARE ABOUT TRANSACTIONS SECURITY
ENVIRONMENT ENTRIES AND DATABASE ACCESS WEVE DONE EVERYTHING WE NEED TO
MAKE THE DEPLOYMENT DESCRIPTOR AND PUT IT IN A *!2 WITH THE CLASS lLES
3O YOU CAN IGNORE THE 4RANSACTIONS -ANAGEMENT SCREEN ALTHOUGH YOULL
BECOME INTIMATE WITH IT LATER IN THE BOOK
&OLFN)LQLVK
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 46
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GHSOR\WRROPDLQVFUHHQDIWHUPDNLQJDEHDQ
5MIV_PQTMJIKSWV\PMUIQVLMXTWa\WWT[KZMMV
4HINGS HAVE CHANGED 4HE !DVICE!PP ICON EXPANDS TO SHOW YOUR EJB JAR
NAMED h%JBv AND THE EJB JAR EXPANDS TO SHOW THE CUTE BEAN ICON NAMED
h!DVICE"EANv )F YOU SELECT THE !DVICE"EAN YOULL SEE A BUNCH OF TABBED PANELS
THATLL SHOW YOU THE CHOICES YOU MADE IN THE BEAN WIZARD 3OME OF THE THINGS YOU
CHOSE CAN BE CHANGED BUT SOME CANT )N THE 'ENERAL PANEL FOR EXAMPLE YOU
CANT CHANGE THE CLASS lLE DESIGNATIONS FOR THE HOME COMPONENT AND BEAN )N
FACT YOU CAN SEE THAT THE DROP DOWN LISTS FOR THESE ARE GRAYED OUT HERE "UT GEE
YOU CAN STILL CHANGE IT FROM 3TATELESS TO 3TATEFUL
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 47
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LQWURWR(-%
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9OU ALREADY KNOW YOUR BEAN CLASSES COMPILE BUT JUST BECAUSE IT COMPILES
DOESNT MEAN IT FOLLOWS BEAN LAW 4HE VERIlER TAKES YOUR JAR AND RUNS IT
THROUGH A BUNCH OF TESTS TO SEE IF IT MEETS THE MINIMUM REQUIREMENTS FOR
DEPLOYMENT !S YOU LEARN MORE ABOUT THE %*" SPEC YOULL SEE THAT THE
VERIlER IS TESTING YOUR BEANS CODE AND THE DEPLOYMENT DESCRIPTOR TO SEE
IF IT COMPLIES WITH THE SPEC &OR EXAMPLE A STATELESS SESSION BEANS HOME
INTERFACE MUST HAVE A NO ARG CREATE METHOD DECLARED AND NOTHING ELSE
!ND THE BEAN CLASS MUST HAVE METHODS THAT MATCH THOSE DECLARED IN THE
COMPONENT INTERFACE !ND IF THE COMPONENT INTERFACE IS REMOTE IT MUST
DECLARE THAT EACH METHOD THROWS 2EMOTE%XCEPTION $ONT WORRY ABOUT
REMEMBERING THESE EXAMPLES ITS JUST TO GIVE YOU AN IDEA OF THE KINDS OF
THINGS THE VERIlER DOES
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 48
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GHSOR\WRROUXQQLQJWKHYHUL¿HU
+TW[MaW]ZMaM[IVLKTQKS73
4HE VERIlER SCREEN SHOWS YOU THE NAME OF THE *!2 AS EJB JAR ICJAR IN A TMP
DIRECTORY BUT THATS JUST HOW THE 2) SAVES YOUR EJB JAR UNTIL YOURE READY TO
DEPLOY 4HE TMP lLE AND THE *!2 WILL GO AWAY WHEN YOU DEPLOY OR DELETE
THE BEAN FROM YOUR APPLICATION
!T LEAST ITS SUPPOSED TO 3OMETIMES YOU MIGHT HAVE TO lND THAT DIRECTORY AND
DELETE IT YOURSELF 2EPEAT AFTER ME 4HE DEPLOYTOOL IS FREE 4HE DEPLOYTOOL IS
NOT A PRODUCTION TOOL ) DID NOT PAY ANY MONEY FOR THIS TOOL ) WILL LEARN TO
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 49
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LQWURWR(-%
?PM_ 6WNIQTML\M[\[
)F EVERYTHING VERIlES YOU SEE A NICE LITTLE MESSAGE IN THE $ETAILS BOX AT THE BOTTOM OF THE
VERIlER WINDOW )F THERE ARE FAILURES YOULL SEE THEM IN THE 2ESULTS BOX 9OU CAN CLICK ON A
@FAILURE MESSAGE TO GET MORE DETAILS ABOUT WHAT WENT WRONG $ONT PANIC IF YOU SEE A MILLION
FAILURES USUALLY YOU CAN lX ONE THING AND THEY ALL GO AWAY 5NLIKE COMPILER ERROR MESSAGES
WHICH ARE SOMETIMES ABOUT AS HELPFUL AS 6#2 INSTRUCTIONS THE VERIlER FAILURE MESSAGES ARE
PRETTY EXPLICIT 9OU CAN USUALLY lGURE OUT EXACTLY WHERE YOU WENT WRONG
3OMETIMES YOU CAN lX THE PROBLEM BACK IN THE MAIN DEPLOYTOOL WINDOW BY CLICKING ON ONE OF
THE TABBED PANELS AND CHANGING SOMETHING &OR EXAMPLE IF YOU FORGOT TO SPECIFY A TRANSACTION
ATTRIBUTE FOR AN ENTITY BEAN METHOD YOU CAN GO TO THE 4RANSACTIONS TABBED PANEL IN THE
DEPLOYTOOL WINDOW AND SET THE ATTRIBUTE WITHOUT STARTING OVER IN THE BEAN WIZARD
"UT IF YOU HAVE PROBLEMS WITH YOUR ACTUAL CLASS lLES YOULL HAVE TO MODIFY THEM RECOMPILE
THEM AND THEN UPDATE YOUR EJB JAR /R IF THE PROBLEM IS THAT YOU MADE A SETTING IN THE BEAN
WIZARD THAT CANT BE CHANGED LIKE SELECTING THE BEAN CLASS WHEN THE TOOL ASKS FOR THE HOME
INTERFACE YOULL HAVE TO DELETE THE EJB JAR AND START OVER WITH THE BEAN WIZARD
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 50
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GHSOR\WRROGRLQJWKHGHSOR\
<QUM\W,MXTWa
/NCE YOUVE VERIlED YOURE READY TO DEPLOY 4HERES NOT MUCH THAT CAN GO
WRONG UNLESS SOMETHING BAD HAPPENS IN THE SERVER !T THIS POINT ALMOST
ANYTHING THAT GOES WRONG CAN BE lXED BY SHUTTING DOWN THE SERVER AND
DEPLOYTOOL AND STARTING THEM BACK UP AGAIN $RASTIC YES BUT IT USUALLY WORKS
3OMETIMES YOU DO HAVE TO TAKE EVEN HARSHER ACTION BY RETURNING THE SERVER
BACK TO ITS FRESHLY INSTALLED STATE BUT FORTUNATELY THERES A COMMAND THAT
CAN DO THAT 7HEN ALL ELSE FAILS BRING UP A NEW TERMINAL AND TYPE CLEANUP
4HIS SCRIPT SHUTS DOWN THE *%% SERVER BUT IT ALSO CLEANS OUT ALL THE LOGS
DIRECTORIES AND lLES THAT HAVE BEEN MADE ON THAT MACHINE !FTER THAT YOU
CAN TRY STARTING THE SERVER THEN THE DEPLOYTOOL AND DEPLOYING AGAIN !ND IF
YOU EVER OPEN THE DEPLOYTOOL AND YOU DONT SEE YOUR APPLICATION DONT PANIC
*UST GO TO THE &ILE MENU AND CHOOSE /PEN JUST LIKE YOU WOULD TO OPEN A
DOCUMENT IN ANY OTHER APPLICATION 4HINK OF THE *%% APP LIKE A DOCUMENT AS
FAR AS THE DEPLOYTOOL IS CONCERNED
&KRRVH7RROV 'HSOR\
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 51
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LQWURWR(-%
5ISMQ\:M\]ZVI+TQMV\2IZ
/NCE IT STARTS THE SERVER IS GOING TO DO A TON OF THINGS TO GET YOUR BEAN READY /NE OF
THEM IS TO GENERATE THE CLASS lLES THAT IMPLEMENT YOUR TWO INTERFACES THE HOME AND THE
COMPONENT INTERFACES !ND SINCE THEYRE REMOTE INTERFACES THE SERVER WILL ALSO CREATE
THE REMOTE STUB CLASSES FOR THOSE INTERFACES ,OTS MORE ON THESE LATER 7ELL THE CLIENT
NEEDS THE TWO INTERFACES AND THE TWO STUBS 9OU COULD HAVE GIVEN THE CLIENT THE INTERFACES
SINCE YOU CREATED THOSE "UT ONLY THE SERVER CAN MAKE THE STUB CLASSES AND THE CLIENT WILL
NEVER WORK WITHOUT THEM 3O YOUR CLIENT APPLICATION MIGHT BE SITTING THERE ALL NICE AND
COMPILED AND JUST WAITING FOR YOU TO GIVE IT THE STUB CLASSES SO THAT IT CAN ACTUALLY RUN
&ORTUNATELY YOU CAN ASK THE 2) DEPLOYTOOL TO GIVE YOU A CLIENT JAR THAT HAS EVERYTHING THE
CLIENT NEEDS AND A LOT MORE IT TURNS OUT BUT SINCE THIS ISNT A REAL PRODUCTION ENVIRONMENT
WERE JUST GOING TO LET THAT GO 6IRTUALLY ALL %*" APPLICATION SERVERS MUST CREATE THE STUB CLASSES SO YOULL HAVE TO lND OUT
WHERE YOUR SERVER PUTS THEM SO YOU CAN GIVE THEM TO THE CLIENT
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 52
GHSOR\WRROJLYLQJWKHEHDQD-1',QDPH
/Q^MQ\IVIUM[WKTQMV\[KIVTWWSQ\]X
7ERE NOW DANGEROUSLY CLOSE TO DEPLOYMENT AND THE LAST STEP IS TO GIVE THE BEAN A
*.$) NAME 4HATS THE NAME CLIENTS USE TO GET A REFERENCE TO THE BEAN 7ELL TO WHAT
THE CLIENT THINKS IS THE BEAN BUT WELL SAVE THE GORY DETAILS FOR THE NEXT CHAPTER
4HE BEANS *.$) NAME IS SIMPLY THE LOGICAL NAME YOU CHOOSE OR IN THE REAL WORLD
WHOEVER DEPLOYS THE BEAN )T DOESNT HAVE TO MATCH ANYTHING FROM THE BEAN ITSELF 7E
COULD FOR EXAMPLE NAME THIS BEAN (OMER WHICH WOULD IN FACT MAKE IT EVEN MORE
FUN AND CHALLENGING FOR THE CLIENTS THAN IT ALREADY WOULD BE WITH A MEANINGFUL NAME
7\SHLQWKH-1',QDPH$GYLVRU
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&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 53
LQWURWR(-%
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7AIT FOR IT WAIT FOR IT WAIT FOR IT
7HEN THE BEANS DEPLOYED SUCCESSFULLY YOULL SEE THE LINE h$EPLOYMENT OF !DVICE!PP
IS COMPLETEv IN THE WINDOW !T THAT POINT CLIENTS CAN ACCESS THE BEAN
9OU DID IT
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ItÕs a miracle!
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\RXDUHKHUH
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Page 54
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GHSOR\WRROPDLQVFUHHQDIWHUGHSOR\LQJ
6W_aW]¼TT[MM\PM)L^QKM)XXQV[QLM\PM[MZ ^MZ
5NDER THE 3ERVERS ICON YOULL SEE THE LOCALHOST ICON REPRESENTING THE *%% SERVER
YOU STARTED BEFORE YOU LAUNCHED THE DEPLOYTOOL !ND UNDER THE LOCALHOST ICON YOU
CAN NOW SEE THAT YOUR !DVICE!PP IS DEPLOYED 9OULL ALSO SEE THE 5NDEPLOY BUTTON
THAT YOU CAN USE TO WELL UNDEPLOY
([SDQGWKH6HUYHUV!ORFDOKRVWLFRQVWRVHHWKH$GYLFH$SS
&KDSWHU
Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 55
LQWURWR(-%
6W_ITT_MVMMLQ[IKTQMV\
7E HAVE A FRESHLY DEPLOYED BEAN IN A *%% SERVER BUT WE CANT
TEST IT UNTIL WE HAVE A CLIENT 4HE CLIENT HAS TO DO lVE THINGS
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 56
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 1. Welcome to EJB
Return to Table of Contents
Page 57
LQWURWR(-%
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 59
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 60
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Chapter 1. Welcome to EJB
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Table of Contents
Chapter 2. EJB Architecture........................................................................ 1
Section 2.1. objectives Background................................................................................................................................................. 2
Section 2.2. You remember this picture......................................................................................................................................... 3
Section 2.3. Making a remote method call..................................................................................................................................... 4
Section 2.4. There's a "helper" on the server as well...................................................................................................................... 5
Section 2.5. There are no dumb questions..................................................................................................................................... 6
Section 2.6. What about and return values arguments?................................................................................................................ 7
Section 2.7. What really gets passed when you pass an object to a remote method?.................................................................... 9
Section 2.8. There are no Dumb Questions.................................................................................................................................. 12
Section 2.9. Passing a Remote object through a remote method call.......................................................................................... 14
Section 2.10. Brain power.............................................................................................................................................................. 15
Section 2.11. There are no Dumb Question................................................................................................................................... 17
Section 2.12. What must the Remote object and the stub have in common?.............................................................................. 19
Section 2.13. The client calls business methods on the stub through the Remote business interface....................................... 20
Section 2.14. Sharpen your pencil................................................................................................................................................. 21
Section 2.15. How EJB uses RMI.................................................................................................................................................. 22
Section 2.16. The Remote object is not the bean, it's the bean's bodyguard—the EJBObject .................................................... 23
Section 2.17. The Component interface........................................................................................................................................ 24
Section 2.18. There are no Dumb Questions................................................................................................................................ 26
Section 2.19. Who writes the class that really DOES implement the component interface? In other words, who makes the
EJBObject class?........................................................................................................................................................................... 28
Section 2.20. Who creates what?.................................................................................................................................................. 29
Section 2.21. THE TIKIBEAN LOUNGE...................................................................................................................................... 30
Section 2.22. There are no Dumb Questions................................................................................................................................ 31
Section 2.23. Sharpen your pencil................................................................................................................................................ 37
Section 2.24. Architectural over view: Session beans.................................................................................................................. 39
Section 2.25. Architectural overview: Entity beans..................................................................................................................... 40
Section 2.26. Architectural overview : Creating a Stateful Session bean..................................................................................... 41
Section 2.27. Architectural overview: Creating a Stateless Session bean.................................................................................... 42
Section 2.28. Who creates the stateless session bean, and when?.............................................................................................. 43
Section 2.29. Stateless session beans are more scalable.............................................................................................................. 44
Section 2.30. Brain power............................................................................................................................................................. 45
Section 2.31. there are no Dumb Questions................................................................................................................................. 45
Section 2.32. Sharpen your pencil................................................................................................................................................ 45
Section 2.33. There are no Dumb Questions................................................................................................................................ 46
Section 2.34. Architectural over view: Message-driven beans..................................................................................................... 47
Section 2.35. Exercise: What goes where?................................................................................................................................... 48
Section 2.36. Exercise: Organize your beans................................................................................................................................ 49
Section 2.37. Exercise Solutions: What goes where?................................................................................................................... 50
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Page 1
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 2
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 2. EJB Architecture
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Page 3
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 4
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 5
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 6
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WAYS A LOCAL METHOD CALL WOULD NOT AND THE CLIENT
NEEDS TO BE PREPARED FOR THAT
4HATS WHY IN *AVA 2-) ALL REMOTE METHODS MUST
DECLARE A JAVARMI2EMOTE%XCEPTION WHICH IS A
CHECKED EXCEPTION 4HAT MEANS THE CLIENT HAS TO
HANDLE OR DECLARE THE EXCEPTION )N OTHER WORDS
THE CLIENT CANT REALLY PRETEND THE METHOD CALL ISNT
REMOTE
"UT WAIT THERES MOREˆTHE CLIENT HAS TO DO
SOMETHING SPECIAL TO EVEN GET THE REFERENCE TO THE
2EMOTE OBJECT IN THE FIRST PLACE !ND WHAT EXACTLY IS
THAT REFERENCE )TS REALLY A REFERENCE TO THE 2EMOTE
OBJECTS PROXYˆTHE STUB
3O NO 2-) DOES NOT GIVE YOU TRUE NETWORK
TRANSPARENCY 4HE DESIGNERS OF 2-) WANT THE CLIENT
TO ACKNOWLEDGE THAT THINGS CAN GO HORRIBLY WRONG
WITH A REMOTE METHOD INVOCATION
3TILL WHEN YOU LOOK AT EVERYTHING THAT NEEDS TO
HAPPEN TO MAKE A REMOTE METHOD CALL NETWORKING
3OCKET CONNECTION STREAMS PACKAGING UP
ARGUMENTS ETC THE CLIENT HAS TO DO ONLY A COUPLE
OF THINGS USE A SPECIAL LOOKUP PROCESS TO GET THE
REFERENCE TO THE REMOTE OBJECT AND WRAP REMOTE
METHOD CALLS IN A TRYCATCH 4HATS PRETTY TRIVIAL
WHEN YOU CONSIDER WHAT IT WOULD TAKE IF THE CLIENT
HAD TO MANAGE THE WHOLE PROCESS
!M ) RESPONSIBLE FOR BUILDING THE STUB
AND THE SKELETON (OW DOES THE STUB KNOW WHAT
METHODS MY 2EMOTE OBJECT HAS &OR THAT MATTER
HOW DOES THE CLIENT KNOW WHAT METHODS MY
2EMOTE OBJECT HAS
.O YOU DONT NEED TO MAKE THE STUBS AND
SKELETONS 7ITH PLAIN OLD 2-) YOU USE THE 2-)
COMPILER RMIC TO GENERATE THEM "UT FOR THE OTHER
TWO QUESTIONS WELL LET YOU THINK ABOUT IT FOR A
MINUTE BEFORE WE LOOK AT THE DETAILS
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!ND THERES EVEN A WAY TO MAKE IT EASIER FOR THE
CLIENT USING AN %*" DESIGN PATTERN WELL SEE IN THE
LAST CHAPTER &KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 7
DUFKLWHFWXUDORYHUYLHZ
?PI\IJW]\IZO]UMV\[IVLZM\]ZV^IT]M['
2EMOTE METHOD CALLS ARE JUST LIKE LOCAL METHOD CALLS EXCEPT FOR THE
2EMOTE%XCEPTIONS !ND WHAT GOOD WOULD A METHOD CALL BE IF YOU
COULDNT PASS ARGUMENTS OR GET A RETURN VALUE 9OU MIGHT AS WELL BE
DOING 20# THE WAY YOUR PARENTS DID
4HIS BRINGS US TO ONE OF THE KEY JOBS FOR THE STUB AND THE SKELETON OR
WHATEVER IS DOING THE SKELETONISH THINGS ˆPACKING AND UNPACKING
VALUES SHIPPED OVER THE WIRE
2EMEMBER THE CLIENT IS REALLY CALLING A METHOD ON THE STUB AND THE
STUB IS LOCAL TO THE CLIENT IE IN THE SAME HEAP 3O FROM THE CLIENTS
PERSPECTIVE THERES NOTHING SPECIAL ABOUT SENDING ARGUMENTS WITH
THE METHOD )TS THE STUB THAT DOES ALL THE DIRTY WORK 4HE STUB HAS TO
PACKAGE UP THE ARGUMENTS THROUGH A PROCESS KNOWN AS MARSHALLING
AND SEND THEM IN THE OUTPUT STREAM THROUGH THE 3OCKET CONNECTION
WITH THE SERVER
4HE SKELETON THING ON THE SERVER HAS TO PROCESS THE STREAM FROM THE
STUB UNPACK THE ARGUMENTS lGURE OUT WHAT TO DO WITH EVERYTHING FOR
INSTANCE WHICH METHOD TO CALL ON WHICH OBJECT AND THEN INVOKE THE
METHOD A LOCAL CALL ON THE 2EMOTE OBJECT WITH THE ARGUMENTS
4HEN IT ALL HAPPENS IN REVERSE 4HE SKELETON PACKAGES UP THE RETURN
VALUES AND SHIPS THEM TO THE STUB WHO UNPACKS THEM AND GIVES THEM
TO THE CLIENT AS PLAIN OLD GARDEN VARIETY RETURN VALUES "UT IN ORDER TO
SEND ARGUMENTS AND RETURN VALUES THEY MUST BE PRIMITIVES 3ERIALIZABLE
OBJECTS AN ARRAY OR COLLECTION OF PRIMITIVES OR 3ERIALIZABLE OBJECTS OR A
2EMOTE OBJECT
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The skeleton (or whatever is doing the skeleton
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arguments for the Remote object method call, then
packs and ships the return value.
\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 8
SDVVLQJREMHFWVUHPRWHO\
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WeÕll think of
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call methods) on n use to push buttons (i.e.
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 9
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NOW what are we
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 10
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Client passes a co
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the Dog object on
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only one Dog object.
