Lecture13
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CS441
CURRENT TOPICS IN
PROGRAMMING LANGUAGES
Lecture 13
George Koutsogiannakis/Summer 2011
1
Topics
• Performance comparison between RMI and
RMI over IIOP.
• Example of Applet and Servlet
Communications.
• Example of applet/servlet/RMI over IIOP
server communications.
• Java Beans in Standard Edition jdk.
• Using Net Beans
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RMI and RMI over IIOP
Performance
• In general RMI over IIOP is slower than RMI because of :
– The IDL conversions needed.
– The additional layers in the architecture of RMI over IIOP.
• It is, however, depended on the amount of data transferred
during each invocation, and the type of data being
transferred.
– IIOP packets can carry more data than RMI packets
(approximately 80% more).
– The set up for the packets is, however, greater for IIOP than it is
for RMI (because of the additional layers).
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RMI and RMI over IIOP
Performance
– There is a point where for large amounts of data transfers IIOP
can become more efficient than RMI but it also depends on the
number of invocations that need to be made.
– Because of the Distributed Garbage Collector RMI
invocations can take a longer time than RMI over IIOP
invocations.
– Therefore for large amounts of data to be transferred over a
small number of invocations ,RMI over IIOP may be more
effective.
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RMI and RMI over IIOP
Performance
Time
increases
RMI over IIOP
RMI
Size of data increases
This graph applies for a specific data type of data
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Example of Applet and Servlet
Communications
• The following example illustrates how an applet (client side execution)
can communicate with a servlet (server side execution).
– The example web application is called LoginAppletNORMI and it is posted on the
examples page of the course ‘s web site.
• Architecture:
Web Server
Web App: LoginAppletNORMI
LoginApplet.html
LoginApplet.jar
WEB-INF
web.xml
classes
TestLoginServlet .class
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Example of Applet and Servlet
Communications
• Develop web application outside Tomcat in some folder
with the name of the web application:
– i.e. folder name: LoginAppletNORMI
• jar the applet .class files and place them in the web
application folder.
• Make sure that you have the directory structure required
for a web application:