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 11
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\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 12
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A:
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)M SITTING HERE WITH A (ASH-AP FULL OF
3ERIALIZABLE #USTOMER OBJECTS WITH 3TRING KEYS
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ITSELF IS 3ERIALIZABLE
/+ THIS IS KIND OF A TRICKY ONE !LL OF THE
#OLLECTION IMPLEMENTATIONS IN THE *3% !0) ARE
3ERIALIZABLE 3O YOU DONT HAVE TO WORRY ABOUT A
(ASHMAPˆAS LONG AS WHAT YOU PUT IN THE (ASHMAP
IS 3ERIALIZABLE YOURE FINE
"UT THERE IS ONE PLACE WHERE THINGS CAN FAIL
#HANCES ARE YOULL NEVER SEE THIS BUT ITS STILL WORTH
MENTIONING 9OU PROBABLY ALREADY KNOW THAT THE
-AP CLASSES LIKE (ASH-AP AND (ASHTABLE HAVE A
VALUES METHOD THAT RETURNS A COLLECTION OF JUST
THE VALUES WITHOUT THE KEYS )N OTHER WORDS IF YOU
CALLED IT ON YOUR (ASH-AP YOUD GET A #OLLECTION OF
#USTOMER OBJECTS
"UT WHAT TYPE OF COLLECTION !ND THERES THE
PROBLEM 9OU DONT KNOW !LL YOU KNOW IS THAT
ITS SOMETHING THAT IMPLEMENTS THE #OLLECTION
INTERFACE "UT THAT ISNT ENOUGH TO TELL YOU WHETHER
THE #OLLECTION RETURNED BY VALUES IS 3ERIALIZABLE
)N OTHER WORDS YOU MIGHT GET BACK A #OLLECTION
THATˆEVEN WHEN FILLED WITH 3ERIALIZABLE OBJECTSˆIS
NOT ITSELF 3ERIALIZABLE
4HE BOTTOM LINE DONT RELY ON THE #OLLECTION
RETURNED FROM A MAPS VALUES METHOD TO BE
3ERIALIZABLE 0UT YOUR VALUES INTO SOMETHING YOU CAN
TRUST TO BE 3ERIALIZABLE LIKE !RRAY,IST BEFORE TRYING
TO SHIP THEM AS PART OF A REMOTE METHOD CALL
)F SOMETHING YOURE PASSING TO A REMOTE
METHOD ISNT 3ERIALIZABLE IS THIS A COMPILE TIME OR
RUNTIME FAILURE
2UNTIME 5SUALLY ANYWAY 2EMEMBER THAT THE
DECLARED ARGUMENT OR RETURN TYPE IS NOT NECESSARILY
THE SAME AS THE ACTUAL RUNTIME TYPE
4HE ONLY CASE WHERE IT CAN FAIL AT COMPILE TIME IS IF
THE REMOTE METHOD ACTUALLY USES 3ERIALIZABLE AS THE
DECLARED TYPE OF THE ARGUMENT OR RETURN VALUE
SXEOLFYRLGWDNH,W 6HULDOL]DEOHV )N THAT CIRCUMSTANCE THE COMPILER CAN USE NORMAL
*AVA TYPE CHECKING TO SEE IF THE DECLARED TYPE OF THE
THING BEING PASSED IMPLEMENTS 3ERIALIZABLE
-OST OF THE TIME THE DECLARED ARGUMENT OR RETURN
TYPE IS SOMETHING OTHER THAN 3ERIALIZABLE LIKE $OG
!RRAY,IST 3TRING ETC SO *AVA WONT KNOW WHETHER THE
RUNTIME OBJECT IS 3ERIALIZABLE UNTIL IT ACTUALLY TRIES TO
DO THE SERIALIZATION AND THEN IT THROWS AN EXCEPTION !ND WITH COLLECTIONS AND ARRAYS IF ANY OF THE OBJECTS
INSIDE ARENT 3ERIALIZABLE THE WHOLE SERIALIZATION FAILS
Q:
$OES MY CLASS HAVE TO EXPLICITLY IMPLEMENT
3ERIALIZABLE OR CAN ) INHERIT 3ERIALIZABLENESS FROM MY
SUPERCLASS
A:
2EMEMBER *AVAS )3 ! RULE IF YOUR PARENT
SUPERCLASS IS SOMETHING THEN SO ARE YOU )F $OG
EXTENDS !NIMAL AND !NIMAL IMPLEMENTS 3ERIALIZABLE
THEN $OG IS 3ERIALIZABLE WHETHER THE $OG CLASS
EXPLICITLY DECLARES IT OR NOT
(OWEVER IT IS CONSIDERED GOOD PRACTICE TO EXPLICITLY
DECLARE YOUR CLASS AS 3ERIALIZABLE EVEN IF YOUR SUPERCLASS
DOES JUST SO THAT OTHERS LOOKING AT YOUR CLASS !0) DONT
HAVE TO HUNT THROUGH YOUR CLASS INHERITANCE TREE TO SEE
IF SOMEBODY UP THERE IS 3ERIALIZABLE
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
Page 13
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ItÕll make sense in a minute.
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page, think about the
implications of passing a
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remote method call...
\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 14
UHPRWHPHWKRGDUJXPHQWV
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)T DOES NOT MAKE SENSE TO SEND A 2EMOTE OBJECT IN A
REMOTE METHOD CALL !FTER ALL THE WHOLE POINT OF A
2EMOTE OBJECT IS TO STAY REMOTE 4O BE ACCESSED BY
CLIENTS WHO LIVE SOMEWHERE ELSE )N ANOTHER HEAP
"UT WHAT IF YOU WANT TO PASS A REMOTE CLIENT A
REFERENCE TO ANOTHER 2EMOTE OBJECT 7HAT IF
RATHER THAN HANDING YOUR CLIENT A FULL BLOWN COPY
OF A #USTOMER YOU SEND HIM A STUB TO A 2EMOTE
#USTOMER
4HINK ABOUT IT "EFORE YOU READ THE NEXT PAGE
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 15
VWDWHIXODQGVWDWHOHVVVHVVLRQEHDQV
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7ELL GO OVER ALL THIS IN DETAIL IN THE 3ESSION "EAN
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BEANS CAN BE MARKED AT DEPLOYMENT TIME AS
EITHER STATELESS OR STATEFUL
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BETWEEN METHOD CALLS WHILE A STATELESS BEAN WONT
REMEMBER ANYTHING ABOUT THE CLIENT BETWEEN
METHOD INVOCATIONS
4HE PHRASE hCONVERSATIONAL STATEv REALLY MEANS
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A SHOPPING CART )T WOULDNT BE FUN IF YOU THE
SHOPPER GOT A CART PUT SOMETHING IN BUT THEN
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lRST THING VANISHES FROM THE CART .OT TOO USER
FRIENDLY 3O A GOOD SHOPPING CART WILL KEEP THE
CLIENT SHOPPER STATE IE THE ITEMS IN THE CART
FOR AS LONG AS THE SHOPPING SESSION IS ALIVE 7ELL
EXPLAIN WHAT WE MEAN BY ALIVE IN THE 3ESSION "EAN
CHAPTER
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ONCE THE METHOD CALL COMPLETES 3O STATELESS
BEANS ARE FOR SERVICES THAT DONT REQUIRE A
CONTINUED CONVERSATION BETWEEN THE CLIENT AND
THE SERVICE 4HAT DOESNT MEAN THE CLIENT WONT
KEEP CALLING METHODS ON THE STATELESS BEAN BUT
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FOR SAVING THAT STATE LIKE USING
THE CLIENT TO STORE STATE OR USING
A SERVLET TO STORE STATE OR USING A
DATABASE TO STORE STATE BETWEEN
EACH METHOD CALL FROM THE CLIENT
ARE MORE OF A PERFORMANCE HIT
THAN THE LESS SCALABLE NATURE OF
STATEFUL SESSION BEANS
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 16
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 17
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 18
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 19
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(OW DOES THE CLIENT KNOW WHICH METHODS TO CALL
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 20
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 21
(-%DUFKLWHFWXUH
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This sharpen gets you on the one most common
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 22
DUFKLWHFWXUDORYHUYLHZ
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)N %*" A CLIENTS ENTRY POINT INTO THE
ENTERPRISE APPLICATION IS NEARLY ALWAYS
THROUGH A REFERENCE STUB TO A 2EMOTE
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NECESSARY TO USE A LOCAL CLIENT IE A
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WHICH DOESNT USE 2-) TO INVOKE BUSINESS
METHODS BUT THIS IS FOR ONLY A FEW VERY
SPECIAL CASES
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 23
(-%REMHFW
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BEANS BODYGUARD 4HE BEAN SITS BACK PROTECTED FROM ALL
CLIENT INVOCATIONS WHILE THE %*"/BJECT IMPLEMENTS THE
2EMOTE INTERFACE AND TAKES THE REMOTE CALLS /NCE THE CALL
GETS TO THE %*"/BJECT THE SERVER JUMPS IN WITH ALL THE SERVICES
LIKE SECURITY IS THIS CLIENT AUTHORIZED TO CALL THIS METHOD
TRANSACTIONS IS THIS CALL PART OF AN EXISTING TRANSACTION OR
SHOULD WE START ANOTHER TRANSACTION AND PERSISTENCE DOES
THE BEAN NEED TO LOAD INFO FROM THE DATABASE BEFORE RUNNING
THE CLIENTS METHOD 4HE %*"/BJECT IMPLEMENTS THE 2EMOTE BUSINESS INTERFACE SO
THE REMOTE CALLS FROM THE CLIENT COME TO THE %*"/BJECT "UT
ITS STILL THE BEAN THAT HAS THE REAL BUSINESS LOGIC EVEN THOUGH
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 24
DUFKLWHFWXUDORYHUYLHZ
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)N %*" THE BUSINESS INTERFACE IS CALLED THE COMPONENT
INTERFACE 4HIS IS WHERE YOU EXPOSE YOUR BUSINESS
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 25
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ookCCaarrttBBeeaann does
not implement the
ookCart interfa
ce!
ut it sure looks lik
e it does...)
The bean developer must make sure that
h the
the bean class has methods that matcexact
methods in the component interface,the ly
as if the bean class DID implement
component interface.
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 26
DUFKLWHFWXUDORYHUYLHZ
WKHUH DUH QR
'XPE 4XHVWLRQV
Q:
) JUST WANT TO BE SURE )M CLEAR ABOUT THIS
INTERFACES CAN %84%.$ OTHER INTERFACES
A:
9ES INTERFACES HAVE THEIR OWN INHERITANCE TREE
)N FACT WITH INTERFACES YOU CAN DO SOMETHING YOU
CANT EVER DO WITH A CLASSˆAN INTERFACE CAN EXTEND
MORE THAN ONE INTERFACE
LQWHUIDFH&DUWH[WHQGV(-%2EMHFW&DUW%XVLQHVV
Q:
"UT WHAT DOES THAT REALLY MEAN WHEN AN
INTERFACE EXTENDS ANOTHER INTERFACE %XTENDING
MEANS INHERITANCE BUT WHAT IS THE INTERFACE
INHERITING
A:
7HEN ONE INTERFACE EXTENDS ANOTHER IT
INHERITS EVERYTHING FROM THAT INTERFACE 7HOEVER
IMPLEMENTS AN INTERFACE MUST IMPLEMENT NOT JUST THE
METHODS FROM THAT INTERFACE BUT ALSO THE METHODS
FROM EVERY INTERFACE THAT INTERFACE EXTENDS ALL THE
WAY UP THE INTERFACE INHERITANCE TREE
3O IN THIS EXAMPLE WHOEVER IMPLEMENTS "OOK#ART
MUST ALSO IMPLEMENT THE METHODS OF %*"/BJECT
:KHQ\RXLPSOHPHQW
DQLQWHUIDFH\RXPXVW
LPSOHPHQWDOOWKH
PHWKRGVWKDWLQWHUIDFH
LQKHULWVIURPLWVVXSHU
LQWHUIDFHV
6RZKRHYHULPSOHPHQWV
%RRN&DUWPXVWLPSOHPHQW
WKHPHWKRGVIURPERWK
%RRN&DUWDQG(-%2EMHFW
Q:
7HY DOESNT THE BEAN IMPLEMENT THE
2EMOTEBUSINESS INTERFACE )SNT THE WHOLE
POINT OF AN INTERFACE IMPLEMENTATION TO USE THE
COMPILER TO KEEP YOU HONEST AND TO SUPPORT *AVA
TYPE CHECKING
A:
9OU ASKED THIS QUESTION BEFORE "UT HEY
WE ALL FORGET THINGS SO WELL REMIND YOU AGAIN 4HE
BEAN DOESNT IMPLEMENT THE 2EMOTE INTERFACE
BECAUSE THE BEAN IS NEVER SUPPOSED TO BE A
2EMOTE OBJECT IN THE *AVA 2-) SENSE )N OTHER
WORDS YOU NEVER EVER WANT ANYONE TO HAVE A STUB
TO THE ACTUAL BEAN )F YOU WERE TO SOMEHOW SNEAK
A REMOTE REFERENCE IE A STUB OUT TO THE WORLD
YOUD BE DEFEATING THE WHOLE PURPOSE OF %*" )F YOU
LET A CLIENT TALK DIRECTLY TO THE BEAN THEN THE SERVER
WOULDNT BE ABLE TO APPLY ITS SERVICES AND IF YOU
DONT NEED THE SERVICES YOU SEE WHERE WERE GOING
HERE
4ECHNICALLY IT IS LEGAL TO HAVE THE BEAN IMPLEMENT
THE 2EMOTE INTERFACE BUT ITS A REALLY BAD IDEA SINCE
YOU COULD MAKE MISTAKES THAT WOULDNT BE CAUGHT
AT COMPILE TIME BUT WHICH WOULD BLOW UP LATER "UT YOU DONT NEED TO DO IT SINCE VIRTUALLY ALL BEAN
DEVELOPMENT TOOLS INCLUDING NEARLY EVERY BEAN
AWARE )$% UNDERSTAND THE RELATIONSHIP BETWEEN
THE BEAN THE %*"/BJECT AND THE 2EMOTE INTERFACE
AND THEY GUARANTEE THAT THE COMPONENT INTERFACE
AND THE BEAN CLASS HAVE MATCHING METHODS
Q:
"UT WHAT IF ) JUST lND THIS TOO DISTURBING
4HIS WHOLE IDEA VIOLATES MY *AVA SENSIBILITIES THE
VERY PRINCIPLES UPON WHICH ) CODE 3URELY THERE
MUST BE SOMETHING ) CAN DO
A:
9OU COULD TRUST US ON THE WHOLE hYOURE
ALMOST CERTAINLY USING TOOLS SO IT REALLY WONT
MATTER 2EALLYv THING BUT NO SO IF YOU INSIST YES
THERE IS SOMETHING YOU CAN DO THATLL PROBABLY HELP
YOU FEEL BETTER )TS ON THE NEXT PAGE BUT YOU CAN
PROBABLY FIGURE IT OUT YOURSELF ANYWAY
.ONETHELESS WERE STICKING BY OUR STORY THAT MOST
DEVELOPERS WONT NEED TO DO THIS
\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 27
LQWHUIDFHLPSOHPHQWDWLRQ
$GHVLJQIRUWKRVHZKRIHHO
VTXHDPLVKWKDWWKHEHDQ
GRHVQ·WLPSOHPHQWWKH
EXVLQHVVPHWKRGLQWHUIDFH
LQWHUIDFH!!
5HPRWH
Create an int
the business meerthfaodce that has
not extend EJBObjs, but does
ect (so itÕs
not a remote int
erface).
LQWHUIDFH!!
(QWHUSULVH%HDQ
QRPHWKRGV
QRPHWKRGV
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rface
ponent inBtOebject
m
o
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t
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th the EJ
extends boAND the business
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interf interface.
method
Make the bean class lem
ent
both the SessionBeanimp
interface
AND the business metho
d
interface. Now, the compile
r will
make sure you have the
right
methods in the bean class.
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 28
DUFKLWHFWXUDORYHUYLHZ
6R,ZULWHP\EHDQDQG
,SXWLQPDWFKLQJPHWKRGV
IURPWKHFRPSRQHQWLQWHUIDFH
ZLWKRXWRIÀFLDOO\LPSOHPHQWLQJ
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LQWHUIDFHZKRGRHV"
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QUXTMUMV\\PMKWUXWVMV\QV\MZNIKM'
1VW\PMZ_WZL[_PWUISM[\PM
-2*7JRMK\KTI[['
4HE CONTAINER 9OU DECLARE THE METHODS BUT THE CONTAINER
IMPLEMENTS YOUR COMPONENT INTERFACE 2EMEMBER YOUR
COMPONENT INTERFACE IS THE ONE THAT EXTENDS %*"/BJECT SO THE
CONTAINER HAS TO IMPLEMENT NOT JUST YOUR BUSINESS METHODS BUT
ALSO THE METHODS OF %*"/BJECT WHICH WE HAVENT YET LOOKED AT Q:
"UT HOW DOES THE CONTAINER KNOW WHAT TO PUT IN THOSE
METHODS )M THE ONE WHO DECLARED THOSE METHODS
A:
2EMEMBER THE CONTAINER ISNT IMPLEMENTING THE REAL BUSINESS
LOGIC 4HE TRUE FUNCTIONALITY FOR THOSE BUSINESS METHODS LIVES IN YOUR
BEAN CLASSˆTHE CLASS THAT YOU IMPLEMENT 4HE CLASS IMPLEMENTING THE
COMPONENT INTERFACE IS GOING TO BE THE %*"/BJECT 4HE BODYGUARD 4HE
2EMOTE OBJECT !ND REMEMBER THAT THE %*"/BJECT IS ONLY PRETENDING
TO BE THE BEAN )T CAN RESPOND TO THE REMOTE METHOD CALLS COMING FROM
THE CLIENT VIA THE STUB BUT THE %*"/BJECTS ONLY JOB IS TO CAPTURE THE
INCOMING CLIENT CALLS TO THE BEAN !FTER THAT ITS UP TO THE CONTAINER
SERVER TO TAKE OVER
7E DONT REALLY KNOW HOW THE %*"/BJECT IS IMPLEMENTEDˆITS
COMPLETELY UP TO THE VENDOR "UT WE DONT REALLY CARE !LL YOU NEED TO
KNOW IS THAT AN %*" CONTAINER IS REQUIRED BY THE SPEC TO GENERATE THE
CODE FOR THE %*"/BJECT AND ITS CORRESPONDING STUB \RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 29
ZKRFUHDWHVZKLFKFODVV
?PWKZMI\M[_PI\'
&OR A BEAN WITH A REMOTE CLIENT VIEW IN OTHER WORDS A BEAN THAT CAN BE ACCESSED
BY REMOTE CLIENTS YOU KNOW THAT YOU HAVE TO WRITE THE #OMPONENT INTERFACE AND
THE "EAN CLASS "UT SOMEBODY HAS TO WRITE THE CLASS THAT IMPLEMENTS YOUR #OMPONENT
INTERFACE TO MAKE THE 2EMOTE %*"/BJECT AND SOMEBODY HAS TO MAKE THE STUB THAT
GOES WITH THAT %*"/BJECT 4HAT SOMEBODY IS THE #ONTAINER !ND THOUGH WE HAVENT YET
TALKED ABOUT THE (OME WEVE LISTED THE RELEVANT PIECES HERE FOR COMPLETENESS
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 30
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 31
(-%DUFKLWHFWXUH
there are no
Dumb Questions
Q:
(OW AND WHEN DOES THE
CONTAINER CREATE THE %*"/BJECT AND
THE (OME AND THE STUBS
A:
7HEN YOU DEPLOY A BEAN
THE CONTAINER LOOKS AT THE $$ AND
TAKES IT FROM THERE 2EMEMBER THE
$$ GIVES THE FULLY QUALIFIED NAME OF
YOUR 2EMOTE #OMPONENT %*"/BJECT
INTERFACE AND YOUR 2EMOTE (OME
INTERFACE 3O ONCE THE CONTAINER GETS
THOSE INTERFACES IT GENERATES CODE
FOR THE TWO CLASSES IMPLEMENTING
THOSE INTERFACES !ND BECAUSE THEYRE
2EMOTE THE CONTAINER ALSO CREATES
THE CLIENT STUBS THAT KNOW HOW TO
COMMUNICATE BACK TO THE 2EMOTE
OBJECTS
Q:
!RE THESE ALWAYS PLAIN OLD 2-)
STUBS ) SEE THAT WHEN WE DEPLOYED
USING THE 2) IT PRINTED OUT A MESSAGE
THAT IT WAS RUNNING RMIC
A:
4HE CONTAINER CAN DO WHAT
EVER IT WANTS TO CREATE THE STUBS THE
REQUIREMENT IS THAT THE STUBS BE 2-)
))/0 COMPLIANT )N FACT A SERVER CAN
USE SOMETHING CALLED DYNAMIC PROXIES
TO IMPLEMENT THE STUB FUNCTIONAL
ITY BUT WE DONT CARE 7HEN WE SAY
hSTUBv WE MEAN SOMETHING WITH STUB
BEHAVIOR 7HETHER ITS AN 2-) STUB OR
SOMETHING ELSE IS AN IMPLEMENTATION
DETAIL FOR THE SERVER 7ELL LOOK AT THAT
IN MORE DETAIL IN THE NEXT CHAPTER 4HE
BOTTOM LINE IS THAT YOU REALLY DONT
KNOW WHAT THE STUB CLASS CODE LOOKS
LIKE &OR THAT MATTER YOU REALLY DONT
KNOW HOW THE %*"/BJECT AND THE
(OME ARE IMPLEMENTED 9OURE NOT
SUPPOSED TO KNOW
9OU MIGHT HAVE AN %*" CONTAINER THAT
LETS YOU VIEW POSSIBLY EVEN HACK
THE GENERATED SOURCE CODE BUT DONT
COUNT ON IT !ND IF WE WERE YOU WE
JUST WOULDNT GO THERE EVEN IF WE
COULD
Q:
3O THESE CLASSES ARE UP TO THE
VENDORS IMPLEMENTATION
A:
9ES 4HE VENDOR HAS ALL SORTS
OF CHOICES FOR IMPLEMENTING THESE
CLASSES AND MIGHT USE THE STUBS AND
OR (OME AND %*"/BJECTS TO GET SOME
PERFORMANCE ADVANTAGES "UT AGAIN
THATS NOT UP FOR YOU TO MESS WITH OR
EVEN KNOW ABOUT
4HE ONLY REQUIREMENT IN THE SPEC
THAT YOURE GUARANTEED AND REQUIRED
TO ADHERE TO IS THAT 2EMOTE OBJECTS
MUST FOLLOW THE RULES FOR 2-) ))/0
WHICH MEANS *AVAS 2EMOTE -ETHOD
)NVOCATION USING THE ))/0 #/2"!
STANDARD WIRE PROTOCOL
Q:
9OU BROUGHT IT UP HOW IS 2-)
))/0 DIFFERENT FROM REGULAR 2-)
A:
0LAIN OLD 2-) USES *2-0 AS ITS
WIRE PROTOCOL "UT ))/0 LETS 2EMOTE
OBJECTS INTEROPERATE THROUGH #/2"!
WE WONT BE SAYING MUCH AT ALL ABOUT
#/2"! IN THIS BOOK ITS DEFINITELY OUT
OF SCOPE FOR THE EXAM AND THE BOOK
EXCEPT IN A FEW TINY CASES WELL SEE
SCATTERED THROUGHOUT THE CHAPTERS 4HAT GIVES YOUR OBJECTS A CHANCE TO BE
ACCESSED FOR EXAMPLE BY EVEN NON
*AVA CLIENTS /NE THING ))/0 SPECIFIES IS
THE WAY INFORMATION FOR TRANSACTIONS
AND SECURITY CAN BE PROPAGATED
ALONG WITH THE METHOD CALL AND YOUR
CONTAINER MIGHT BE TAKING ADVANTAGE
OF THAT
&OR THE MOST PART YOULL BARELY NOTICE
THE DIFFERENCE BETWEEN PLAIN OLD 2-)
AND 2-) ))/0 "UT THERE ARE A COUPLE
OF PLACES WHERE ITS DIFFERENT AND ONE
OF THESE DIFFERENCES IS DEFINITELY ON
THE EXAMˆTHE NEED TO NARROW A STUB
7ELL COVER NARROWING IN DETAIL IN THE
NEXT CHAPTER ON #LIENT 6IEW &OR NOW
JUST KNOW THAT ITS SOMETHING A CLIENT
MUST DO WITH AN %*" STUB THAT THEY
DONT HAVE TO DO WITH A PLAIN *AVA
STUB BECAUSE THE %*" SPEC TELLS YOU TO
ASSUME THAT THE STUB IS USING ))/0 AND
THUS MIGHT BE A DIFFERENT KIND OF STUB
Q:
7HEN ARE WE GOING TO TALK
ABOUT THE (OME
A:
Q:
.EXT PAGE
7HY DID YOU TAKE SO LONG
)SNT THE (OME IMPORTANT
A:
!S CRUCIAL AS THE (OME IS
ITS USUALLY JUST THE WAY YOU GET
A REFERENCE TO SOMETHING THAT
IMPLEMENTS THE #OMPONENT INTERFACE
)N OTHER WORDS YOU USE THE (OME TO
GET AN %*"/BJECT STUB FOR 2EMOTE
CLIENTS WHICH IS ALL WEVE TALKED ABOUT
SO FAR &OR %NTITY BEANS THE (OME CAN HAVE
A MORE IMPORTANT ROLE AND WELL SEE
THAT BUT EVEN WITH %NTITY BEANS THE
(OMES PRIMARY USE IS STILL TO GET
%*"/BJECT STUBS !FTER THAT MOST OF
THE COMMUNICATION BETWEEN THE
CLIENT AND THE BEAN COMES THROUGH
THE %*"/BJECT AND NOT THE (OME
-OST OF THE TIME IN FACT CLIENTS USE
THE (OME JUST TO GET THE %*"/BJECT
REFERENCE AND THEN THE (OME
REFERENCE IS TOSSED OUT NOT NEEDED
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Page 32
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 33
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 35
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 37
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 39
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&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 40
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 41
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&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 42
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The bean stays in the bean pool ! It comes out only to service an actual
business method, if the client invokes one on the EJBObject stub.
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\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 43
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&IRST WE HAVE TO DElNE WHAT CREATE MEANS &OR A SESSION BEAN IT
MEANS THE BEAN INSTANCE IS PHYSICALLY INSTANTIATED AND INITIALIZED
AS A BEAN &OR AN ENTITY BEAN ITS COMPLETELY DIFFERENT SO THIS
CONVERSATION APPLIES JUST TO SESSION BEANS ,ATER WELL GET INTO
WHAT IT MEANS TO CREATE AN ENTITY BEAN
&OR STATEFUL SESSION BEANS THE CREATE IS TRIGGERED BY THE CLIENT
4HE CLIENT CALLS CREATE ON A (OME STUB AND EVERYTHING HAPPENS
AT THAT POINTˆAN %*"/BJECT IS INSTANTIATED FOR THIS NEW ABOUT TO
BE CREATED BEAN AND THEN THE BEAN ITSELF IS CREATED AND LINKED TO
THE %*"/BJECT THE BEANS BODYGUARD "UT FOR STATELESS SESSION BEANS THE CLIENT CREATE AND THE ACTUAL
CREATION OF THE BEAN ARE DECOUPLED )N OTHER WORDS JUST BECAUSE
THE CLIENT CALLS CREATE ON A (OME STUB DOESNT MEAN A BEAN WILL
BE CREATED AT THAT POINT
3TATELESS SESSION BEANS ARENT CREATED UNTIL THE CONTAINER DECIDES
IT NEEDS ONE AND THATS REALLY UP TO THE CONTAINER )T MIGHT
FOR EXAMPLE MAKE A BUNCH OF BEAN INSTANCES IE CREATE SOME
BEANS AND PLOP THEM IN A POOL BEFORE EVEN A SINGLE CLIENT
HAS ASKED FOR ONE BY CALLING CREATE ON A (OME STUB /R THE
CONTAINER MIGHT MAKE JUST IN TIME BEANS AND WAIT UNTIL THE
CLIENT INVOKES A BUSINESS METHOD BEFORE GOING TO THE TROUBLE OF
PHYSICALLY CREATING THE BEAN
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 44
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The bean comes out of the pool
ONLY when a client invokes
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EJBObject stub. So, a single
bean can jump out to handle
one clientÕs call, then jump back
in the pool, then jump out to
handle a different clientÕs call,
and then jump back in the pool...
\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 45
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(ERES SOMETHING THAT IS 2%!,,9
STARTING TO ANNOY ME WHY DO YOU HAVE A
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WHEN THE 2EMOTE OBJECTS ARE CALLED THE
(OME AND THE %*"/BJECT 7HY ISNT IT JUST
THE %*"/BJECT INTERFACE AND THE (OME/BJECT
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YOULL GET USED TO IT "E THANKFUL IT WAS EVEN
WORSE IF YOU LEARNED %*" PRIOR TO VERSION WHEN IT WAS CALLED THE (OME AND THE 2EMOTE
.OW THAT WAS A REAL PROBLEM BECAUSE FIRST
OF ALL BOTH THE (OME AND THE 2EMOTE WERE
2EMOTE IN THE JAVARMI SENSE 3ECOND AS OF
%*" YOU CAN HAVE A (OME AND A 2EMOTE
THAT ARENT ACTUALLY 2EMOTE 3O THEY HAD
TO CHANGE THE NAME TO #OMPONENT INTERFACE
INSTEAD OF CALLING IT 4(% 2EMOTE INTERFACE
SINCE IT MIGHT IN FACT NOT BE 2EMOTE )F YOU
JUST REMEMBER THAT THE #OMPONENT INTERFACE
IS WHERE THE BUSINESS METHODS ARE AND THE
(OME IS WHERE THE UM (OME METHODS ARE
YOU SHOULD BE FINE *UST REMEMBER #OMPONENT
BUSINESS %*"/BJECT OR %*",OCAL/BJECT BUT
WE WONT GO THERE UNTIL THE NEXT CHAPTER 7)
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
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Page 46
DUFKLWHFWXUDORYHUYLHZ
there are no
Dumb Questions
Q:
(OW DOES THIS WORK )S THERE
ONE BEAN POOL FOR ALL BEANS OR ONE
BEAN POOL FOR A PARTICULAR TYPE OF
BEAN
A:
)N REALITY WE DONT KNOW WHAT
THE CONTAINER IMPLEMENTATION IS BUT
CONCEPTUALLY THERES ONE POOL FOR
EVERY BEAN TYPE 3O IF YOU DEPLOY
AN !DVICE"EAN AND A 7EATHER"EAN
AND BOTH ARE STATELESS SESSION BEANS
THEYLL EACH GET THEIR OWN POOL
Q:
$OES EACH STATELESS SESSION
BEAN HAVE ITS OWN %*"/BJECT
A:
3ORT OF ! STATELESS SESSION
BEAN DOESNT NEED A BODYGUARD
UNTIL HES ACTUALLY INVOLVED IN A
METHOD INVOCATION 3O THE CLIENT
GETS A REFERENCE TO AN %*"/BJECT
BUT THE BEAN ISNT ASSOCIATED WITH
THAT %*"/BJECT UNTIL THE CLIENT CALLS
A BUSINESS METHOD !T THAT POINT
THE BEAN SLIDES OUT OF THE POOL TO
SERVICE THE METHOD 3O THE %*"/BJECT
THE CLIENT HAS IS FOR A KIND OF BEAN
!DVICE"EAN 7EATHER"EAN ETC BUT
NOT A SPECIFIC INSTANCE OF A BEAN
Q:
7HY DONT STATEFUL SESSION
BEANS HAVE A POOL
A:
(AVE YOU ALREADY THOUGHT
ABOUT THIS IN THE "RAIN 0OWER ON THE
PREVIOUS PAGE "ECAUSE IF YOU HAVENT
DONT READ ANY FURTHER UNTIL YOUVE
COME UP WITH YOUR OWN IDEAS )F YOU
MADE IT THIS FAR WE ASSUME THAT YOU
ALREADY KNOW THE ANSWER AND WERE
JUST CONFIRMING IT
! STATEFUL BEAN REMEMBER HOLDS CLIENT
CONVERSATIONAL STATE 4HAT MEANS THE
BEAN HAS TO SAVE CLIENT SPECIFIC STATE
IN OTHER WORDS IT HAS TO REMEMBER
THINGS ABOUT THIS CLIENT ACROSS
MULTIPLE METHOD INVOCATIONS FROM THE
CLIENT
4HINK OF A SHOPPING CART AGAINˆA
STATEFUL BEAN NEEDS TO REMEMBER
WHATS IN THE CLIENTS CART EACH TIME THE
CLIENT CALLS ADD)TEM4O#ART ! STATELESS
BEAN ON THE OTHER HAND DOESNT HAVE
TO REMEMBER ANYTHING ON THE CLIENTS
BEHALF SO TO A CLIENT ONE STATELESS
BEAN OF A PARTICULAR TYPE IS AS GOOD
AS ANY OTHER BEAN OF THAT TYPE
)F THE !DVICE"EAN SIMPLY RETURNS
A PIECE OF ADVICE NOT CONNECTED
IN ANY WAY TO ANYTHING IT TOLD THE
CLIENT BEFORE OR ANYTHING THE CLIENT
TOLD IT THEN THERES NO NEED FOR THE
!DVICE"EAN TO BE STATEFUL )N THAT CASE
EACH TIME A CLIENT CALLS GET!DVICE
ON THE #OMPONENT INTERFACE IE THE
%*"/BJECT ANY !DVICE"EAN IS JUST AS
CAPABLE OF RUNNING THE METHOD AS ANY
OTHER
/N THE OTHER HAND IF THE !DVICE"EAN
WERE MODIFIED TO RETURN SAY RANDOM
BUT NON REPEATING ADVICE THEN THE
!DVICE"EAN WOULD HAVE TO BE STATEFUL
SO THAT IT COULD KEEP TRACK OF PREVIOUS
ADVICE AND NEVER REPEAT IT
Q:
(OW LONG DOES A STATEFUL BEAN
KEEP CLIENT SPECIlC STATE
A:
/NLY FOR THE LIFE OF THE SESSION
! SESSION CONTINUES UNTIL THE CLIENT
TELLS THE BEAN HES DONE BY CALLING
REMOVE ON THE BEANS #OMPONENT
INTERFACE OR THE SERVER CRASHES OR THE
BEAN TIMES OUT WELL COVER THAT IN THE
3ESSION LIFECYCLE CHAPTER Q:
3O STATEFUL SESSION BEANS
ARENT SCALABLE
A:
.O THEY ARE *UST NOT AS SCALABLE
AS STATELESS BEANS
Q:
(OW CAN A STATEFUL BEAN BE
SCALABLE IF YOU ALWAYS NEED ONE BEAN
FOR EVERY CLIENT
A:
9OU DO NEED A SEPARATE BEAN
ALLOCATED FOR EACH CLIENT BUT NOT EVERY
BEAN HAS TO BE ACTIVELY CONSUMING
RESOURCES )F THE STATEFUL SESSION BEAN
CLIENT IS TAKING A LONG TIME BETWEEN
METHOD CALLS THE STATEFUL BEAN CAN
BE TEMPORARILY TAKEN DOWN AND PUT
IN A STATE CALLED PASSIVATION 4HIS STATE
PRESERVES THE CLIENT SPECIFIC STATE OF
COURSE BUT REDUCES THE NUMBER OF
BEANS CURRENTLY ALIVE IN THE SERVER 4HE
BEAN COMES OUT OF PASSIVATION AND
BACK INTO ACTIVE DUTY ACTIVATION WHEN
THE CLIENT CALLS A BUSINESS METHOD
\RXDUHKHUH
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
Return to Table of Contents
Page 47
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The client sends a message to a JMS messaging service.
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onMessage() MessageListener interface method).
&KDSWHU
Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 48
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 2. EJB Architecture
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Page 49
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 2. EJB Architecture
Return to Table of Contents
Page 50
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 51
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Chapter 2. EJB Architecture
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Table of Contents
Chapter 3. Exposing Yourself...................................................................... 1
Section 3.1. Objectives..................................................................................................................................................................... 2
Section 3.2. What the client really wants........................................................................................................................................ 3
Section 3.3. It all starts with the home interface............................................................................................................................ 4
Section 3.4. There are no Dumb Questions.................................................................................................................................... 4
Section 3.5. How a client uses a session bean: create, use, and remove........................................................................................ 5
Section 3.6. But first, we have to get a home interface reference.................................................................................................. 6
Section 3.7. What's JNDI?.............................................................................................................................................................. 6
Section 3.8. Getting the home interface stub................................................................................................................................. 7
Section 3.9. There are no Dumb Questions.................................................................................................................................... 8
Section 3.10. Let's take another look at the complete client code.................................................................................................. 9
Section 3.11. Sharpen your pencil................................................................................................................................................... 9
Section 3.12. Just when you thought a simple cast would be enough.......................................................................................... 10
Section 3.13. But NO. You have to narrow the object as well!...................................................................................................... 10
Section 3.14. OK, I'll bite. Why can't you just do a plain old cast ?.............................................................................................. 10
Section 3.15. PortableRemoteObject.narrow().............................................................................................................................. 11
Section 3.16. Think of narrowing as "Exotic Casting".................................................................................................................. 12
Section 3.17. Now that we (finally) have the home stub, let's use it to get what we REALLY want............................................ 13
Section 3.18. There are no Dumb Questions................................................................................................................................. 14
Section 3.19. Writing the Remote home interface for a session bean.......................................................................................... 15
Section 3.20. Remote home interface examples for session beans.............................................................................................. 16
Section 3.21. If you're a client, and you want to........................................................................................................................... 19
Section 3.22. Sharpen your pencil................................................................................................................................................ 22
Section 3.23. But enough about the home... let's talk about the EJB object. The component interface. The thing you REALLY
want............................................................................................................................................................................................... 23
Section 3.24. Imagine what else you might want to do with your EJB object reference............................................................. 25
Section 3.25. Online shopping should not be rushed.................................................................................................................. 28
Section 3.26. Thankfully, we've got handles................................................................................................................................. 29
Section 3.27. isIdentical ?: how to find out if two stubs refer to the same bean.......................................................................... 31
Section 3.28. There are no Dumb Questions................................................................................................................................ 33
Section 3.29. A bean's client interfaces can be local .................................................................................................................... 35
Section 3.30. BRAIN POWER....................................................................................................................................................... 35
Section 3.31. Sharpen your pencil................................................................................................................................................. 37
Section 3.32. Which methods make sense for the local client interfaces?.................................................................................. 38
Section 3.33. When you think handle , think Remote.................................................................................................................. 39
Section 3.34. Who needs EJBMetaData when you've got reflection?.......................................................................................... 39
Section 3.35. Do you need isIdentical() when there's equals() ?................................................................................................. 40
Section 3.36. Why so many remove methods?............................................................................................................................. 41
Section 3.37. How can you use a remove that takes a handle when you don't have a handle?................................................... 43
Section 3.38. There are no Dumb Questions................................................................................................................................ 43
Section 3.39. Comparing Remote vs. Local interfaces................................................................................................................. 44
Section 3.40. Sharpen your pencil................................................................................................................................................ 45
Section 3.41. Writing the local client interfaces........................................................................................................................... 46
Section 3.42. You can have both a Remote and local client view for a bean, but you probabl won't.......................................... 47
Section 3.43. Sharpen your pencil................................................................................................................................................ 48
Section 3.44. Exceptions in client interfaces: what the client might get..................................................................................... 49
Section 3.45. Local client code...................................................................................................................................................... 50
Section 3.46. BRAIN POWER: What has to change inside the bean class?................................................................................. 51
Section 3.47. Arguments to Remote vs. local methods................................................................................................................ 53
Section 3.48. There are no Dumb Questions................................................................................................................................ 54
Section 3.49. Exercise: BE the Container..................................................................................................................................... 55
Section 3.50. Exercise Solutions: BE the Container..................................................................................................................... 57
Section 3.51. COFFEE CRAM....................................................................................................................................................... 58
Section 3.52. COFFEE CRAM....................................................................................................................................................... 60
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 1
the client view
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 2
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 3
WKHFOLHQWYLHZ
?PI\\PMKTQMV\ZMITTa_IV\[
4HE CLIENT HAS A GOAL ! VISION ! QUEST 3HE WANTS TO CALL A BUSINESS METHOD ON THE
BEAN 3OMETHING EXPOSED IN THE COMPONENT INTERFACE .EVER FORGET THAT ULTIMATE
GOAL IT IS EASY TO GET BOGGED DOWN IN ALL THE DETAILS "UT IF YOU KEEP FOCUSED ON THE
CLIENTS DRIVING NEED YOULL HAVE A MUCH EASIER TIME REMEMBERING THINGS LIKE SAY
THE RETURN TYPE OF A SESSION BEANS HOME CREATE METHOD
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 4
Return to Table of Contents
WKH+RPHLQWHUIDFH
1\ITT[\IZ\[_Q\P\PMPWUMQV\MZNIKM
4HE CLIENT WANTS THE BEAN 7ELL TOO BAD 4HE
CLIENT WILL NEVER GET THE BEAN BECAUSE NOBODY
TALKS TO THE BEAN EXCEPT THE CONTAINER 4HE BEST THE CLIENT CAN HOPE FOR IS A
REFERENCE TO THE BEANS BODYGUARDˆTHE
COMPONENT INTERFACE !ND THE CLIENT
GETS A REFERENCE TO THE BEANS COMPONENT
INTERFACE BY CALLING A METHOD ON THE
BEANS HOME INTERFACE
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REFERENCE AN INTERFACE 4HE REFERENCE VARIABLE CAN BE DECLARED
AS AN INTERFACE TYPE BUT THATS NOT THE SAME THING
A:
7ELL ACTUALLY IT IS THE SAME THING )N THIS BOOK AND IN THE
SPEC AND IN THE EXAM EVERYWHERE YOU SEE THE PHRASE hREFERENCE
TO AN INTERFACEv DO A MENTAL SEARCH AND REPLACE TO MAKE IT
hREFERENCE TO AN OBJECT THAT IMPLEMENTS THE INTERFACEv
)T CAN FEEL A LITTLE STRANGE IF YOU HAVENT READ DOCUMENTS THAT USE
THIS CONVENTION BUT YOU BETTER GET USED TO IT "UT DONT WORRY BY
#HAPTER YOULL WONDER HOW ANYONE EVER SAID IT DIFFERENTLY
Q:
9OU SAID THE CLIENTS ULTIMATE GOAL IS TO CALL METHODS ON
THE BEAN /+ THE COMPONENT INTERFACE BUT YOU KNOW WHAT )
MEAN "UT WITH ENTITY BEANS YOU CAN HAVE BUSINESS METHODS
IN THE HOME RIGHT 3O WITH ENTITY BEANS ISNT IT TRUE THAT
SOMETIMES THE CLIENTS GOAL IS *534 TO USE THE HOME
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9ES YOURE RIGHT 4HEYRE CALLED hHOME BUSINESS METHODSv
AS OPPOSED TO PLAIN OLD hHOME METHODSv OR PLAIN OLD hBUSINESS
METHODSv "UT THEYRE A SPECIAL CASE WELL LOOK AT LATER IN THE
BOOK 4HERE ARE OTHER REASONS TOO FOR WHY YOU MIGHT NEED ONLY
THE HOME OF AN ENTITY BEAN &OR EXAMPLE IF YOU WANT TO CREATE A
BUNCH OF NEW CUSTOMERS IN A DATABASE BUT YOU DONT WANT TO DO
ANY OTHER OPERATIONS ON REFERENCES TO THOSE ENTITY CUSTOMERS
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 5
WKHFOLHQWYLHZ
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\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 6
XVLQJ-1',WRJHWWKHKRPH
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7HEN YOU THE CLIENT WANT A REFERENCE TO A HOME INTERFACE YOU GO THROUGH
*.$) 4HE PROCESS IS PRETTY STRAIGHTFORWARD YOU GIVE *.$) A LOGICAL NAME
THE NAME THE DEPLOYER TOLD THE SERVER TO USE AND YOU GET BACK SOMETHING
THAT IMPLEMENTS THE HOME INTERFACE
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PUT THINGS INTO IT
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SERVICE HAS A *.$) DRIVER CALLED A
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 7
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 8
WKH+RPHLQWHUIDFH
WKHUH DUH QR
'XPE 4XHVWLRQV
Q:
(OW DO ) KNOW WHAT THE
DEVELOPER NAMED THE BEAN
A:
!CTUALLY ITS NOT UP TO THE BEAN
DEVELOPER THE %*" ROLE KNOWN AS "EAN
0ROVIDERˆTHE ONE WHO ACTUALLY WROTE
THE BEAN CODE TO GIVE THE BEAN
ITS *.$) NAME 2EMEMBER THE "EAN
0ROVIDER MIGHT HAVE WRITTEN THAT BEAN
AS A REUSABLE COMPONENT FOR "EANS @2
5S AND THUS MIGHT HAVE NO IDEA WHERE
AND HOW THE BEAN WILL BE USED
)TS THE DEPLOYERˆTHE PERSON WHO
ACTUALLY GETS THE BEAN RUNNING IN THE
SERVER AS PART OF SOME APPLICATIONˆ
WHO REGISTERS THE BEAN UNDER A
LOGICAL NAME "UT THE BOTTOM LINE IS
THAT THERES NO STANDARD OR AUTOMATIC
MECHANISM FOR LEARNING THE NAMES
OF REGISTERED BEANS !S A CLIENT
SOMEBODY SOMEHOW HAS TO TELL YOU
THAT SAY THE BEAN WAS REGISTERED AS
h!DVISORv
.OTICE THAT h!DVISORv WHILE DESCRIBING
THE SERVICE IS NOT A 3TRING THAT
CORRESPONDS DIRECTLY TO THE NAMES OF
ANY OF THE OTHER PIECES OF THE BEAN
2EMEMBER THE COMPONENT INTERFACE
WAS !DVICE THE HOME INTERFACE WAS
!DVICE(OME AND THE BEAN ITSELF IS
!DVICE"EAN 4HE NAME h!DVISORv WAS
JUST SOMETHING THE DEPLOYER THOUGHT
HAD A NICE RING TO IT
/F COURSE IN YOUR COMPANY YOU MIGHT
AND PROBABLY WILL HAVE STRICT NAMING
GUIDELINES TO FOLLOW FOR HOW BEANS ARE
REGISTERED WITH *.$) AT DEPLOYMENT
TIME
5NLESS ITS YOUR OWN COMPANY IN
WHICH CASE YOU CAN DO WHATEVER YOU
DARN WELL PLEASE INCLUDING NAMING
EACH BEAN AFTER YOUR FAVORITE ROCK STAR
OR -ATRIX CHARACTER
Q:
) JUST THOUGHT OF AN EVEN
")''%2 PROBLEM HOW THE HECK DO )
KNOW WHERE TO lND THE SERVER !ND
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CODE FOR AN )0 ADDRESS OR 4#0 PORT
NUMBER
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THE SAME PHYSICAL MACHINE AS THE
CLIENT 3O WERE TAKING ADVANTAGE
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 9
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 10
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4HE RETURN VALUE OF THE #ONTEXTLOOKUP METHOD IS TYPE /BJECT 3O WERE
THINKING A SIMPLE CAST SHOULD BE ENOUGH TO FORCE THE OBJECT REFERENCED BY O
BACK TO THE !DVICE(OME IMPLEMENTATION THAT WE KNOW IT REALLY IS
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, but isnÕt.
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.ARROWING FORCES THE OBJECT RETURNED FROM THE *.$) LOOKUP TO BE ABSOLUTELY
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OPERATION GIVES YOU SOMETHING THAT IS CASTABLE
&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 11
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 12
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 13
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 14
Return to Table of Contents
GRQ¶WQDUURZWKH(-%2EMHFW
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&OR EXAMPLE ))/0 CAN PROPAGATE BOTH TRANSACTION AND
SECURITY INFORMATION IMPORTANT THINGS THAT YOU CANT
SEND WITH A NON ))/0 REMOTE METHOD CALL
3O ))/0 LETS A CONTAINER AT LEAST HAVE THE POTENTIAL FOR
INTEROPERATING WITH OTHER SERVERS INCLUDING POSSIBLY
ONE THAT ISNT *AVA BASED
2EMEMBER #/2"! IS A STANDARD THAT AMONG OTHER
THINGS CAN GIVE TWO OBJECTS WRITTEN IN TWO DIFFERENT
LANGUAGES A CHANCE TO INVOKE EACH OTHERS METHODS
4HIS DOES NOT MEAN THAT YOUR SERVER IS NECESSARILY USING
))/0 4HE SPEC SAYS THAT 9/5ˆTHE DEVELOPERˆHAVE TO
ASSUME THE SERVER IS USING ))/0 WHICH MEANS YOU HAVE
TO BE SURE YOUR BEANS ARE ))/0 COMPLIANT WELL TALK
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)F MY SERVER DOESNT USE ))/0 DO ) STILL HAVE TO
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NOTHING MORE THAN A CAST "UTˆAND THIS IS A REALLY HUGE
BUTˆYOUR CLIENT CODE WONT BE VENDOR INDEPENDENT )N
OTHER WORDS YOU WONT HAVE A PORTABLE APP IF YOU DONT
USE NARROW BECAUSE REDEPLOYING THE BEAN ON A SERVER
THAT DOES USE ))/0 WILL BREAK THE CLIENTS
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)S THERE ANY DOWNSIDE TO USING NARROW %SPE
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DO NOTHING METHOD 4HE SPEC SAYS TO ALWAYS NARROW
AND IT WONT HURT YOU IF IT ISNT NEEDED
&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 15
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.OW THAT YOUVE SEEN THE LOOKUP AND CREATE PROCESS FROM THE CLIENTS POINT OF VIEW
WELL SEE WHAT YOU HAVE TO DO TO WRITE A HOME INTERFACE FOR YOUR BEAN &OR SESSION
BEANS THE PROCESS IS VERY EASY )N FACT FOR STATELESS SESSION BEANS ITS LUDICROUSLY
EASYˆYOU JUST DECLARE A SINGLE NO ARG CREATE METHOD
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 16
WKH+RPHLQWHUIDFH
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4HE EXAMPLES ON THIS PAGE ARE ALL LEGAL EXAMPLES OF 2EMOTE HOME INTERFACES
9OULL SEE SOME THAT COULD BE BOTH STATELESS AND STATEFUL AND SOME THAT COULD BE
ONLY STATEFUL BECAUSE THEY HAVE A CREATE METHOD WITH ARGUMENTS 7EVE DROPPED
THE PACKAGE AND IMPORT STATEMENTS TO PUT MORE ON THE PAGE
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 17
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 18
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 19
Return to Table of Contents
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 20
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THE CLIENT INTERACTS WITH AN ENTITY BEAN HOME IS COMPLETELY DIFFERENT FROM THE WAY A
CLIENT USES A SESSION BEAN HOME 9OULL SEE DRAMATIC DIFFERENCES WHEN WE GET TO THE
ENTITY BEAN CHAPTERS
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 21
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 22
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 23
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 24
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 25
Return to Table of Contents
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 26
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 27
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
Page 28
Return to Table of Contents
WKHJHW+DQGOH PHWKRG
9OURE SHOPPING )TS TOUGH
BECAUSE YOU CANT DECIDE WHETHER
YOURE A SPRING OR A SUMMER
9OU DONT WANT TO BE RUSHED BUT
YOUVE ALREADY GOT A BUNCH OF
STUFF IN YOUR CART WHEN YOU REALIZE
YOURE lVE MINUTES LATE FOR WORK
7VTQVM[PWXXQVO[PW]TLVW\JMZ][PML
9OUD LOVE TO CONTINUE WITH YOUR
SHOPPING ONCE YOU GET TO WORK
7HAT DO YOU DO )F IT WERE
!MAZON YOUR SHOPPING CART
WOULD STILL BE THERE WHEN YOU
LOG IN FROM THE 7EB "UT THIS IS A
PROPRIETARY 3WING BASED SHOPPING
CLIENT APP YOURE USING (OW CAN
YOU GET YOUR %*" OBJECT STUB FROM
YOUR HOME MACHINE TO YOUR WORK
MACHINE
9OU COULD TRY SERIALIZING THE STUB
9EAH THAT MIGHT WORK 4HEN
AGAIN IT MIGHT NOT 4HE STUB HAS
A LIVE NETWORK CONNECTION AND
THERES CERTAINLY NO GUARANTEE YOU
CAN GET THAT SAME CONNECTION
TO THE SAME %*" OBJECT AGAIN
!ND SINCE THAT %*" OBJECT IS
THE COMPONENT INTERFACE FOR
YOUR OWN PERSONAL TEMPORARY
SHOPPING CART BEAN YOU NEED
A WAY TO GET BACK TO YOUR EXACT
SAME %*" OBJECT AGAIN FROM WORK
+PPPP\QH[WGRRU
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 29
WKHFOLHQWYLHZ
<PIVSN]TTa_M¼^MOW\PIVLTM[
handle
handle
handle
handle
LQWHUIDFH!!
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no handle
! HANDLE CAN RESCUE YOUR SHOPPING EXPERIENCE !SK
THE BEAN VIA THE %*"/BJECT INTERFACE FOR A HANDLE
+DQGOHP\+DQGOH P\&DUWJHW+DQGOH
SERIALIZE IT EMAIL IT TO YOURSELF THEN DESERIALIZE ON YOUR
WORK MACHINE AND YOURE BACK IN BUSINESS
4HE HANDLE IS A 3ERIALIZABLE THING THAT KNOWS HOW TO
GET BACK TO THE STUB )T HAS A SINGLE METHOD
SXEOLF(-%2EMHFWJHW(-%2EMHFW
3O WHEN YOU CALL IT YOU HAVE TO CAST AND NARROW THE
STUB THAT COMES BACK 2EMEMBER YOU ALWAYS HAVE TO
CAST AND NARROW A STUB UNLESS THE METHOD THAT RETURNS
IT HAS THE ACTUAL 2EMOTE INTERFACE AS ITS DECLARED RETURN
TYPE 3INCE THE HANDLES METHOD HAS NO FRICKIN CLUE
WHAT YOUR COMPONENT INTERFACE IS SAY 3HOPPING#ART
YOURE FACED WITH THE SAME SCENARIO YOU HAD WITH THE
HOME STUB YOU GOT FROM THE *.$) LOOKUP METHOD
#AST AND NARROW #AST AND NARROW #AST AND NARROW
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 30
(-%+DQGOHV
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9OUR SECURITY IS ON A METHOD BY METHOD BASIS SO
EVEN IF YOU GIVE A HANDLE TO SOMEONE ELSE IF THAT
CLIENT DOESNT HAVE AUTHORIZATION TO CALL METHODS
ON THE BEAN THE STUB THEY GET BACK FROM THE
HANDLE WILL BE USELESS
-XVWEHFDXVH\RXVWLOOKDYHDKDQGOHGRHVQ·W
PHDQWKHVHUYHUVWLOOKDV\RXUEHDQ
)F YOURE SHOPPING AND YOU GET A HANDLE AND
THEN THE SERVER DETECTS THAT YOU HAVENT BEEN
DOING ANYTHING WITH YOUR CART FOR A WHILE THE
SERVER CAN TEMPORARILY SAVE YOUR BEAN KNOWN AS
PASSIVATION TO CONSERVE RESOURCES BUT KEEP YOUR
CART AROUND JUST IN CASE YOU COME BACK "UT IF YOU
STILL DONT COME BACK WITHIN SOME TIME PERIOD
THE SERVER WILL DESTROY YOUR CART WITH NO HOPE OF
RESURRECTING IT 4HAT BEAN IS HISTORY
)N THAT CASE YOUR CART WONT BE THERE WHEN YOU
CALL GET%*"/BJECT ON THE HANDLE AND YOULL GET
A 2EMOTE%XCEPTION
&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 31
WKHFOLHQWYLHZ
Q[1LMV\QKIT'
PW_\WNQVLW]\QN\ _W[\]J[
ZMNMZ\W\PM[IUMJMIV
LQWHUIDFH!!
(-%2EMHFW
These twins are
identical if
theyÕre stateLES
can each do the S, since they
clients wonÕt same thing and
But if theyÕreknstow the difference.
they are alway ateFUL, then
twins cannot bes distinct. Stateful
they can hold identical, because
ormation spec
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ique client. iÞc
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)F YOUVE GOT TWO STUBS AND YOU WANT TO KNOW IF THEY REFER
TO THE SAME BEAN YOU CALL IS)DENTICAL ON ONE REFERENCE
PASSING IN THE REFERENCE YOU WANT TO COMPARE IT AGAINST
*UST LIKE THE WAY YOU USE THE EQUALS METHOD
4HE TRICK IS STATELESS SESSION BEANS STATEFUL SESSION BEANS
AND ENTITY BEANS EACH HAVE DIFFERENT RULES FOR WHAT CAUSES
IS)DENTICAL TO RETURN TRUE
6WDWHOHVVVHVVLRQEHDQV
4RUE IF BOTH REFERENCES CAME FROM THE SAME HOME EVEN IF
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4O THE SERVER ONE STATELESS BEAN IS AS GOOD AS ANY OTHER
BEAN FROM THE SAME HOME BECAUSE THE CLIENT WOULD NEVER
BE ABLE TO TELL THE DIFFERENCE SINCE THE BEAN CANT HOLD ANY
CLIENT SPECIlC STATE 6WDWHIXOVHVVLRQEHDQV
&ALSE NO MATTER WHAT FOR ANY TWO UNIQUE STUBS
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\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 32
WKHLV,GHQWLFDO PHWKRG
6WDWHOHVV
EHDQV
These beans ar
all identical e
EHDQ
EHDQ
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LV,GHQWLFDO DOZD\VUHWXUQVWUXH
HYHQIRUGLIIHUHQWEHDQV
7KHLV,GHQWLFDO PHWKRGLV
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RQHEHDQZLWKDSULPDU\NH\RIEXWFOLHQWVPD\
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 33
WKHFOLHQWYLHZ
WKHUH DUH QR
'XPE 4XHVWLRQV
Q:
7HY CANT YOU JUST USE THE EQUALS METHOD
INSTEAD OF IS)DENTICAL )SNT THAT WHAT EQUALS IS FOR
A:
2EMEMBER WERE TALKING ABOUT 2EMOTE OBJECTS
4HE EQUALS METHOD COMPARES TWO OBJECTS ON THE
SAME (%!0 WHERE IS)DENTICAL COMPARES TWO 2EMOTE
OBJECTS ON THE 3%26%2
Q:
) STILL DONT SEE WHY THEY COULDNT HAVE JUST
IMPLEMENTED THE EQUALS METHOD ON THE STUB TO DO
THE SAME THING
A:
4HE EQUALS METHOD IS NOT A REMOTE METHOD
FOR ONE THING 9OU CAN ALWAYS CALL EQUALS ON A STUB
BECAUSE YOU CAN CALL IT ON ANY OBJECT ON YOUR HEAP
"UT ITS NOT PART OF THE REMOTE INTERFACE SO IT CANT BE
A REMOTE METHOD FOR EXAMPLE IT DOESNT DECLARE A
2EMOTE%XCEPTION ETC
!ND REMEMBER THE EQUALS METHOD IS USED TO SEE IF
TWO OBJECTS ON THE HEAP ARE MEANINGFULLY EQUIVALENT
4HE VENDOR CAN IMPLEMENT THE EQUALS METHOD ON
THE STUB ANY WAY IT LIKES BUT THAT STILL DOESNT TELL YOU
ANYTHING ABOUT WHATS GOING ON BACK AT THE SERVER
END *UST BECAUSE TWO STUBS DONT PASS THE EQUALS TEST
DOESNT MEAN THE SERVER DOESNT CONSIDER THE TWO %*"
OBJECTS TO BE IDENTICAL OR REFERENCING IDENTICAL BEANS 9OUR SERVER MAY BE USING 2-) STUBS FOR EXAMPLE THAT
HAVE NO LOGIC FOR HOW THEIR COMPARISONS RELATE TO
MEANINGFUL COMPARISONS OF TWO %*" OBJECTS ON THE
SERVER 2-) STUBS KNOW ABOUT 2EMOTE OBJECTS BUT THEY
DONT KNOW WHAT THOSE 2EMOTE OBJECTS REPRESENT
Q:
(OW COME THERES A METHOD IN THE %*"/BJECT
INTERFACE FOR GETTING THE BEANS HOME )F YOU DONT
(!6% THE HOME THEN HOW DID YOU GET THE BEAN IN THE
lRST PLACE
A:
4HERE ARE OTHER WAYS TO GET A REFERENCE TO AN %*"
OBJECT )TS TRUE THAT YOU CANT USE *.$) TO LOOK UP THE
%*" OBJECT ONLY THE HOME IS REGISTERED
"54 THERES NOTHING TO STOP YOU FROM PASSING AN %*"
OBJECT REFERENCE AS AN ARGUMENT OR RETURN VALUE 9OU
MIGHT HAVE A BUSINESS METHOD IN ONE BEAN WHOSE SOLE
JOB IS TO HAND YOU BACK A REFERENCE TO AN %*" OBJECT FOR A
DIFFERENT BEAN
.OW SUPPOSE YOU HAVE THIS %*" OBJECT REFERENCE TO A
BEAN WHOSE HOME YOU NEVER HAD AND NOW YOU WANT TO
MAKE MORE OF THOSE BEANS FOR YOURSELF 9OU CAN DO THAT
BY ASKING FOR THE BEANS HOME USING GET%*"(OME !ND EVEN IF YOU DO HAVE ENOUGH INFORMATION TO DO A
LOOKUP IN *.$) FOR THAT BEANS HOME *.$) LOOKUPS ARE
EXPENSIVE 9OULL SAVE SOME OVERHEAD IF YOU JUST GET THE
HOME REFERENCE FROM THE BEAN DIRECTLY
Q:
7HY CANT YOU SERIALIZE THE STUB 7HY DO WE
NEED HANDLES
A:
7E DIDNT SAY THE STUB WASNT 3ERIALIZABLE "UT
EVEN IF YOU CAN SERIALIZE IT THAT DOESNT MEAN ITS GOT
ENOUGH INFORMATION TO GET YOU BACK TO THE SAME OR
MEANINGFULLY IDENTICAL %*" OBJECT 7HEN THE STUB COMES
OVER FROM THE SERVER ITS ALREADY KNOWLEDGEABLE ABOUT
HOW TO CONTACT A PARTICULAR 2EMOTE OBJECT 7HEN THAT
STUB IS RECREATED THAT EXACT 2EMOTE OBJECT MIGHT NOT
EVEN EXIST ANY LONGER
Q:
A:
4HEN HOW WOULD THE HANDLE BE ANY BETTER
4HE HANDLE HAS THE @SMARTS TO COMMUNICATE
WITH THE SERVER AND GET BACK SOMETHING THAT IS JUST THE
SAME AS THE %*" OBJECT YOU HAD BEFORE )N OTHER WORDS
IT MIGHT NOT BE THE SAME %*" OBJECT BUT THE CLIENT WILL
NEVER BE ABLE TO TELL THE DIFFERENCE
\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 34
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 35
WKHFOLHQWYLHZ
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7EVE LOOKED AT ONLY THE 2EMOTE CLIENT INTERFACES FOR A BEAN SO FAR BUT AS
OF %*" SESSION AND ENTITY BEANS CAN EXPOSE A LOCAL CLIENT VIEW )N OTHER
WORDS CLIENT INTERFACES THAT DO NOT EXTEND JAVARMI2EMOTE
7HAT DOES THIS MEAN 4HAT THE HOME OBJECT AND %*" OBJECT ARE NOT 2EMOTE
OBJECTS 4HEYRE RUNNING IN THE SAME *6- AS THE CLIENT AND THE BEAN )N THE
ENTITY BEAN #-2 CHAPTER WELL LOOK AT WHY LOCAL INTERFACES WERE ADDED TO
THE SPEC &OR NOW THINK OF THEM AS A VERY SPECIAL CASE
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extend java.rmi.Remote
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from your Remote interfa
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 36
5HPRWHYVORFDOFOLHQWYLHZ
FOLHQWKHDS
VWXE
VHUYLFHV
&RPSRQHQWLQWHUIDFH
(-%
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No stubs!!
+RPHLQWHUIDFH
The client still canÕt get to
the bean directly, because
the server still needs a place
to intercept the call to the
bean (so the server can add
services). But this time, the
client has a local reference
to the home and component
interface objects.
&RPSRQHQWLQWHUIDFH
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
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Page 37
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 38
Return to Table of Contents
ORFDOLQWHUIDFHV
?PQKPUM\PWL[UISM[MV[MNWZ\PMTWKITKTQMV\QV\MZNIKM['
9OU ALREADY KNOW THAT THE LOCAL CLIENT INTERFACES ARE MISSING SOME OF THE METHODS
FROM THEIR 2EMOTE COUNTERPARTS ,ETS lGURE OUT WHICH ONES ARE MISSING AND WHY
,W_MVMMLPIVLTM[_Q\PTWKITQV\MZNIKM['
2EMEMBER WHY HANDLES EXIST IN %*"ˆTO GIVE YOU A 3ERIALIZABLE OBJECT THAT YOU
CAN USE TO RE ESTABLISH A STUB TO THE %*" OBJECT YOUD BEEN WORKING WITH 4HE
HANDLE IS JUST AN ABSTRACTION OF A REMOTE CONNECTION 3O DOES THIS MAKE SENSE
ON A LOCAL CLIENT
,W_MVMML-2*5M\I,I\I_Q\PTWKITQV\MZNIKM['
2EMEMBER WHAT %*"-ETA$ATA IS USED FORˆTO GET REmECTION LIKE INFO ABOUT A
BEAN )F YOU CALL GET%*"-ETA$ATA ON A BEANS 2EMOTE HOME YOU GET BACK
AN OBJECT THAT IMPLEMENTS %*"-ETA$ATA 4HAT INTERFACE %*"-ETA$ATA HAS
METHODS THAT LET YOU INTERROGATE THE BEAN AND LEARN MORE ABOUT THE CLASSES THAT
MAKE UP THE COMPONENT 7OULD A LOCAL CLIENT EVER NEED %*"-ETA$ATA
,W_MVMMLQ[1LMV\QKIT_Q\PTWKITQV\MZNIKM['
2EMEMBER WHY IS)DENTICAL EXISTSˆTO LET YOU COMPARE TWO HOME OR
COMPONENT INTERFACE REFERENCES TO SEE IF THEY REFER TO hMEANINGFULLY EQUIVALENTv
BEANS ON THE SERVER 7OULD YOU NEED TO USE IS)DENTICAL ON A LOCAL CLIENT "IG
(INT THE SERVER IS FREE TO IMPLEMENT EQUALS ANY WAY IT CHOOSES
,W_MVMMLXZQUIZaSMaQVNWZUI\QWV_Q\PTWKITQV\MZNIKM['
2EMEMBER WHY PRIMARY KEYS EXISTˆTO UNIQUELY IDENTIFY ENTITY BEANS 7OULD
YOU EVER NEED TO IDENTIFY AN ENTITY BEAN ON A LOCAL CLIENT
,W_MVMMLZMUW^MUM\PWL[_Q\PTWKITQV\MZNIKM['
2EMEMBER WHAT REMOVE IS USED FORˆTO TELL THE CONTAINER THAT YOURE DONE
WITH A BEAN FOR 3ESSION BEANS OR TO TELL THE CONTAINER TO PERMANENTLY DELETE THE
ENTITY FOR ENTITY BEANS 7OULD A LOCAL CLIENT NEED TO CALL REMOVE ON A BEAN
&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 39
WKHFOLHQWYLHZ
?PMVaW]\PQVSPIVLTM\PQVS:MUW\M
4WKITKTQMV\[LWV¼\VMMLPIVLTM[
,OCAL CLIENTS HAVE NO USE FOR A HANDLE BECAUSE HANDLES ARE
STRICTLY FOR GETTING A SAVABLE 3ERIALIZABLE OBJECT THAT KNOWS HOW
TO REESTABLISH COMMUNICATION WITH THE 2EMOTE OBJECT
A local client
Java referencehatos a plain old
the home
or component
thereÕs no needinterface, so
for handles.
no stubs,
no handles
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SORTS OF INFORMATION ABOUT ITS CLASS 7ITH 2EMOTE OBJECTS YOU DONT HAVE
THAT OPTION BECAUSE YOU CANT GET A REFERENCE TO THE CLASS OF THE 2EMOTE
OBJECT 4HE ONLY THING YOU CAN INTERROGATE ON A 2EMOTE CLIENT ARE THE
STUB OBJECTS BUT THEY CANT TELL YOU ANYTHING ABOUT THE REAL %*" OBJECT OR
(OME OBJECT
3O WHILE A 2EMOTE HOME CLIENT HAS TO USE %*"-ETA$ATA THE INTERFACE
RETURNED FROM THE %*"(OME GET%*"-ETA$ATA METHOD TO GET INFO A
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Return to Table of Contents
Page 40
ORFDOLQWHUIDFHV
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4WKITKTQMV\[[\QTTVMMLQ[1LMV\QKIT
2EMEMBER FOR A 2EMOTE CLIENT THE ONLY LOCAL COMPARISON YOU DO IS ON TWO STUB OBJECTS
USING EQUALS 4HIS DOESNT WORK WHEN YOU WANT TO COMPARE SOMETHING BACK ON THE
SERVER IN THIS CASE THE TWO %*" OBJECT REFERENCES 4HATS WHAT IS)DENTICAL IS FOR "UT LOCAL
CLIENTS HAVE THE REAL THING 4HEY HAVE THE REAL REFERENCE TO THE %*" OBJECT SO THEY CAN USE
EQUALS TO SEE IF TWO %*" OBJECT LOCAL REFERENCES ARE MEANINGFULLY EQUIVALENT "UT
THATS STILL NOT WHAT YOU WANT 4HERE IS NO GUARANTEE IN THE SPEC FOR THE RESULTS YOULL GET
WITH EQUALS 3O WHILE IT SEEMS LIKE YOU COULD JUST USE EQUALS RATHER THAN IS)DENTICAL
WITH A LOCAL CLIENT THE SPEC DOES NOT GUARANTEE THAT THE RESULTS WILL BE THE SAME "OTTOM
LINE IF YOU WANT TO KNOW IF TWO %*" OBJECT REFERENCES ARE REFERENCING THE SAME SESSION
OBJECT YOU HAVE TO USE IS)DENTICAL EVEN WHEN THE %*" OBJECT IS LOCAL
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
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Page 41
WKHFOLHQWYLHZ
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.WZ:MUW\MKTQMV\[\ _WQV\PMPWUMXT][WVMQV\PM
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2EMEMBER 2EMOTE CLIENTS HAVE THREE REMOVE METHODS AVAILABLE TWO IN THE
HOME AND ONE IN THE COMPONENT INTERFACE 4HE REMOVE THAT COMES FROM
%*"/BJECT IS SIMPLE IF YOU CALL IT YOURE SAYING YOU WANT TO REMOVE THAT VERY BEAN )N
OTHER WORDS THE BEAN WHOSE %*"/BJECT YOU USED TO CALL REMOVE !ND FOR SESSION
BEANS REMEMBER CALLING REMOVE SIMPLY TELLS THE CONTAINER THAT YOURE DONE WITH
THE BEAN )TS GOOD MANNERS AND IT IMPROVES SCALABILITY SINCE THE SERVER CAN STOP
KEEPING CLIENT SPECIlC RESOURCES ON YOUR BEHALF RATHER THAN WAITING SAY FOR YOUR
SHOPPING SESSION TO TIME OUT FROM INACTIVITY
"UT THINGS ARENT SO SIMPLE WHEN YOU CALL REMOVE ON A HOME &OR ONE THING YOU
ACTUALLY CANT REMOVE A HOME 4HE SERVER KEEPS THE BEAN HOME ALIVE WHETHER YOURE
AROUND OR NOT SO THERES NO SIGNIlCANT CLIENT SPECIlC RESOURCES 4HERES NO NEED TO
TELL THE SERVER YOURE DONE WITH THE HOME BECAUSE THE SERVER WOULD SIMPLY SAY h3O
WHATv
4HEN WHAT DOES IT MEAN TO CALL REMOVE ON A HOME
)T MEANS YOURE TELLING THE HOME TO REMOVE ONE OF THE BEANS THAT CAME FROM THAT
HOME !ND THAT MEANS YOU HAVE TO IDENTIFY WHICH BEAN YOURE TALKING ABOUT
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\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 42
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
Page 43
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WKHFOLHQWYLHZ
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)F LOCAL HOME INTERFACES DONT HAVE HANDLES THEN
THERES NO WAY YOU COULD HAVE A REMOVE METHOD THAT
TAKES A HANDLE "ECAUSE IN ORDER TO PASS A HANDLE TO
THE HOME THAT UNIQUELY IDENTIlES THE BEAN YOURE
TRYING TO REMOVE YOUD HAVE TO lRST GET THE BEANS
HANDLE !ND SINCE LOCALLY EXPOSED BEANS DONT HAVE
HANDLES YOU SEE THE PROBLEM
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A:
./ "ECAUSE YOU CANT MIX LOCAL AND 2EMOTE
INTERFACES TOGETHER /NLY A LOCAL BEAN COMES FROM A LOCAL
HOME AND VICE VERSA 3O IT WILL .%6%2 BE POSSIBLE TO HAVE
A 2EMOTE BEANS HANDLE TO GIVE TO THAT SAME 2EMOTE
BEANS HOME UNLESS THAT HOME IS ALSO 2EMOTE
7E DIDNT SAY THAT VERY WELL DID WE /+ HOW ABOUT
THISˆA 2EMOTE HOME WILL HAND OUT ONLY 2EMOTE REFERENCES
TO THE COMPONENT %*"/BJECT INTERFACE FOR THAT BEAN TYPE
AND A LOCAL HOME WILL ONLY RETURN LOCAL REFERENCES TO THE
COMPONENT %*",OCAL/BJECT INTERFACE
Q:
A:
4ELL ME AGAIN WHY YOU CANT REMOVE THE HOME
4HERES NEVER A REASON TO REMOVE THE HOME IN
OTHER WORDS TO TELL THE CONTAINER YOURE DONE WITH IT
BECAUSE THE CONTAINER MUST KEEP THE HOME AROUND WITH
OR WITHOUT YOUR INTEREST 3O IF YOU WERE ABLE TO SAY REMOVE
TO THE HOME THE CONTAINER WOULD SAY h'EEDONT FLATTER
YOURSELF BUDDY 7HAT ) DO HERE ON THE SERVER IS NOT !"/54
YOU ) COULD CARE LESS WHEN YOURE DONE WITH YOUR HOME
REFERENCEv
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 44
FRPSDULQJORFDOYV5HPRWH
+WUXIZQVO:MUW\M^[4WKITQV\MZNIKM[
4HE %*"/BJECT AND %*"(OME INTERFACES HAVE MORE METHODS THAN THE
%*",OCAL/BJECT AND %*",OCAL(OME INTERFACES BECAUSE THERE ARE METHODS
THAT DONT MAKE SENSE IN A LOCAL CONTEXT
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LQWHUIDFH!!
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LQWHUIDFH!!
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Local clients can
use reßection
they donÕt need
EJBMetaData., so
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ndle with a local
clientÑthereÕs no
stub!
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be
ans donÕt have
handles, so yo
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changes from Remote to local
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 45
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
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Page 46
ORFDOLQWHUIDFHV
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.OW THAT WEVE COVERED WHAT THE CLIENT SEES IN A LOCAL INTERFACE LETS LOOK AT
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ocalObject
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
Page 47
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WKHFOLHQWYLHZ
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7E MENTIONED EARLIER THAT LOCAL INTERFACES ARE
A VERY SPECIAL CASE FOR A CLIENT VIEW 4HEY WERE
INTRODUCED WITH VERSION OF THE %*" SPEC WHICH
THIS BOOK IS BASED ON AND THE ORIGINAL INTENT WAS
TO SUPPORT CONTAINER MANAGED RELATIONSHIPS IN
ENTITY BEANS "UT ENOUGH CUSTOMERS AND VENDORS
ASKED FOR THE ABILITY TO HAVE NON 2EMOTE INTERFACES
FOR BEANS SO THE *%% TEAM DECIDED TO MAKE IT
AVAILABLE FOR SESSION BEANS AS WELL AS ENTITY BEANS
"UT REGARDLESS OF WHICH YOU CHOOSE ITS VERY
UNLIKELY YOULL HAVE A DESIGN THAT REQUIRES BOTH
A LOCAL AND 2EMOTE CLIENT VIEW )F YOUR BEAN IS IN
A CONTAINER MANAGED RELATIONSHIP WITH ANOTHER
ENTITY BEAN YOULL LEARN ALL ABOUT THIS IN THE ENTITY
CHAPTERS YOU HAVE NO CHOICE 4HE BEAN MUST
EXPOSE ITSELF LOCALLY !ND IN THAT CASE ITS ALMOST
IMPOSSIBLE TO THINK OF A REASON TO ALSO HAVE THAT
SAME BEAN EXPOSED TO 2EMOTE CLIENTS FOR OTHER
PURPOSES
*UST KNOW THAT IT IS LEGAL TO HAVE BOTH
"UT YOU CAN NEVER EVER EVER MIX AND MATCH
! 2EMOTE HOME INTERFACE CAN GIVE OUT ONLY 2EMOTE
COMPONENT INTERFACE REFERENCES IN OTHER WORDS A
STUB TO THE 2EMOTE %*"/BJECT ! LOCAL HOME CAN
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 48
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 49
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! 2EMOTE INTERFACE MUST HAVE 2EMOTE%XCEPTION DECLARED ON EVERY METHOD 4HAT MEANS THE
CLIENT USING A 2EMOTE INTERFACE MUST DEAL WITH 2EMOTE%XCEPTION FOR EVERY 2EMOTE METHOD CALL
"UT LOCAL INTERFACES DONT HAVE THAT RESTRICTION 4HE ONLY METHODS IN A LOCAL CLIENT INTERFACE THAT
MUST DECLARE EXCEPTIONS ARE THE CREATE AND REMOVE METHODS FOR SESSION BEANS ENTITY BEANS
ALSO HAVE A lNDER METHOD THAT DECLARES A &INDER%XCEPTION 7E HAVE A WHOLE CHAPTER DEVOTED TO EXCEPTIONS IN %*" SO WE WONT GO INTO THE DETAILS NOW BUT
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
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Page 50
ORFDOFOLHQWV
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#OMPARE THIS TO THE CODE MODIlCATIONS YOU MADE ON THE PREVIOUS SHARPEN
4O HELP SHOW THAT THE CALLS TO THE HOME AND COMPONENT INTERFACE ARE NO
LONGER 2EMOTE WEVE MADE THE EXCEPTION HANDLING MORE lNE GRAINED .OTICE
THAT WERE NOT CATCHING A 2EMOTE%XCEPTION
LPSRUWMDYD[QDPLQJ LPSRUWKHDG¿UVW LPSRUWMDYD[HME we got rid of javax.rmi and
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 51
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7EVE SEEN HOW THE INTERFACES CHANGE AND HOW THE CLIENT CODE HAS TO
CHANGE WHEN YOU GO FROM A 2EMOTE TO LOCAL CLIENT VIEW "UT WHAT ABOUT THE
BEAN CLASS ITSELF 7HAT DO YOU THINK $OES THE BEAN CODE NEED TO CHANGE
IF YOURE GOING TO DEPLOY IT WITH A LOCAL CLIENT VIEW INSTEAD OF A 2EMOTE CLIENT
VIEW 7HAT IF YOU PLAN TO DEPLOY IT WITH BOTH A LOCAL AND 2EMOTE CLIENT VIEW
&OR NOW LETS ASSUME THAT THE ONLY METHOD THAT MATTERS IS THE BEANS
BUSINESS METHOD (ERES HOW IT LOOKS IN THE ORIGINAL BEAN CLASS
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 52
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 53
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
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Page 54
5HPRWHYVORFDO
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Q:
3O )M STILL NOT CLEAR IF THE
BEAN -534 ALWAYS KNOW IF THE CLIENT
IS 2EMOTE OR LOCAL
A:
)TS NOT THAT THE BEAN MUST
BUT RATHER THAT THE BEAN MIGHT HAVE
TO KNOW )F IT MATTERS THAT THE BEAN
IS WORKING ON A THE CALLERS OBJECT
VIA A COPY OF THE CALLERS REFERENCE
AS OPPOSED TO A COPY OF THE CALLERS
OBJECT YOUR BEAN CODE MIGHT HAVE
TO CHANGE !ND THAT GOES FOR RETURN
VALUES TOO )F IT MATTERS THAT THE CALLING
METHOD GETS BACK A COPY OF A REFER
ENCE VS A COPY OF AN OBJECT THE BEAN
CODE MIGHT HAVE TO CHANGE
Q:
"UT ) THOUGHT THAT CHOOSING TO
DEPLOY A BEAN WITH LOCAL VS 2EMOTE
CLIENT VIEWS WAS JUST A MATTER OF
SWITCHING A SWITCH AT DEPLOY TIME
A:
./ ./ ./ ,ETS IMAGINE THAT
YOU DID WRITE TWO SETS OF INTERFACES
ONE FOR A LOCAL CLIENT VIEW AND ONE
FOR A 2EMOTE CLIENT VIEW )T IS TRUE
THAT AT DEPLOYMENT YOU COULD DECIDE
WHICH OF THE TWO VIEWS YOU WANTED TO
EXPOSE OR BOTH "UT THAT WORKS ONLY
IF THE BEAN CODE DOESNT CARE WHERE
THE CLIENT IS ! BEAN METHOD WITH NO
ARGUMENTS OR RETURN VALUES MIGHT BE
SAFE REGARDLESS OF HOW THE CLIENT IS
ACCESSING IT
/NE SOLUTION MIGHT BE TO WRITE THE
BEAN CODE ASSUMING THE BEAN IS
ALWAYS GETTING A COPY AND THEN IF THE
CLIENT IS LOCAL HAVE THE CLIENT MAKE
A COPY CLONE OF THE OBJECT BEFORE
PASSING IT /R FOR RETURN VALUES YOU
MIGHT ALWAYS HAVE THE BEAN MAKE A
COPY BEFORE HANDING IT BACK 4HAT WAY
THE BEAN NEVER HAS TO WORRY THAT A
LOCAL CLIENT MIGHT BE MODIFYING THE
BEANS OBJECT
!ND A LOCAL CLIENT WONT HAVE CODE
TO HANDLE THE 2EMOTE%XCEPTIONS OR
NARROW THE STUBS
Q:
4HE BOTTOM LINE IS THAT DEPLOYING A
BEAN WITH A 2EMOTE VS LOCAL CLIENT
VIEW IS A "IG $EAL )TS A COMMITMENT
4HE CLIENT HAS TO KNOW IN ADVANCE
4HEN ITS JUST ABOUT
ARGUMENTS AND RETURN VALUES )S
THERE ANY OTHER REASON YOU COULDNT
DEPLOY A BEAN AND MAKE THE
DECISION FOR 2EMOTE VS LOCAL VIEW AT
DEPLOY TIME
A:
4HERE IS ANOTHER REASON 4HE
CLIENT CODE %VEN IF THE BEAN DOESNT
NEED TO KNOW HOW ITS CLIENT IS
ACCESSING IT THE CLIENT MUST KNOW !
CLIENT WRITTEN TO ACCESS A BEAN LOCALLY
WOULDNT WORK IF THE BEANS 2EMOTE
CLIENT INTERFACES AND VICE VERSA
Q:
A:
7HY NOT
4HE CLIENT MUST KNOW IN
ADVANCE WHETHER ITS ACCESSING A
BEANS 2EMOTE OR LOCAL CLIENT VIEW
BECAUSE THE INTERFACES THEMSELVES
ARE DIFFERENT 0OLYMORPHICALLY YOU
CANT USE THE 2EMOTE AND LOCAL
VIEWS INTERCHANGEABLY BECAUSE THE
INTERFACES THEMSELVES ARE DIFFERENT
4HERES NO WAY THE CLIENT CAN BE
KEPT BLISSFULLY IGNORANT BECAUSE
THE BEHAVIOR OF THE BEAN IS DIFFERENT
2EMEMBER A 2EMOTE CLIENT MUST
HANDLE 2EMOTE%XCEPTIONS AND
NARROW THE 2EMOTE STUB COMING BACK
FROM THE LOOKUP !ND A 2EMOTE CLIENT
IS EXPOSED TO METHODS IN THE BEANS
CLIENT INTERFACESˆMETHODS THAT
DONT EXIST IN THE LOCAL INTERFACES 3O A
2EMOTE CLIENT MIGHT FOR EXAMPLE TRY
TO CALL A GET(ANDLE METHOD ON THE
LOCAL COMPONENT INTERFACE A METHOD
CALL THAT WOULD NEVER WORK
Q:
#AN YOU GET AROUND THIS BY
DECLARING YOUR 2EMOTE%XCEPTIONS
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Page 56
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
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Page 57
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Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
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Page 58
FRIIHHFUDPPRFNH[DP
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 3. Exposing Yourself
Page 59
Return to Table of Contents
WKHFOLHQWYLHZ
4
7HEN COMPARING TWO SESSION OBJECTS WHAT IS TRUE #HOOSE ALL THAT APPLY
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HOME WILL ALWAYS RETURN TRUE
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REFERENCES
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\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
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Page 60
FRIIHHFUDPPRFNH[DP
0RFN([DP$QVZHUV
1
7HICH CAPABILITIES ARE PROVIDED BY BOTH REMOTE AND LOCAL HOME INTERFACES FOR
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&KDSWHU
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 3. Exposing Yourself
Return to Table of Contents
Page 61
WKHFOLHQWYLHZ
4
7HEN COMPARING TWO SESSION OBJECTS WHAT IS TRUE #HOOSE ALL THAT APPLY
(spec: 65-66)
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R" 5SING THE IS)DENTICAL METHOD STATEFUL SESSION BEANS FROM THE SAME
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e()
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\RXDUHKHUH
Chapter 3. Exposing Yourself
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Table of Contents
Chapter 4. Being a Session Bean.................................................................. 1
Section 4.1. OBJECTIVES: Session Beans...................................................................................................................................... 2
Section 4.2. Exploring the session bean lifecycle........................................................................................................................... 4
Section 4.3. You remember how it all works, right ? Getting and using a stateful session bean.................................................. 6
Section 4.4. Stateful Session Bean, CREATION............................................................................................................................. 7
Section 4.5. There's obviously more to the bean's lifecycle than just creation and business methods......................................... 8
Section 4.6. Container Callbacks, for the special moments in a bean's life................................................................................... 9
Section 4.7. Container Callbacks come from TWO places:.......................................................................................................... 10
Section 4.8. Implementing the container callbacks...................................................................................................................... 11
Section 4.9. There are no Dumb Questions.................................................................................................................................. 14
Section 4.10. Sharpen your pencil................................................................................................................................................. 14
Section 4.11. Sharpen your pencil.................................................................................................................................................. 15
Section 4.12. Bean creation: when an object becomes a bean...................................................................................................... 16
Section 4.13. Bean things you can do during creation: stateful session bean)............................................................................ 24
Section 4.14. Bean Use: what happens AFTER creation.............................................................................................................. 26
Section 4.15. Bean things you can do within business methods:................................................................................................. 27
Section 4.16. Passivation: a stateful bean's chance at scalability................................................................................................. 28
Section 4.17. There are no Dumb Questions................................................................................................................................ 30
Section 4.18. Your job for passivation: make your state passivatable!........................................................................................ 31
Section 4.19. There are no Dumb Questions................................................................................................................................ 33
Section 4.20. Sharpen your pencil................................................................................................................................................ 33
Section 4.21. Bean things you can do in ejbActivate and ejbPassivate()..................................................................................... 35
Section 4.22. Bean Removal: when beans die.............................................................................................................................. 36
Section 4.23. Complaints about bean removal............................................................................................................................. 41
Section 4.24. Bean things you can do in ejbRemove()................................................................................................................. 44
Section 4.25. Implementing the AdviceBean as a stateFUL bean............................................................................................... 45
Section 4.26. BRAIN POWER....................................................................................................................................................... 45
Section 4.27. Things you can add if the bean is stateFUL............................................................................................................ 45
Section 4.28. There are no Dumb Questions................................................................................................................................ 45
Section 4.29. AdviceStatefulBean code........................................................................................................................................ 46
Section 4.30. AdviceStatefulBean CLIENT code.......................................................................................................................... 47
Section 4.31. Sharpen your pencil................................................................................................................................................ 48
Section 4.32. Deploying a stateful bean....................................................................................................................................... 49
Section 4.33. Compared to stateful beans, stateless beans have a simple life............................................................................. 50
Section 4.34. Bean things you can do from stateless bean methods............................................................................................ 56
Section 4.35. Writing a Session Bean:your job as Bean Provider................................................................................................ 58
Section 4.36. Sharpen your pencil................................................................................................................................................ 59
Section 4.37. Sharpen your pencil: Who does What?................................................................................................................... 67
Section 4.38. SessionContext : You need it more than it needs you............................................................................................ 68
Section 4.39. Overheard at THE TiKiBEAN LoUNGE................................................................................................................. 70
Section 4.40. What's allowed?....................................................................................................................................................... 71
Section 4.41. COFFEE CRAM: Mock Exam.................................................................................................................................. 72
Section 4.42. COFFEE CRAM: Mock Exam Answers................................................................................................................... 79
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 1
session bean lifecycle
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 2
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 3
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 4
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.OW IMAGINE YOURE THE CLIENT 7HATS YOUR MOTIVATION 7HAT DO YOU NEED TO
KNOW ABOUT HOW THE #ONTAINER WORKS !ND WHAT IF YOURE THE #ONTAINER 7HAT
DO YOU HAVE TO DO TO MANAGE A BEANS LIFE AND WHEN DO YOU HAVE TO DO IT
)F YOURE THE "EAN 0ROVIDER WHAT DO YOU HAVE TO KNOW ABOUT THE BEANS LIFECYCLE
IN ORDER TO WRITE CODE THAT WORKS 7HAT IF YOU WANT THAT CODE TO BE EFlCIENT
)N THIS CHAPTER WE LOOK AT THE ENTIRE WORLD OF A SESSION BEAN AND WE DO IT FROM
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 6
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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AND PASSIVATION OF STATEFUL SESSION BEANS !ND WHAT REALLY DOES HAPPEN
WHEN A BEAN IS CREATED 7HAT MAKES BEAN CREATION DIFFERENT FROM PLAIN
OLD OBJECT CONSTRUCTION
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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&OR STATELESS SESSION BEANS THERE WILL BE EXACTLY lVE CONTAINER CALLBACKS
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THE STATELESS BEANS CREATE IS ALWAYS A NO ARG YOU KNOW THAT THE BEANS
EJB#REATE WILL ALWAYS BE A NO ARG
&OR STATEFUL BEANS REMEMBER THERE MUST BE AT LEAST ONE CREATE BUT THERE CAN
BE MORE INCLUDING BOTH OVERLOADED CREATE METHODS AND CREATESOMETHING
METHODS &OR EXAMPLE A STATEFUL BEAN HOME MIGHT HAVE THREE CREATE METHODS
CREATE CREATE3TRING S CREATE"IG#USTOMER3TRING S 4HAT WOULD MEAN
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 11
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DEPEND ON ANYTHING ELSE THAT HAPPENS AT OTHER TIMES IN THE BEANS LIFE 9OULL NOTICE
THAT WE ARE SAVING THE 3ESSION#ONTEXT PARAMETER WE GET FROM THE SET3ESSION#ONTEXT
CONTAINER CALLBACK BUT WE ARENT USING IT IN THIS CODE ,ATER IN THIS CHAPTER YOULL
LEARN WHY YOU MIGHT WANT TO ASSIGN THE CONTEXT TO AN INSTANCE VARIABLE AND THE
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 12
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 13
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 14
Return to Table of Contents
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WHY YOUR BEAN CLASS CANT EXTEND A CLASS THAT IMPLEMENTS THE
3ESSION"EAN INTERFACE
A:
4HE !0) DOESNT HAVE ADAPTER CLASSES FOR 3ESSION"EAN
IMPLEMENTATIONS IE A CLASS THAT IMPLEMENTS ALL OF THE METHODS "UT
THERES NO REASON YOU CANT MAKE ONE YOURSELF +EEP IN MIND THOUGH
THAT WITH REAL WORLD BEANS YOU PROBABLY WILL HAVE CODE IN ONE OR MORE
OF THE METHODS !ND YOU MIGHT EVEN BE WORKING WITH A BEAN AWARE )$%
THAT PUTS THE METHODS IN FOR YOU ANYWAY
3TILL IT MIGHT BE HANDY TO MAKE YOURSELF A GENERIC BEAN THAT YOU
TYPICALLY EXTEND FROM THAT HAS ALL OF THE METHODS FROM 3ESSION"EAN
7ITH STATELESS BEANS ESPECIALLY YOU HAVE TO IMPLEMENT EJB!CTIVATE AND
EJB0ASSIVATE EVEN THOUGH THEYLL NEVER BE CALLED 3TATELESS BEANS ARE
NEVER PASSIVATED YOULL SEE MORE ON THAT LATER IN THE CHAPTER
Q:
) JUST REMEMBERED THAT ) READ SOMEWHERE THAT ENTERPRISE BEANS
DONT SUPPORT INHERITANCE 7HATS THAT ABOUT
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!H A COMMON MISCONCEPTION 7ELL SORT OF %*" SUPPORTS REGULAR
*AVA CLASS INHERITANCE BUT HAS NO CONCEPT OF BEAN INHERITANCE !ND NOW
YOURE ASKING h7HAT THE HECK IS THE DIFFERENCEv 9OU ALREADY KNOW WHAT
CLASS INHERITANCE IS ITS THE THING YOU DO IN *AVA WHEN ONE CLASS EXTENDS
ANOTHER !ND YOU CAN DO THAT WITH A BEAN JUST LIKE ANY OTHER CLASS
"UT BEAN INHERITANCE IF IT WERE SUPPORTED WOULD MEAN THAT A BEAN
CLASS COULD EXTEND ANOTHER BEAN CLASS AND INHERIT NOT JUST THE CLASS
INHERITABLE MEMBERS BUT ALSO ITS BEANNESS 7HAT KIND OF BEANNESS
MIGHT BE INHERITABLE *UST IN CASE THEY DO DECIDE TO SUPPORT THIS IN
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SUPPORT BEAN INHERITANCE
/NE IDEA MIGHT BE TO HAVE YOUR BEAN SUBCLASS INHERIT SOME OF THE
DEPLOYMENT DESCRIPTOR SETTINGS OF ITS SUPERCLASS AND THEN OVERRIDE THE
ONES IT WANTS TO CHANGE WITH A MUCH SMALLER INCOMPLETE DEPLOYMENT
DESCRIPTOR 4HAT MIGHT BE COOL WERE NOT SURE "UT RIGHT NOW ITS JUST OUR
LITTLE FANTASY
)N THE MEANTIME GO AHEAD AND LET YOUR BEAN EXTEND ANOTHER CLASS IF IT
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 15
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 16
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SECURITY INFO ABOUT THE CLIENT OR LOOK UP SPECIAL DEPLOY
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AT WHICH AN OBJECT BECOMES A CARD CARRYING BEAN AND WHAT
THAT MEANS TO YOU AS THE DEVELOPER
*WeÕre not explaining the whole Schroedinger reference here, except to
say that it involves cats (animal-lovers be warned) and subatomic physics.
For more info, look for Head First Quantum Physics in the future. WeÕre
serious. Serious for us, anyway.
&KDSWHU
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 17
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LETS THE BEAN DO THINGS LIKE GET SECURITY INFORMATION
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 18
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Page 19
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 4. Being a Session Bean
Page 21
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Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Page 25
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 26
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 30
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WHICH A SERVER CAN FIGURE OUT IF
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AWAY EITHER BY SHUTTING DOWN THE
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THE NETWORK
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ASSUME THAT THE %*" SERVER DOESNT
SUPPORT THIS SO YOURE STUCK WITH
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 31
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 32
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 33
VHVVLRQEHDQOLIHF\FOH
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SERIALIZATION TO GET THE JOB DONE "UT THERES A LITTLE TEENY COMMENT IN THE SPEC WHICH
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RELY ON TRANSIENT TO GIVE YOU BACK YOUR DEFAULTS SO AFTER
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VARIABLES YOURSELF IN EJB!CTIVATE Q:
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4HIS IS A CLASSIC SERIALIZATION ISSUE NOT SPECIFIC TO
PASSIVATION 4HE USUAL TRICK IS TO INTERROGATE THE NON
3ERIALIZABLE OBJECT TO GET ALL THE IMPORTANT STATE OUT OF
IT AND STICK THAT STATE INTO INSTANCE VARIABLES THAT ARE
3ERIALIZABLE 4HEN DURING EJB!CTIVATE USE THE VALUES YOU
WERE ABLE TO SAVE TO RECONSTRUCT THE NON 3ERIALIZABLE OBJECT
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VARIABLE AND THE #OLLAR ISNT 3ERIALIZABLE )N EJB0ASSIVATE
CALL GETTERS ON THE #OLLAR TO RETRIEVE THE VALUES THAT MATTER
LIKE GET#OLOR GET3IZE ETC 3AVE THOSE VALUES IN INSTANCE
VARIABLES IN THE BEAN THEN IN EJB!CTIVATE INSTANTIATE A NEW
#OLLAR AND USE THE #OLLAR ATTRIBUTES YOU SAVED AS ARGUMENTS
TO SETTERS ON THE NEW #OLLAR OBJECT
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 34
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 36
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Page 38
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 44
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 45
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 46
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 47
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 50
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 60
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 61
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 62
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 63
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 64
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 65
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 66
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
Return to Table of Contents
Page 71
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 73
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7HICH ARE VALID REMOTE COMPONENT INTERFACES FOR A SESSION BEAN #HOOSE ALL
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
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Page 74
FRIIHHFUDPPRFNH[DP
7
7HAT IS TRUE ABOUT A SESSION BEANS LIFECYCLE #HOOSE ALL THAT APPLY
R! )F A BUSINESS METHOD THROWS A SYSTEM EXCEPTION THE BEAN WILL BE
PASSIVATED
R" ! PASSIVATED BEAN MUST BE ACTIVATED BEFORE IT CAN BE REMOVED
R# ! STATELESS SESSION BEANS REMOVAL MUST BE INITIATED BY THE CLIENT NOT THE
CONTAINER
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INTERFACE
8
7HICH ARE REQUIRED OF THE BEAN PROVIDER TO ENSURE THAT A SESSION BEAN IS
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R! 4HE PROVIDER MUST CALLHME3DVVLYDWH R" 4HE PROVIDER MUST ALWAYS ADD BUSINESS LOGIC TO THEHME3DVVLYDWH METHOD IF THE BEAN IS STATEFUL
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HME3DVVLYDWH
COMPLETES
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TRANSIENT WILL BE LOST
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OBJECT WILL BE NOT SURVIVE PASSIVATION IF THE 3ESSION#ONTEXT OBJECT IS NOT
SERIALIZABLE
9
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DEMARCATION FROM WHICH METHODS CAN YOU ACCESS ANOTHER BEAN #HOOSE
ALL THAT APPLY
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 75
VHVVLRQEHDQOLIHF\FOH
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.OTE 4HE REAL EXAM HAS SEVERAL TYPES OF @DRAG AND DROP QUESTIONS THAT
WERE GOING TO DO A LAME JOB OF SIMULATING WITH THIS QUESTION
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CAN BE FOUND ON THE RIGHT ! MATCH IS CORRECT IF THE METHOD IS EITHER DECLARED
IN OR INHERITED BY THE INTERFACE .OTE 4HERE MAY BE SOME MANY TO ONE AND
ONE TO MANY RELATIONSHIPS IN YOUR ANSWER
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3ESSION3YNCHRONIZATION
" GET5SER4RANSACTION
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7HAT IS TRUE ABOUT A SESSION BEANS LIFECYCLE #HOOSE ALL THAT APPLY
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THE CLIENT INVOKES THE FUHDWH
STATELESS BEAN
METHOD ON THE HOME INTERFACE OF A
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7HICH OF THE FOLLOWING METHODS ARE CONTAINER CALLBACK METHODS #HOOSE ALL
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 76
FRIIHHFUDPPRFNH[DP
13
)N WHAT CASES WILL THE CONTAINER FAIL TO CALL EJB2EMOVE ON A SESSION BEAN
#HOOSE ALL THAT APPLY
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HME&UHDWH
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ONLY STATELESS SESSION BEANS
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THAT APPLY
R!
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7HICH METHODS ALLOW BOTH STATEFUL AND STATELESS SESSION BEANS WITH BEAN
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#HOOSE ALL THAT APPLY
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 77
VHVVLRQEHDQOLIHF\FOH
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&OR THIS DRAG AND DROP TYPE QUESTION YOU CAN USE EACH ELEMENT ONLY ONCE
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IMPLEMENTED
R! ONLY STATEFUL SESSION BEANS
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Page 78
Return to Table of Contents
FRIIHHFUDPPRFNH[DP
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7HICH STATEMENTS ARE TRUE FOR STATELESS SESSION BEAN INSTANCES #HOOSE ALL
THAT APPLY
R! !NY INSTANCE CAN BE USED FOR ANY CLIENT
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R$ 4HEY CAN BE PASSIVATED
R% 4HEY DO NOT SUPPORT TRANSACTIONS
&KDSWHU
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 79
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s what entity
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bean
R" 4HE CLIENT MUST CALL THE EJB!CTIVATE METHOD BEFORE CALLING ANY BUSINESS - only the container calls
ejbActivate()
METHODS
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2
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7HICH LISTS CORRECTLY SEQUENCE SOME OF THE STEPS IN A SESSION BEANS LIFECYCLE
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remember, passivation could be seri
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 80
PRFNH[DPDQVZHUV
4
7HICH ARE VALID REMOTE COMPONENT INTERFACES FOR A SESSION BEAN #HOOSE ALL
THAT APPLY
(spec: 97)
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 81
VHVVLRQEHDQOLIHF\FOH
7
7HAT IS TRUE ABOUT A SESSION BEANS LIFECYCLE #HOOSE ALL THAT APPLY
R! )F A BUSINESS METHOD THROWS A SYSTEM EXCEPTION THE BEAN WILL BE -
(spec: 79, 88)
lled
no, the bean is ki
PASSIVATED
R" ! PASSIVATED BEAN MUST BE ACTIVATED BEFORE IT CAN BE REMOVED - nope
R# ! STATELESS SESSION BEANS REMOVAL MUST BE INITIATED BY THE CLIENT NOT THE
CONTAINER
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INTERFACE
8
7HICH ARE REQUIRED OF THE BEAN PROVIDER TO ENSURE THAT A SESSION BEAN IS
SUCCESSFULLY PASSIVATED #HOOSE ALL THAT APPLY
(spec: 71-72)
R! 4HE PROVIDER MUST CALLHME3DVVLYDWH R" 4HE PROVIDER MUST ALWAYS ADD BUSINESS LOGIC TO THEHME3DVVLYDWH METHOD IF THE BEAN IS STATEFUL
R# 4HE PROVIDER MUST NOT CLOSE ANY DATABASE CONNECTIONS BEFORE
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COMPLETES
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9
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DEMARCATION FROM WHICH METHODS CAN YOU ACCESS ANOTHER BEAN #HOOSE
ALL THAT APPLY
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 82
PRFNH[DPDQVZHUV
10
(API docs)
.OTE 4HE REAL EXAM HAS SEVERAL TYPES OF @DRAG AND DROP QUESTIONS THAT
WERE GOING TO DO A LAME JOB OF SIMULATING WITH THIS QUESTION
-ATCH THE METHODS ON THE LEFT WITH THE INTERFACES IN WHICH THOSE METHODS
CAN BE FOUND ON THE RIGHT ! MATCH IS CORRECT IF THE METHOD IS EITHER DECLARED
IN OR INHERITED BY THE INTERFACE .OTE 4HERE MAY BE SOME MANY TO ONE AND
ONE TO MANY RELATIONSHIPS IN YOUR ANSWER
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" GET5SER4RANSACTION
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11
1
2
1
2
2
3
2,4
3ESSION3YNCHRONIZATION
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7HAT IS TRUE ABOUT A SESSION BEANS LIFECYCLE #HOOSE ALL THAT APPLY
R! 4HE CONTAINER WILL ALWAYS CREATE A NEW SESSION BEAN INSTANCE WHEN
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STATELESS BEAN - Container makes stateless beans whenever it wants
R" 4HE CONTAINER WILL ALWAYS CALL HME5HPRYH
THE UHPRYH
WHEN THE CLIENT INVOKES
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the pool
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Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 4. Being a Session Bean
Return to Table of Contents
Page 83
VHVVLRQEHDQOLIHF\FOH
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)N WHAT CASES WILL THE CONTAINER FAIL TO CALL EJB2EMOVE ON A SESSION BEAN
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14
15
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)F A TIMEOUT OCCURS WHILE THE BEAN IS IN THE METHOD READY STATE
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ly
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7HICH METHODS ALLOW BOTH STATEFUL AND STATELESS SESSION BEANS WITH BEAN
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#HOOSE ALL THAT APPLY
R!
R"
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(spec: 82)
(spec: 70)
ONLY STATEFUL SESSION BEANS
ONLY STATELESS SESSION BEANS
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&OR SESSION BEANS WHICH ARE THE RESPONSIBILITY OF THE #ONTAINER #HOOSE ALL
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might be
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\RXDUHKHUH
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 4. Being a Session Bean
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Page 84
PRFNH[DPDQVZHUV
17
&OR THIS DRAG AND DROP TYPE QUESTION YOU CAN USE EACH ELEMENT ONLY ONCE
7HICH INTERFACE SHOULD BE MATCHED WITH WHICH FACT SO THAT ALL FOUR MATCHES
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R# 4HEIR COMPONENT INTERFACE METHODS CAN BE @PRIVATE
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&OR WHICH TYPE OF BEAN CAN THE 3ESSION3YNCHRONIZATION INTERFACE BE
IMPLEMENTED
(spec: 75)
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&KDSWHU
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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VHVVLRQEHDQOLIHF\FOH
21
7HICH STATEMENTS ARE TRUE FOR STATELESS SESSION BEAN INSTANCES #HOOSE ALL
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R# #ONVERSATIONAL STATE MUST BE RETAINED ACROSS TRANSACTIONS
R$ 4HEY CAN BE PASSIVATED
R% 4HEY DO NOT SUPPORT TRANSACTIONS
\RXDUHKHUH
Chapter 4. Being a Session Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Table of Contents
Chapter 5. Entities Are Persistent................................................................ 1
Section 5.1. OBJECTIVES: Entity Beans........................................................................................................................................ 2
Section 5.2. What's an entity bean?................................................................................................................................................ 3
Section 5.3. Entities vs. Entity Beans............................................................................................................................................. 4
Section 5.4. There are no Dumb Questions.................................................................................................................................... 5
Section 5.5. There are no Dumb Questions.................................................................................................................................... 6
Section 5.6. Entity beans from the client's point of view............................................................................................................... 7
Section 5.7. Entity bean overview................................................................................................................................................... 8
Section 5.8. Entity bean overview................................................................................................................................................... 9
Section 5.9. A very simple Customer entity bean......................................................................................................................... 10
Section 5.10. An entity bean's client view...................................................................................................................................... 11
Section 5.11. Entity bean Remote component interface............................................................................................................... 12
Section 5.12. Entity bean Remote component interface............................................................................................................... 13
Section 5.13. Rules for the Remote component interface............................................................................................................. 14
Section 5.14. Entity bean Remote home interface........................................................................................................................ 15
Section 5.15. What does the client really want from an entity bean home?................................................................................. 16
Section 5.16. Entity bean Remote component interface............................................................................................................... 17
Section 5.17. When finders have a dark side................................................................................................................................. 18
Section 5.18. There are no Dumb Questions................................................................................................................................. 19
Section 5.19. Home business methods to the rescue................................................................................................................... 20
Section 5.20. Rules for the Remote home interface..................................................................................................................... 21
Section 5.21. Sharpen your pencil................................................................................................................................................. 22
Section 5.22. Session bean create() vs. entity bean create()........................................................................................................ 23
Section 5.23. Session bean remove() vs. entity bean remove().................................................................................................... 24
Section 5.24. Entity/bean/instance death.................................................................................................................................... 27
Section 5.25. Client calls remove()............................................................................................................................................... 28
Section 5.26. Entity bean client view............................................................................................................................................ 29
Section 5.27. COFFEE CRAM....................................................................................................................................................... 30
Section 5.28. COFFEE CRAM....................................................................................................................................................... 33
Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 1
entity bean intro
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Page 3
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DATABASE !ND THAT MEANS AN INDIVIDUAL ROW IN A TABLE MAPS TO A UNIQUE ENTITY BEAN
4HE OBJECT TO RELATIONAL /2 MAPPING COULD BE A LOT MORE COMPLEX THAN A SIMPLE ONE
ROW EQUALS ONE BEAN SCENARIO BUT WELL GET INTO THAT IN THE NEXT CHAPTER
%NTITY BEANS ARE DATA OBJECTS 4HEY ARETHINGS .OUNS !S OPPOSED TO SESSION BEANS
WHICH ARE PROCESSES 6ERBS %NTITY BEANS MIGHT REPRESENT THINGS LIKE PEOPLE PRODUCTS
ORDERS BOOKINGS INVENTORY ANIMALSTHINGS %NTITY BEANS WOULD NOT REPRESENT
THINGS LIKE CREDIT CARD VERIlCATION ADVISOR SERVICE ORDER SUBMISSION MEMBERSHIP
REGISTRATION PROCESSES
/F COURSE IN VIRTUALLY ALL WELL DESIGNED %*" APPLICATIONS ENTITY BEANS WILL BE COMBINED
WITH SESSION BEANS WHERE THE CLIENT INTERACTS WITH THE PROCESS SESSION BEAN AND THE
SESSION BEAN USES ENTITY BEANS WHEN IT NEEDS DATA AS PART OF THE PROCESS
\RXDUHKHUH
Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Page 4
HQWLW\EHDQV
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!N ENTITY IS THE REAL THING THAT THE ENTITY BEAN REPRESENTS
)T DOESNT WORK IN REVERSE 4HE ENTITY DOES NOT REPRESENT
THE ENTITY BEAN 4HAT MIGHT SEEM LIKE A SUBTLE POINT BUT
ITS NOT 4HE DIFFERENCE IS IN KNOWING WHICH ONE IS REAL
AND WHICH ONE IS SIMPLY A VIEW OF THE REAL THING
)N OTHER WORDS IF YOU DELETE THE REAL ENTITY THE THING
IN THE DATABASE THE ENTITY BEAN DISINTEGRATES 0OOF "UT
IF THE ENTITY BEAN DIES AS AN INSTANCE ON THE HEAP IT
DOESNT KILL THE REAL ENTITY IN THE DATABASE "Y THE WAY
WERE NOW GOING TO SAY @DATABASE INSTEAD OF @UNDERLYING
PERSISTENT STORE BUT YOU AND ) BOTH KNOW THAT THESE TWO
ARE NOT NECESSARILY SYNONYMOUS AND THAT THE @UNDERLYING
PERSISTENT STORE NEED NOT BEˆBUT USUALLY ISˆA DATABASE
4HERE WEVE SAID IT
3O YOU WONT HAVE THE RIGHT PERSPECTIVE IF YOU THINK OF
THE ENTITY BEAN AS SOME DATA OBJECT THAT HAPPENS TO BE
BACKED UP TO PERSISTENT STORAGE )N NEARLY ALL APPLICATIONS
THE VAST MAJORITY OF ENTITIES USED IN THE APP ARE NOT
REALIZED AS ENTITY BEANS AT ANY GIVEN TIME )NSTEAD MOST
ENTITY BEANS BECOME A REPRESENTATION OF AN UNDERLYING
ENTITY ONLY WHEN THAT PARTICULAR ENTITY IS NEEDED IN THE
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ENTITY BEANS ACTIVELY REPRESENTING CUSTOMER ENTITIES
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THERE IN THE DATABASE WAITING FOR A CLIENT PROCESS TO
NEED THEM
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DESCRIBED YOU HAVE ACTORS EACH PLAYING A DIFFERENT
ROLE OF SOMEONE IN THE DATABASE "UT THE OTHER ENTITIES IN THE DATABASEˆTHE OTHER CUSTOMERSˆDO NOT
HAVE ANYONE PLAYING THEM
"UT AS SOON AS A CLIENT COMES ALONG AND TRIES TO GET ONE
OF THOSE OTHER SAY TO CHANGE THAT CUSTOMERS
ADDRESS OR CHECK ITS CREDIT LIMIT AN ACTOR ENTITY BEAN
WILL BE CHOSEN TO PLAY THE ROLE OF THAT SELECTED CUSTOMER
&KDSWHU
Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 5
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HQWLW\EHDQLQWUR
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*UST SO )VE GOT THIS STRAIGHT
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THE DATABASE THAT ARE ACTIVELY NEEDED
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TO LOAD THEM ALL IN .OT NECESSARILY
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RESOURCE REQUIREMENTS ESPECIALLY IF
THE DATA IN THE UNDERLYING DATABASE
CONTINUES TO GROW JUST THINK OF HOW
&!34 IT WOULD BE
!LTHOUGH THERE IS NOTHING IN THE
SPEC THAT REQUIRES THIS A VENDOR CAN
CHOOSE TO LET YOU CONFIGURE THE APP
IN SUCH A WAY THAT IT DOES PRE LOAD
ALL THE ENTITIES IN THE DATABASE INTO
BEANS 4HAT GIVES YOU ESSENTIALLY A
LIGHTENING FAST IN MEMORY DATABASE
THAT STILL SYNCHRONIZES ITSELF WITH THE
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A MOMENT !ND TO TAKE IT A STEP FURTHER IF YOUR
SERVER GIVES YOU A WAY TO TELL IT THAT
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 6
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DATABASE (ECK YOU CAN ALWAYS GO FROM THE CLIENT TO
THE DATABASE BUT THEN WERE BACK TO THE OLD NON
SCALABLE CLIENT SERVER TWO TIER ARCHITECTURE AND WE
ALL KNOW WHY THAT IS USUALLY A BAD IDEA DOESNT SCALE
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THE DATABASE YOU GET TO TAKE ADVANTAGE OF ALL THE
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SEE ONE OF THE BIGGEST BENEFITS OF USING ENTITY BEANS
IS THAT THE #ONTAINER AUTOMATICALLY SYNCHRONIZES
BETWEEN THE DATABASE AND THE ENTITY BEAN
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BEANS IS THAT THEY TAKE YOU FROM THE RELATIONAL WORLD
TO THE OBJECT WORLD )N OTHER WORDS YOU GET TO STAY
WITH OBJECTS ALL THE WAY DOWN IN YOUR APP RATHER
THAN MAPPING BACK AND FORTH IN YOUR CODE !ND IF
YOURE USING #-0 WHICH YOU ALMOST CERTAINLY WILL BE
FOR REASONS THAT WILL BECOME OBVIOUS A LITTLE LATER
YOU WONT HAVE A SHRED OF 31, IN YOUR BEAN CODE )N
FACT WITH #-0 ENTITY BEANS YOU GET TO PRETEND THAT
YOUR ENTIRE DATABASE EXISTS SOLELY AS OBJECTS ON THE
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 7
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GET A BEAN SO THAT IT CAN CALL THE BEANS BUSINESS
METHODS THE CLIENT CALLS CREATE AND THE
#ONTAINER ALLOCATES A NEW %*" OBJECT
"UT WHAT IF A CLIENT WANTS TO USE AN EXISTING ENTITY
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WANT JUST SOME RANDOM ENTITY BUT WANTS THE %*"
OBJECT OF A SPECIlC ENTITY SAY "ART 3IMPSON )N THAT CASE A CREATE WONT WORK 4HE CLIENT
DOESNT WANT A NEW ENTITY BUT WANTS A REFERENCE TO
AN EXISTING ENTITY 3O AS YOULL SEE IN A MINUTE THE
CLIENT INTERFACE FOR AN ENTITY BEAN ADDS AND MUST
HAVE ONE OR MORE lNDER METHODS
4HE NEXT TWO PAGES ARE HIGH LEVEL PICTURES OF
HOW ENTITY BEANS ARE CREATED INSERT AND FOUND
SELECT 4HE SCENARIOS IN THESE PICTURES WILL BE
lLLED IN WITH A LOT MORE DETAIL AS WE GO THROUGH
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 10
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 11
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 12
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 13
Return to Table of Contents
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 14
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 15
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 5. Entities Are Persistent
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Page 16
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
Page 20
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4HATS RIGHT BUSINESS METHODS ARENT JUST FOR THE
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
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Page 25
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 26
Return to Table of Contents
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 27
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3O WE ALL KNOW THAT AN ENTITY BEAN IS A REPRESENTATION OF
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CONFUSION ABOUT WHAT DISTINGUISHES AN ENTITY FROM AN ENTITY
BEAN FROM AN ENTITY BEAN INSTANCE
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THE BEANS HOME OR COMPONENT INTERFACE
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 28
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
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Page 29
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 30
FRIIHHFUDPPRFNH[DP
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R! 4HE QDUURZ METHOD SHOULD BE USED FOR A LOCAL HOME INTERFACE
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 31
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Page 32
Return to Table of Contents
FRIIHHFUDPPRFNH[DP
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 5. Entities Are Persistent
Return to Table of Contents
Page 33
HQWLW\EHDQLQWUR
0RFN([DP$QVZHUV
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 5. Entities Are Persistent
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 5. Entities Are Persistent
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Table of Contents
Chapter 6. Being an Entity Bean.................................................................. 1
Section 6.1. OBJECTIVES............................................................................................................................................................... 2
Section 6.2. The real power of entity beans is synchronization..................................................................................................... 4
Section 6.3. Oh no!: The entity bean and the entity it represents have different data!................................................................. 5
Section 6.4. How the entity bean and the underlying entity stay synchronized............................................................................ 7
Section 6.5. The only question is WHO does the work when it's time to synchronize.................................................................. 8
Section 6.6. Container-managed vs. bean-managed persistence.................................................................................................. 9
Section 6.7. there are no Dumb Questions................................................................................................................................... 10
Section 6.8. Off the path: A brief history on the evolution of CMP 2.0........................................................................................ 11
Section 6.9. The EntityBean interface adds three new container callbacks (including two just for synchronization)............... 16
Section 6.10. Even the methods that are the same, don't behave the same................................................................................. 17
Section 6.11. But wait... there's more! Entity beans have new home container callbacks , too................................................... 18
Section 6.12. Writing a CMP entity bean: make it abstract ......................................................................................................... 19
Section 6.13. You put three kinds of things in your bean class:................................................................................................... 20
Section 6.14. PLUS... (ok, that's four things...)............................................................................................................................. 21
Section 6.15. Virtual fields are NOT instance variables!.............................................................................................................. 22
Section 6.16. Sharpen your penil.................................................................................................................................................. 23
Section 6.17. Complete code for the CustomerBeanCMP class.................................................................................................... 24
Section 6.18. Sharpen your pencil................................................................................................................................................ 25
Section 6.19. Entity bean instance lifecycle.................................................................................................................................. 26
Section 6.20. Entity bean instance transitions............................................................................................................................. 27
Section 6.21. there are no Dumb Questions................................................................................................................................. 28
Section 6.22. Sharpen your pencil................................................................................................................................................ 29
Section 6.23. Sharpen your pencil................................................................................................................................................ 30
Section 6.24. So how DID the client get a reference to the EJB object for #28?......................................................................... 31
Section 6.25. Bean things you can do during entity construction:.............................................................................................. 33
Section 6.26. CMP Entity bean creation....................................................................................................................................... 34
Section 6.27. Creating a new entity bean: CMP entity bean........................................................................................................ 35
Section 6.28. CMP Entity bean creation....................................................................................................................................... 36
Section 6.29. Implement your ejbCreate() methods.................................................................................................................... 37
Section 6.30. Object identity: the primary key............................................................................................................................. 38
Section 6.31. Implement your ejbPostCreate() methods............................................................................................................. 40
Section 6.32. BRAIN POWER....................................................................................................................................................... 41
Section 6.33. Bean things you can do during entity creation:..................................................................................................... 44
Section 6.34. CMP Entity finder................................................................................................................................................... 45
Section 6.35. Finding an existing entity....................................................................................................................................... 46
Section 6.36. CMP Entity bean finders......................................................................................................................................... 47
Section 6.37. YOU don't implement the Finder methods!........................................................................................................... 48
Section 6.38. CMP Home Business Methods................................................................................................................................ 51
Section 6.39. Client invokes a Home Business Method............................................................................................................... 52
Section 6.40. Bean things you can do in home business methods............................................................................................... 53
Section 6.41. Starting a business method (in a transaction)........................................................................................................ 54
Section 6.42. Completing a business method (and a transaction)............................................................................................... 55
Section 6.43. Being John Entity Bean.......................................................................................................................................... 56
Section 6.44. Activation/passivation of a CMP entity bean......................................................................................................... 58
Section 6.45. Sharpen your pencil................................................................................................................................................ 59
Section 6.46. Bean things you can do during activation and loading.......................................................................................... 60
Section 6.47. Bean things you can do during passivation and storing......................................................................................... 61
Section 6.48. Commit options: what REALLY happens to a bean after a transaction commits?............................................... 62
Section 6.49. There are no Dumb Questions................................................................................................................................ 63
Section 6.50. Exercise: CMP entity bean Creation....................................................................................................................... 65
Section 6.51. Exercise: Entity Bean Business Method (with activation & passivation).............................................................. 66
Section 6.52. Exercise................................................................................................................................................................... 67
Section 6.53. COFFEE CRAM....................................................................................................................................................... 68
Section 6.54. COFFEE CRAM....................................................................................................................................................... 73
Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Page 1
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Page 4
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Page 8
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ENTITY MUST BE SYNCHRONIZED )T KNOWS BASED ON TRANSACTIONS
)F A CLIENT CALLS A METHOD ON A BEAN AND THAT METHOD STARTS A
NEW TRANSACTION FOR THE BEAN THE #ONTAINER KNOWS THAT THE
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LAST TIME THIS BEAN WAS LOADED UP WITH THIS ENTITYS DATA 3O THE
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ENTITYS DATA
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#ONTAINER WILL TELL THE DATABASE TO RELEASE THE LOCK ON THIS
ENTITY IN THE DATABASE "UT DURING THE TIME WHEN THE ROW
WAS LOCKED THE BEAN MIGHT HAVE BEEN HAPPILY CACHING DATA
THAT REPRESENTS THE NEWLY CHANGED STATE OF THE ENTITY LIKE A
NEW ADDRESS OR PHONE NUMBER )N OTHER WORDS THE CLIENT
MIGHT HAVE BEEN CALLING SETTER METHODS ON THE BEAN WITH THE
INTENTION OF CAUSING AN UPDATE IN THE REAL DATABASE 4HE CLIENT
WANTS TO UPDATE A RECORD 3O THE #ONTAINER KNOWS IT MUST
FORCE THE BEAN TO UPDATE THE DATA IN THE DATABASE WITH THE
BEANS STATE BEFORE THE #ONTAINER TELLS THE DATABASE TO RELEASE
THE LOCK ON THAT ENTITY
/+ SO THE WHEN IS NOT THE ISSUE !ND THATS IMPORTANT BECAUSE
OTHERWISE YOU THE "EAN 0ROVIDER WOULD HAVE TO WORK OUT THE
BUSINESS LOGIC TO KNOW EXACTLY WHEN THERE WAS A DANGER THAT
THE BEAN AND ENTITY ARE OUT OF SYNC !ND YOU CAN JUST IMAGINE
HOW QUICKLY YOU COULD CORRUPT THE STATE OF YOUR DATABASE
4HE REAL ISSUE IS WHO DOES THE DATABASE ACCESS !ND THERE ARE
ONLY TWO CHOICES ITS EITHER YOU OR THE #ONTAINER
)F YOU WRITE THE DATABASE ACCESS CODE YOU WRITE *$"#
STATEMENTS IN THE CALLBACK METHODS THE #ONTAINER CALLS WHEN
ITS TIME TO KICK YOU AND SAY h(EY TIME TO GO TO THE DATABASEv
/N THE OTHER HAND IF THE #ONTAINER WRITES THE DATABASE CODE
YOU SAVE YOURSELF A LOT OF CODING TIME AND EFFORT AND YOULL
ALMOST ALWAYS GET BETTER PERFORMANCE
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 10
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YOU DO BEAN MANAGED PERSISTENCE
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TABASE ACCESS IS NOT JUST FOR ENTITY BEANS
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OF ITS BUSINESS LOGIC 3ESSION BEANS AND
MESSAGE DRIVEN BEANS MIGHT FIND PLENTY
OF REASONS TO LOOK SOMETHING UP OR STORE
SOMETHING IN A DATABASE 4HE DIFFERENCE
BETWEEN ENTITY BEANS AND THE OTHER TWO
BEAN TYPES IS THAT ENTITY BEANS EXIST ONLY
BECAUSE THERES SOMETHING IN A DATA
BASE 3OMETHING THE BEAN REPRESENTS
3O ENTITY BEANS ARE BY DEFINITION TIED TO
SOMETHING IN A PERSISTENT STORE
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BE BETTERˆNOT WORSEˆWITH "-0
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!ND ACCORDING TO NEARLY ALL BENCHMARKS
AGAINST THE MAJOR *%% SERVERS NOT
BETTER PERFORMANCE 4HAT MIGHT SOUND
COUNTERINTUITIVE BUT REMEMBER THAT THE
#ONTAINER CAN DO THINGS THAT YOU CANT
DO FROM WITHIN BEAN CODE 4HINGS LIKE
GANGING MULTIPLE CALLS TO THE DATABASE
USING NATIVE CODE TO GET IN AN OUT OF
THE DATABASE FASTER THAN YOU COULD LAZY
LOADING DIRTY DETECTION NEITHER OF WHICH
ARE GUARANTEED BY THE SPEC OF COURSE
AND DOZENS OF OTHER TRICKS
7E KNOW IT GOES AGAINST THE
CONVENTIONAL WISDOM THAT SAYS IF YOU
WANT IT DONE RIGHT DO IT YOURSELF BUT
KEEP IN MIND THAT THE SERVER VENDORS ARE
COMPETING FOR YOUR BUSINESS 4HEY KNOW
PERFORMANCE MATTERS TO YOU 4HE SPEC ADDEDˆAND CHANGEDˆA LOT OF THE
#-0 SPECIFICATION FOR THE SOLE PURPOSE
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Page 11
Return to Table of Contents
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THE HIGHEST LEVEL THE DIFFERENCE BETWEEN #-0 AND "-0 IS ABOUT WHO
WRITES THE DATABASE ACCESS CODE
7ITH %*" YOU CAN STILL USE BOTH BUT THERES NOW VERY LITTLE REASON
TO EVER USE "-0 4HE ORIGINAL %*" SPECIlCATION FOR #-0 ENTITY
BEANS WAS UM WEAK #LUNKY )NEFlCIENT ,IMITED .OT 4HAT 'OOD !ND
ALTHOUGH MANY VENDORS WERE ABLE TO OVERCOME MANY OF THE PROBLEMS
WITH #-0 THE SOLUTIONS WERE OUTSIDE THE SPECIlCATION SO YOUR CHOICE
AS BEAN DEVELOPER WAS TO USE STANDARD #-0 BUT KEEP YOUR PORTABILITY
OR STEP OUTSIDE THE SPEC REDUCING YOUR PORTABILITY BUT GET BETTER
PERFORMANCE AND FEATURES
7HEN THE %*" SPEC WAS CREATED THE TEAM SPENT A GREAT DEAL OF TIME
AND EFFORT TALKING TO BOTH END USER CUSTOMERS BEAN DEVELOPERS AND
CONTAINER VENDORS ALL OF WHOM WERE VERY HAPPY TO DESCRIBE THE PROBLEMS
WITH #-0 )N GRAPHIC DETAIL COMPLETE WITH SUGGESTIONS FOR 3UN ON h)LL
TELL YOU WHAT YOU CAN $/ WITH YOUR #-0 BEAN SPECv
4HE %*" SPEC TEAM LISTENED !ND DESIGNED !ND LISTENED !ND DESIGNED
!ND IN THE END THEY CAME UP WITH SOMETHING AWFUL ! SOLUTION THAT WAS
AN EQUAL OPPORTUNITY PISSER OFFER 6ENDORS HATED IT $EVELOPERS HATED IT
0EOPLE LIKE US WHO HAD TO EXPLAIN THE NEW TECHNOLOGY TO CUSTOMERS REALLY
HATED IT 3O WITH THE DEADLINE UPON THEM THE TEAM SCRAPPED MUCH OF
WHAT THEYD DONE WITH #-0 AND CAME UP WITH A MUCH CLEANER SOLUTION
7ITH THE NEW %*" SPEC #-0 IS LIGHTYEARS AHEAD OF WHERE IT WAS IN %*"
OR IN THE lRST TERRIBLE VERSION OF THE PRE RELEASE %*" SPEC !ND
NOW MOST DEVELOPERS USING ENTITY BEANS WILL USE #-0 )N FACT THE EXAM
DOESNT COVER "-0 AT ALL SINCE ITS THERE MORE FOR LEGACY SUPPORT OR VERY
SPECIAL CASES MORE THAN ANYTHING ELSE
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WONT COVER "-0 IN THIS BOOK 3O FROM THIS POINT FORWARD WERE GOING
TO ASSUME THAT WERE TALKING ABOUT #-0 4HE DIFFERENCES BETWEEN
THE LIFECYCLE AND THE DEVELOPERS RESPONSIBILITY FOR #-0 VS "-0 ARE
DRAMATIC SO DONT FORGET THAT EVERYTHING WE TALK ABOUT NOW WILL BE FROM
THE PERSPECTIVE OF A #-0 BEAN EVEN IF WE DONT EXPLICITLY SAY THAT WERE
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 12
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 13
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 16
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 17
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 18
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 19
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 20
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 21
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 22
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 23
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 24
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 25
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 26
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 27
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 28
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Page 29
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THAN YOU NEED TO ACCESS THOSE RESOURCES
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 30
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 31
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 32
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 35
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 38
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Page 39
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Page 40
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 46
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 59
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 60
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&KDSWHU
Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 61
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\RXDUHKHUH
Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 62
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 63
HQWLW\EHDQV\QFKURQL]DWLRQ
there are no
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Q:
(OW DOES THESE COMMIT
OPTIONS AFFECT ME $O ) NEED TO
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THE %*" OBJECT !RENT POOLS MORE
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IN PROGRESS METHODS
A:
A:
!CCORDING TO THE SPECIFICATION
YOUR VENDOR IS FREE TO USE ANY OF THE
THREE OPTIONS 9OUR CONTAINER MIGHT LET
YOU CHOOSE OR TUNE THE OPTION BUT
DONT ALWAYS COUNT ON IT "UT DO YOU
NEED TO KNOW WHICH IS BEING USED
9OU CAN SEE WHERE THE TRADE OFFS ARE
OF COURSEˆIF YOU KEEP THE ENTITY
LOCKED IN THE DATABASE NO OTHER
APPLICATIONS CAN USE THAT ENTITYS
DATA 4HATS FINE IF THE %*" IS THE ONLY
APPLICATION THAT NEEDS THAT DATABASE
!ND THAT OPTION COMMIT OPTION
! GIVES YOU THE BEST PERFORMANCE
WHEN A BUSINESS METHOD CALL COMES
IN FOR THE ENTITY BECAUSE THERES
NO EJB!CTIVATE THE BEAN NEVER
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SIGNIFICANTLYˆTHERES NO TRIP TO THE
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A:
&OR THIS REASON MOST VENDORS
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SUPPORTED AT ALL Q:
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!H NOW WE COME TO THE
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IMPLEMENT THINGS
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WHEN THE CLIENT GETS A STUB TO AN
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THE STUB KNOWS THE UNIQUE )$ FOR
THE ENTITY IE THE PRIMARY KEY "UT
THE %*" OBJECTS MIGHT BE GENERIC
IN SUCH A WAY THAT WHEN THE CLIENT
CALLS A METHOD ON A STUB THAT STUB IS
CONNECTED NOT TO AN %*" OBJECT JUST
FOR THAT ENTITY BUT RATHER A ONE %*"
OBJECT FITS ALL THAT KNOWS HOW TO MAKE
SURE THE METHOD ENDS UP AT THE RIGHT
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USING AN %*" OBJECT THAT %*" OBJECT
ISNT SITTING AROUND WASTING SPACE
4HATS JUST ONE IDEA
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BUT WHAT IF THE CLIENT IS LOCAL 4HEN
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\RXDUHKHUH
Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 64
FRPPLWRSWLRQV
there are no
Dumb Questions
Q:
7HICH OF THE THREE COMMIT
OPTIONS DO YOU THINK IS MOST USED
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OUR MONEY WOULD BE ON OPTION " !
@SMART OPTION " THAT KNOWS WHEN IT
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AND WHEN IT DOESNT "UT AVOIDING THE
EJB!CTIVATE WHICH IS USUALLY USELESS
ANYWAY IS A 'OOD 4HING
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"UT ISNT THE HIT TO THE
DATABASEˆTHE LOADˆA MUCH BIGGER
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ON THE STACK
A:
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PROBABLY A LITTLE MORE THAN JUST
ONE MORE METHOD CALL ON THE STACK
BECAUSE THERES OVERHEAD JUST IN
MAINTAINING THE ORGANIZATION OF THE
POOL ITSELF "UT YES YOURE RIGHT ABOUT
THE DATABASE HIT BEING A BIGGER DEAL
"UT THERES ALL SORTS OF WAYS THE
#ONTAINER CAN OPTIMIZE AND WHATS
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STILL DANGEROUS BECAUSE ENTITIES ARE
PERSISTENT 3O THE VENDOR STILL MUST
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SERVER WILL HAVE TO BE CERTAIN THAT ALL
INSTANCES OF THAT ENTITY BEAN IN SYNC
NOT JUST WITH THE DATABASE BUT WITH
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PERFORMANCE CHAPTER
Q:
3O IS THE REAL POINT OF ALL THIS
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TRANSACTION YOU WONT HAVE ALL THESE
LOADSTORE ACTIVATEPASSIVATE CALLS
A:
9ES A BIG PART OF THE POINT
ANYWAY
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YOURE DOING MORE LOADSSTORES THAN
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TRANSACTIONS BE AS LONG AS YOU NEED
AND NO LONGER
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LIKELY IT IS THAT OTHERS ARE WAITING IN
LINE TO GET TO THAT ENTITY /F COURSE
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WHICH ARE TOO SHORT WHICH MEANS
&KDSWHU
Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 65
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 70
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Page 72
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 74
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 6. Being an Entity Bean
Return to Table of Contents
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 6. Being an Entity Bean
Return to Table of Contents
Page 76
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 6. Being an Entity Bean
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
Table of Contents
Chapter 7. When Beans Relate.................................................................... 2
Section 7.1. OBJECTIVES: Entity Relationships: CMP and CMR................................................................................................. 3
Section 7.2. Beanifying your movie database................................................................................................................................. 4
Section 7.3. But we don't want to think in TABLES We want to think in CLASSES..................................................................... 5
Section 7.4. We need relationships between the Movie bean and the Director............................................................................. 7
Section 7.5. Why should the Director be a bean? Why can't it just be data?................................................................................. 8
Section 7.6. Relationships and multiplicity.................................................................................................................................... 9
Section 7.7. Multiplicity in Bean Classes...................................................................................................................................... 10
Section 7.8. Multiplicity affects return type !................................................................................................................................ 11
Section 7.9. You need a pair of abstract getters and setters for each CMP field (column values) and each CMR field (relationship
with another entity)....................................................................................................................................................................... 12
Section 7.10. Defining your "abstract persistence schema" (virtual fields aren't enough).......................................................... 13
Section 7.11. The Container needs these TWO things to know you have a CMP field "title"....................................................... 13
Section 7.12. Persistent CMP fields in the DD.............................................................................................................................. 14
Section 7.13. there are no Dumb Questions.................................................................................................................................. 14
Section 7.14. Using relationships in your code............................................................................................................................. 15
Section 7.15. Defining relationships in your abstract persistence schema (in the DD)............................................................... 16
Section 7.16. Relationship definition for the Director-to-Movie relationship............................................................................. 17
Section 7.17. Sharpen your pencil................................................................................................................................................. 19
Section 7.18. Director-to-Movie relationship............................................................................................................................... 19
Section 7.19. Relationships can be one-way ( unidirectional)..................................................................................................... 20
Section 7.20. The dark side of a unidirectional (one-way) relationship...................................................................................... 21
Section 7.21. Cascade delete can propagate.................................................................................................................................. 22
Section 7.22. Director-to-Movie relationship............................................................................................................................... 22
Section 7.23. Movie-to-Trailer relationship................................................................................................................................. 22
Section 7.24. The abstract schema> element is in the <entity> element and the <ejb-relation> is in the <relationships.....
23
Section 7.25. MovieBean with a CMR code field.......................................................................................................................... 25
Section 7.26. The MovieBean's home interface............................................................................................................................ 27
Section 7.27. Mapping from abstract schema to a real database................................................................................................. 29
Section 7.28. Writing your portable queries, for select and finder methods............................................................................... 30
Section 7.29. EJB-QL for the MovieBean..................................................................................................................................... 31
Section 7.30. Using an optional WHERE clause.......................................................................................................................... 32
Section 7.31. Navigating to another related bean......................................................................................................................... 33
Section 7.32. Selecting a value rather than the whole bean......................................................................................................... 34
Section 7.33. EJB-QL SELECT..................................................................................................................................................... 35
Section 7.34. EJB-QL SELECT—when to use Object ()............................................................................................................... 36
Section 7.35. Sharpen your pencil................................................................................................................................................ 36
Section 7.36. What does it MEAN to return an abstract schema type?....................................................................................... 37
Section 7.37. SELECT and FROM are mandatory !..................................................................................................................... 38
Section 7.38. Identifiers................................................................................................................................................................ 39
Section 7.39. The WHERE clause................................................................................................................................................. 40
Section 7.40. The WHERE clause................................................................................................................................................. 41
Section 7.41. The problem with using Collection types................................................................................................................ 42
Section 7.42. Collections don't bark() !........................................................................................................................................ 43
Section 7.43. The IN operator lets you say "For an individual element IN the Collection..."..................................................... 44
Section 7.44. The BETWEEN expression..................................................................................................................................... 45
Section 7.45. The other "IN"......................................................................................................................................................... 46
Section 7.46. The IS EMPTY comparison expression.................................................................................................................. 47
Section 7.47. The IS NOT EMPTY comparison expression.......................................................................................................... 47
Section 7.48. The LIKE expression............................................................................................................................................... 48
Section 7.49. The NOT LIKE expression...................................................................................................................................... 49
Section 7.50. Relationship assignments........................................................................................................................................ 51
Section 7.51. If the multiplicity of the relationship field is ONE, it's a MOVE If the multiplicity is MANY, it's a COPY........... 52
Section 7.52. Exercise: Multiplicity and Assignments................................................................................................................. 52
Section 7.53. Solution: Multiplicity and Assignments................................................................................................................. 53
Section 7.54. COFFEE CRAM....................................................................................................................................................... 54
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 7. When Beans Relate
Section 7.55. COFFEE CRAM....................................................................................................................................................... 60
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Page 8
Return to Table of Contents
HQWLW\EHDQUHODWLRQVKLSV
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7HY NOT HAVE THE -OVIE BEAN SIMPLY GO TO THE DATABASE
USING THE $IRECTORS FOREIGN KEY STORED AS A PERSISTENT
lELD IN THE -OVIE BEAN AND GET THE $IRECTORS DATA "UT
IF YOU MAKE THE DIRECTOR A BEAN AS WELL YOU GET TO THINK
/.,9 IN OBJECTS EXCEPT DURING DEPLOYMENT WHEN YOU
DO HAVE TO MAP FROM YOUR BEANS TO YOUR TABLES !ND YOU
GET ALL THE BENElTS OF CONTAINER MANAGED PERSISTENCE AND
SYNCHRONIZATION )MAGINE IF SOMEONE CALLS A SETTER METHOD
TO CHANGE THE DIRECTORS OSCAR WINNING STATUS )F YOURE
MANAGING THIS YOUD HAVE TO GET A *$"# CONNECTION AND
SYNCHRONIZE THE DATABASE YOURSELF !ND OF COURSE YOUD HAVE
TO KNOW WHEN IS THE RIGHT TIME ETC "UT IF ITS DIRECTOR IS ALSO A
BEAN YOU CALL A SET7INNER METHOD AND YOURE DONE
/H AND THERES ANOTHER COOL THING 9OU MIGHT DECIDE FOR
EXAMPLE TO BANISH A SPECIlC DIRECTOR FROM YOUR DATABASE
BECAUSE YOU THINK HIS MOVIES SUCK IN AN UNRECOVERABLE WAY
.O PROBLEM DELETING THAT DIRECTOR OBVIOUSLY "UT THEN WHAT
HAPPENS TO THE MOVIES (OW CAN YOU HAVE MOVIES IN THE
DATABASE THAT DONT HAVE A DIRECTOR 7HAT IS THE DATABASE IS
ALREADY SET UP IN SUCH A WAY THAT YOU ARENT ALLOWED TO HAVE A
NULL VALUE FOR THE DIRECTOR COLUMN )N OTHER WORDS WHAT IF A
MOVIE CANNOT EXIST IN THE DATABASE WITHOUT A DIRECTOR
9OU CAN HANDLE THIS BRAINLESSLY BY SETTING UP THE -OVIE
TO $IRECTOR BEAN RELATIONSHIP IN SUCH A WAY THAT WHEN YOU
DELETE A DIRECTOR FROM THE DATABASE ALL OF HIS MOVIES ARE
AUTOMATICALLY DELETED 9OU DO THIS WITH ONE SIMPLE TAG IN THE
DEPLOYMENT DESCRIPTOR AND 0//& 3OMEBODY CALLS REMOVE
ON A DIRECTOR BEAN AND REMOVE WILL AUTOMATICALLY BE CALLED
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 9
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 10
HQWLW\EHDQUHODWLRQVKLSV
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(ERES HOW IT WORKS WITH OUR BEAN CODE 4HIS MULTIPLICITY NOTATION
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THE 0ERSON TO 0ETS RELATIONSHIP 0ERSON HAS A MULTIPLICITY OF /.%
BUT 0ETS HAS A MULTIPLICITY OF -!.9 WHICH COULD BE ZERO 4O
lND OUT HOW MANY 0ETS A 0ERSON CAN HAVE YOU HAVE TO FOLLOW
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 11
UHODWLRQVKLSPXOWLSOLFLW\
5]T\QXTQKQ\aINNMK\[ZM\]ZV\aXM
! -OVIE HAS ONE $IRECTOR 7HEN YOU CALL GET$IRECTOR YOU
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A $IRECTOR "UT A $IRECTOR HAS MANY MOVIES SO WHEN YOU CALL
GET-OVIES YOU GET BACK A #OLLECTION OF -OVIES
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)N THE -OVIE TO $IRECTOR RELATIONSHIP THE MULTIPLICITY OF
-OVIE IS MANY AND THE MULTIPLICITY OF $IRECTOR IS ONE
Movie has a multiplicity of
ÒmanyÓ in its relationship with
Director. That does NOT
mean that Movie has ÒmanyÓ
Directors... it means that
Director has ÒmanyÓ Movies!
So Director has a getMovies()
that returns a Collection of
Movies.
And Director has a multiplicity
of ÒoneÓ, which means that
Movie will return just one
Director.
! MULTIPLICITY OF ONE MEANS THE OBJECT YOURE RELATED TO
HOLDS JUST ONE OF YOU
$IRECTOR HAS A MULTIPLICITY OF ONE SO THE -OVIE OBJECT RELATED
TO $IRECTOR RETURNS JUST A SINGLE $IRECTOR BEAN /+ TECHNICALLY
THE COMPONENT INTERFACE OF $IRECTOR BUT YOU KNOW WHAT WE
MEAN BY NOW ! MULTIPLICITY OF MANY MEANS THE OBJECT YOURE RELATED TO
HOLDS A #OLLECTION OF YOU
-OVIE HAS A MULTIPLICITY OF MANY SO THE $IRECTOR OBJECT
RELATED TO -OVIE RETURNS A #OLLECTION OF -OVIE BEANS
&KDSWHU
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 12
HQWLW\EHDQUHODWLRQVKLSV
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lELDSˆYOU PUT IN A PAIR OF ABSTRACT GETTERS AND SETTERS 7E SAID A
CONTAINER MANAGED lELD EXISTS SIMPLY BECAUSE YOU HAVE A GETTER AND SETTER FOR
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lELDS 9OU DElNE A PAIR OF ABSTRACT GETTERS AND SETTERS BUT RATHER THAN
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HOLD REFERENCES TO THE ENTITY BEAN 4HE RESTRICTIONS FOR #-2 lELDS ARE
THAT THEY CAN REFER ONLY TO THE LOCAL COMPONENT INTERFACE OF THE ENTITY
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CALLED IT #-0#$ CONTAINER MANAGED PERSISTENT COLUMN DATA lELDS
AND #-02 CONTAINER MANAGED PERSISTENT RELATIONSHIP lELDS /F
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USING THE TERM hCOLUMNv A LITTLE LOOSELY "UT IN %*" ALL CONTAINER
MANAGED PERSISTENT lELDS WERE #-0 lELDS BECAUSE THERE WAS NO
CONCEPT OF PERSISTENT RELATIONSHIPS IN %*" #-0
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 13
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STRAIGHTFORWARD 7ITH #-2 YOULL HAVE TO DO A LITTLE MORE
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 14
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 15
HQWLW\EHDQUHODWLRQVKLSV
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BETWEEN USING A REAL lELD IE AN INSTANCE VARIABLE DECLARED IN
YOUR CLASS AND A VIRTUAL lELD IS THAT YOU CAN ACCESS YOUR VIRTUAL
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 16
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IT A NAME THAT MATCHES ONE OF YOUR GETTERSETTER PAIRS FOLLOWING THE
NAMING RULE OF DROPPING THE hGETv AND hSETv AND BEGINNING THE #-0
lELD NAME WITH A LOWER CASE LETTER "UT #-2 IS MORE INVOLVED 9OU CANT BE IN A RELATIONSHIP WITH ONLY
YOURSELF SO A RELATIONSHIP ALWAYS INCLUDES TWO BEANS
ionship has
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when its partner is delnts
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 17
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e named this <ejb-relations
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This is a made-up name! ItÕs
choose to call the ROLE. simply what you
We could have called
it ÒDirectorRoleÓ or any
thi
participant weÕre talking ng that tells us which
about.
Remember, this does NOT say how many
participant the Director bean will have of the other
... it says how
many of THIS bean the OTHER part
Movie will have only ONE Director. ner will have.
UHODWLRQVKLSUROHVRXUFH!
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EXACTLY which bean weÕre talking about.
Put the beanÕs <ejb-name> which is just a
label telling the Container where to Þnd
this beanÕs real deÞnition in the <enterprisebeans> section of the DD. This MUST
match an <ejb-name> in the DD.
FPUÀHOGIRUWKLVEHDQ
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FPU¿HOGQDPH!PRYLHVFPU¿HOGQDPH!
This must match a Òvirtual ÞeldÓ in the
bean class for getMovies() / setMovies
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to this
bean, which means you will hold more
one, so you need a Collection. You canthan
say java.util.Set (your only two choices)also
&KDSWHU
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 18
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Remember, this is just a name for
your own (or the App Assembler or a
toolÕs) use. It means nothing in your
Java code.
This means Director will have MANY of
type (Movie). Se we expect that Directorthis
have a CMR Þeld with a Collection type will
rather
than a single Movie
This MUST match the <ejb-name> for
where you deÞned the Movie entity
bean in the <enterprise-beans> section
of the DD.
FPUÀHOGIRUWKLVEHDQ
FPU¿HOG!
FPU¿HOGQDPH!GLUHFWRUFPU¿HOGQDPH!
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nÕt have a
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e>
yp
<cmr-Þeld-t
, the only reason
Collection. In facteld
-type> tag is
-Þ
mr
<c
thereÕs a
pe is a Colty
ld
Þe
for when the
to distinguish
lection, and you havellection. <cmrCo
or
t
between Se
Þeld-type>
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bean to be deleted whenever its
partner is deleted.
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 19
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 20
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9OU CAN HAVE A RELATIONSHIP BETWEEN TWO
BEANS BUT HAVE A #-2 lELD IN ONLY ONE OF
THE TWO BEANS &OR EXAMPLE IF YOU SET UP A
RELATIONSHIP BETWEEN A -OVIE AND ITS 4RAILER
A ONE TO ONE RELATIONSHIP AND YOU DONT
WANT CLIENTS TO USE A 4RAILER TO GET TO A -OVIE
JUST LEAVE THE #-2 lELD FOR -OVIE OUT OF THE
4RAILER BEAN 3IMPLE AS THAT
)N THAT CASE THE 4RAILER"EAN WONT KNOW
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 21
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 22
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Page 23
Return to Table of Contents
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 24
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 25
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wait until WE have eate() completes.
only AFTER ejbCr
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 26
HQWLW\EHDQUHODWLRQVKLSV
SXEOLF6WULQJHME+RPH/LVW$OO0RYLHV ^
6WULQJOLVW QXOO
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ess method
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`
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UHWXUQJHW'LUHFWRU JHW'LUHFWRU1DPH `
SXEOLFDEVWUDFW6WULQJJHW0RYLH,' SXEOLFDEVWUDFWYRLGVHW0RYLH,' 6WULQJL SXEOLFDEVWUDFW6WULQJJHW7LWOH SXEOLFDEVWUDFWYRLGVHW7LWOH 6WULQJW SXEOLFDEVWUDFWLQWJHW<HDU SXEOLFDEVWUDFWYRLGVHW<HDU LQW\ SXEOLFDEVWUDFW6WULQJJHW*HQUH SXEOLFDEVWUDFWYRLGVHW*HQUH 6WULQJJ SXEOLFDEVWUDFW'LUHFWRUJHW'LUHFWRU SXEOLFDEVWUDFWYRLGVHW'LUHFWRU 'LUHFWRUG We have FIVE virtual Þelds:
four CMP Þelds and
one CMR Þeld for Director.
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WKURZV)LQGHU([FHSWLRQ
SXEOLFDEVWUDFW&ROOHFWLRQHME6HOHFW*HW0RYLHV%\'LUHFWRU$QG*HQUH 6WULQJGLU6WULQJ
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SXEOLFYRLGHME/RDG ^`
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SXEOLFYRLGHME3DVVLYDWH ^`
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^`
The two select methods are declared as
abstract methods. The Collection doesnÕt say
WHAT the methods will return... but weÕll tell
the Container that one will return a Collection
of Movies and one a Collection of Strings.
SXEOLFYRLGVHW(QWLW\&RQWH[W (QWLW\&RQWH[WFW[ ^
FRQWH[W FW[
`
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regular old callback
methods.
\RXDUHKHUH
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Page 27
Return to Table of Contents
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SXEOLF0RYLH5HPRWHFUHDWH 6WULQJPRYLH,'6WULQJWLWOHLQW\HDU6WULQJJHQUH
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rs
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the home.
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er HOW to implement th
Þnders, which brings us
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 28
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 29
GDWDEDVHWRHQWLW\PDSSLQJ
5IXXQVONZWUIJ[\ZIK\[KPMUI\WIZMITLI\IJI[M
3OONER OR LATER YOU HAVE TO TELL THE #ONTAINER HOW AND WHERE TO MANAGE YOUR
PERSISTENT DATA 4HIS HAPPENS OUTSIDE THE DEPLOYMENT DESCRIPTOR IN A VENDOR
SPECIlC WAY 4HAT MEANS OF COURSE THAT YOURE NOT TESTED ON IT IN THE EXAM %VERY
VENDOR HAS THEIR OWN MECHANISM BUT YOULL USUALLY GET SOME SORT OF A '5) WHERE
IF YOURE LUCKY YOU CAN TELL THE #ONTAINER TO CONNECT TO A SPECIlC DATABASE AND
THEN YOULL DRAG AND DROP OR DRAW CONNECTIONS FROM #-0 lELDS TO COLUMNS IN
ONE OR MORE TABLES
"ECAUSE THIS MAPPING HAPPENS OUTSIDE OF %*" IN THE SERVER THERES NOT MUCH
WE CAN SAY ABOUT IT 4HE PART WERE MOST INTERESTED IN IS MAPPING FROM ABSTRACT
QUERIES TO 2%!, QUERIES AND THAT HAPPENS IN A VERY COOL WAY USING A VENDOR
INDEPENDENT QUERY LANGUAGE JUST FOR YOUR ENTITY BEAN QUERIES %*" 1, 7ELL LOOK
AT THAT ON THE NEXT PAGE
DEVWUDFWVFKHPDQDPH!0RYLH6FKHPDDEVWUDFWVFKHPDQDPH!
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Notice that weÕre not
ma
column (the one that ke pping the Director ID
ep
the Director table) be s the foreign key into
cause we donÕt HAVE a
persistent CMP Þeld fo
r
that, when we can have the Director ID. Why do
the real Director, as an
entity bean, instead? Th
at
comes in, but we donÕt Õs where our CMR Þeld
map that to a database.
Relationships happen by
ma
the <relationships> part tching up two BEANS in
of the DD.
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 30
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%*" 1, IS A PORTABLE QUERY LANGUAGE THAT LETS YOU
WRITE 31, LIKE STATEMENTS WRITE INTO THE DEPLOYMENT
DESCRIPTOR 9OU PUT THEM IN THE 8-, AND WITHOUT
HAVING TO KNOW ANYTHING ABOUT THE REAL DATABASE
!S A "EAN 0ROVIDER YOU CAN HAPPILY WRITE ALL THE
QUERIES YOU WANT TRUSTING THAT THE $EPLOYER WILL IN THE
END MAP YOUR #-0 lELDS TO REAL TABLES AND DATA !LL
WE CARE ABOUT HERE IS WRITING OUR QUERIES TO MATCH THE
METHODS WEVE CHOSEN TO EXPOSE TO THE CLIENT IN THE
HOME AND COMPONENT INTERFACES
3ELECT METHODS ARE HERE SIMPLY TO MAKE YOUR LIFE
EASIER BY LETTING THE #ONTAINER BUILD THE REAL DATABASE
ACCESS CODE FROM YOUR QUERIES
3O THE PROCESS IS USUALLY SOMETHING LIKE
7RITE A HOME BUSINESS METHOD
)MPLEMENT THE HOME BUSINESS METHOD TO CALL
THE EJB3ELECT METHOD THAT DOES THE REAL DATA ACCESS
$ECLARE THE ABSTRACT SELECT METHOD IN YOUR BEAN
CLASS
7RITE THE %*" 1, FOR THE SELECT QUERY
\RXDUHKHUH
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
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Page 31
(-%4/TXHULHV
-2*94NWZ\PM5W^QM*MIV
,ETS LOOK AT THE %*" 1, FOR ALL THE QUERIES THE -OVIE"EAN NEEDS $ONT WORRY IF YOURE
NOT UNDERSTANDING ALL OF IT AFTER WE WALK THROUGH THE EXAMPLES WELL EXPLORE THE
DIFFERENT PIECES IN DETAIL AND WORK OUT THE SYNTAX )F YOU KNOW 31, MOST OF THIS WILL BE
FAMILIAR ALTHOUGH THERE ARE FEW DIFFERENCES YOULL SEE )F YOU DONT KNOW 31, THATS
/+ 7ELL GET YOU STARTED WRITING QUERIES AND YOU CAN USE THE SPEC TO LEARN MORE ABOUT
THE %*" 1, LANGUAGE 4HE EXAM EXPECTS YOU TO KNOW JUST THE BASICS OF %*" 1,
,QWKHEHDQFODVV
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M
Collection of
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This says ÒReturn what
eve
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am
to represent MovieSch ple, ÔmÕ is said
ema which really
means the Movie entit
y be
Þrst part says, ÒGive me an type. So this
Movie beansÓ.
... ÒLet ÔmÕ
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ca
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&KDSWHU
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 32
HQWLW\EHDQUHODWLRQVKLSV
=[QVOIVWX\QWVIT?0-:-KTI][M
4HIS EXAMPLE CONSTRAINS THE OBJECTS RETURNED FROM THE SEARCH BY ADDING A 7(%2%
CLAUSE THAT SAYS WHAT EXTRA CRITERIA THE OBJECTS HAVE TO MEET BEFORE THEY QUALIFY FOR
hTHINGS THAT CAN BE RETURNED FROM THE QUERYv 4HE 7(%2% CLAUSE IS YOUR WAY OF
SAYING h$ONT JUST GIVE ME !.9 OLD -OVIE ) WANT /.,9 THE MOVIES THATv
,QWKHEHDQFODVV
turns a
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Collectio
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the
CMP Þeld in
ÒgenreÓ must behich means you can
Movie bean, w re() / setGenre()
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method pair in
this means the
Þrst parameter
to the method
the
This says we want the
t
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ly
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to on
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pe
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rns
Movie bean ty
restrict the M CMP Þeld ÒgenreÓ
out to be...
e
those where th t parameter of the
rs
Þ
matches the he Ò1Ó means the Þrst
T
d
select metho Òm.genreÓ uses the dot
he
T
parameter.
a ÒpathÓ
ator to make iented
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on
ti
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vi
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in an object-or
that navigates the left hand operand
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an
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ing regular Jav
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\RXDUHKHUH
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 33
SDWKQDYLJDWLRQ
6I^QOI\QVO\WIVW\PMZZMTI\MLJMIV
4HIS EXAMPLE IS FOR A lNDER METHOD SO YOU WONT lND IT IN THE BEAN CLASS
REMEMBER YOU DECLARE ABSTRACT METHODS FOR ONLY THE SELECT METHODS NOT THE
lNDERS 4HE #ONTAINER USES YOUR HOME INTERFACE TO lGURE OUT WHAT THE lNDERS ARE
AND THEN ITS UP TO YOU TO WRITE THE %*" 1, FOR THE lNDERS 9OU CAN USE THE DOT OPERATOR TO NAVIGATE NOT JUST TO A #-0 lELD IN THE BEAN BUT TO
ANOTHER lELD WITHIN A BEAN REFERENCED IN A #-2 lELD )N OTHER WORDS )F -OVIE HAS A
REFERENCE TO A $IRECTOR AND THEYRE IN A RELATIONSHIP YOU CAN USE THE -OVIE TO GET
TO THE $IRECTOR TO ASK FOR A #-0 VALUE FROM THE $IRECTOR
,QWKHKRPHLQWHUIDFH
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ns Òthe
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the Movie bean
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the Directoreld in
bean.
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This says that we want
objects returned wh
type
is whatever ÔmÕ turnsose
ou
t
to
be representing...
o you know?
... and what dthat ÔmÕ
t
It turns ou ovie bean
means the M
restrict the Movies returned to only those
where the MovieÕs Director has a CMP
ÒdegreesÓ Þeld with a value that matches
the Þrst parameter of the Þnder.
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 34
HQWLW\EHDQUHODWLRQVKLSV
;MTMK\QVOI^IT]MZI\PMZ\PIV\PM_PWTMJMIV
4HIS EXAMPLE IS FOR A HOME BUSINESS METHOD THAT TAKES TWO PARAMETERS
AND RETURNS NOT -OVIES BUT 3TRINGS
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ng, with all
rns a single Stri query.
tu
re
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that match the
the Movie titles
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this is different! WeÕre returning just
Movie titles, not Movie objects
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the ÒgenreÓ
m.genre means the Movie bean
in
CMP Þeld
:+(5(PGLUHFWRUGLUHFWRU,' "$1'PJHQUH "
This restricts the matc
Movies with a Director hes to only those
equal to the Þrst para who has an ID
meter to the
method
AND whose Movie genre value equals the
second parameter to the method
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 35
(-%4/6(/(&7
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.OW THAT YOUVE SEEN SOME QUERIES WELL LOOK AT SOME OF THE DETAILS AND RULES
4XHU\'RPDLQV
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JAR lLE (OWEVER MANY BEANS YOU CAN SQUISH IN THE EJB JAR THATS HOW MANY BEANS YOU
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terms (and in
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the spec) the ECT variable
type as a SELNGE variable,
25
is called a RA es over the
because it rangbean type.
entire entity
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weÕre using the schema name and not,
say, the bean name. In the spec, the
abstract schema name is the same
as the component interface name.
&KDSWHU
Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 36
HQWLW\EHDQUHODWLRQVKLSV
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#-0 lELD TYPE
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 37
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 38
HQWLW\EHDQUHODWLRQVKLSV
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9OU GOTTA HAVE 3%,%#4 AND &2/- NO MATTER WHAT BUT THE 7(%2%
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TO SAY THAT YOU DONT WANT ANY DUPLICATES RETURNED IN YOUR #OLLECTION
use it
declare it
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#ONTAINER h(ERES WHERE ) WANT YOU TO BE LOOKINGv 4HE ORDER IN WHICH THE
&2/- AND 3%,%#4 MIGHT FEEL A LITTLE STRANGE IF YOURE NOT USED TO 31, "UT
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)M TALKING ABOUT ARE &2/- MY TOP DRAWERv
)F YOU NEED TO DECLARE MORE IDENTIlCATION VARIABLES TO USE LATER IN THE QUERY
YOU CAN SEPARATE THEM WITH A COMMA
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and deÞned the domain identiÞers,
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 39
(-%4/LGHQWL¿HUV
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7HEN YOU MAKE AN IDENTIlER YOU HAVE TO FOLLOW THE *AVA
PROGRAMMING LANGUAGE GUIDELINES FOR WHAT YOU CAN NAME THINGS
9OU CANT USE THE OTHER *AVA IDENTIlERS
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 40
HQWLW\EHDQUHODWLRQVKLSV
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RETURNED 2EMEMBER THAT WITHOUT ONE WE GOT EVERYTHING OF THE TYPE USED
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the movies
, we get only
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that have the reÓ. (In other words,
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 41
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 42
HQWLW\EHDQUHODWLRQVKLSV
<PMXZWJTMU_Q\P][QVO+ WTTMK\QWV\aXM[
)MAGINE YOU WANT TO USE THE $IRECTOR3CHEMA TO RETURN ALL THE
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$IRECTOR HAS A #-2 lELD FOR MOVIES AND EACH MOVIE HAS A #-0
lELD FOR GENRE 3O WE COME UP WITH SOMETHING LIKE THIS
glance,
Þrst
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but WATCH
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 43
XVLQJFROOHFWLRQVLQDSDWK
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9OU CANT USE THE DOT NAVIGATION WHEN SOMETHING YOURE USING
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ABOVE IS ALMOST EXACTLY LIKE THIS 7(%2% CLAUSE WE HAD BEFORE
:+(5(GPRYLHVJHQUH µ+RUURU¶ 6 W
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WITH ACCESSORS YOU CAN THINK OF IT JUST LIKE THIS
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 44
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4HE ). OPERATOR FOR THE &2/- CLAUSE LETS YOU REFER TO A
#OLLECTION BUT NAME AN IDENTIlER AS REPRESENTING /.%
MEMBER OF THE #OLLECTION
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:+(5(PJHQUH µ+RUURU¶
Now ÒmÓ represents an individual
Movie IN the movies Collection
(a CMR Þeld of Director)
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and looks through ea all of the Directors,
Director, and looks fochr of the Movies of each
that matches ÔHorror a Movie with a genre
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set (no duplicates becaÕ. use
we said ÒDISTINCTÓ
of Directors
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Page 45
Return to Table of Contents
(-%4/%(7:((1
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,ETS SAY YOU WANT TO lND MOVIES IN THE DATABASE MADE IN THE
S AND S BUT YOU WANT TO EXCLUDE ANY MOVIES MADE IN OR REALLY BAD MOVIE YEARS
9OU COULD SAY
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 47
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 48
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Page 49
Return to Table of Contents
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 50
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 51
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 52
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 61
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
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Chapter 7. When Beans Relate
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Page 62
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
Return to Table of Contents
Page 63
PRFNH[DPDQVZHUV
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'IVEN #-0 BEANS #USTOMER"EAN /RDER"EAN AND ,INE)TEMS"EAN WITH THE
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Page 64
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7HATS TRUE ABOUT %*" 1, PATH EXPRESSIONS #HOOSE ALL THAT APPLY
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 7. When Beans Relate
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Chapter 7. When Beans Relate
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 8. Getting the Message
Table of Contents
Chapter 8. Getting the Message................................................................... 1
Section 8.1. OBJECTIVES............................................................................................................................................................... 2
Section 8.2. Imagine this scenario.................................................................................................................................................. 3
Section 8.3. Too bad these guys aren't message-driven beans....................................................................................................... 5
Section 8.4. Message-driven bean class........................................................................................................................................ 10
Section 8.5. Writing a message-driven bean: your job as Bean Provider..................................................................................... 11
Section 8.6. Sharpen your pencil................................................................................................................................................... 11
Section 8.7. Notice something missing from the code?................................................................................................................ 13
Section 8.8. Complete DD for a message-driven bean................................................................................................................. 13
Section 8.9. Topics and Queues.................................................................................................................................................... 14
Section 8.10. There are no: Dumb Questions............................................................................................................................... 16
Section 8.11. Only ONE bean per pool gets a copy of a topic message......................................................................................... 17
Section 8.12. With a queue, only one bean gets the message. Period.......................................................................................... 18
Section 8.13. MessageDrivenContext............................................................................................................................................ 19
Section 8.14. MessageDrivenContext........................................................................................................................................... 20
Section 8.15. message acknowledgement..................................................................................................................................... 22
Section 8.16. That's all well and good, but let's go back and see how our earlier scenario ended.............................................. 23
Section 8.17. Off the path: Think about it..................................................................................................................................... 24
Section 8.18. COFFEE CRAM....................................................................................................................................................... 27
Section 8.19. COFFEE CRAM....................................................................................................................................................... 30
Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safari ID: doannn16@yahoo.com
Print Publication Date: 2003/10/01
User number: 896963 Copyright 2008, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that
otherwise violates the Safari Terms of Service is strictly prohibited.
Chapter 8. Getting the Message
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Page 12
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Chapter 8. Getting the Message
Head First EJB™ By Bert Bates, Kathy Sierra ISBN: 0596005717 Publisher: O'Reilly
Prepared for Linda Martin, Safar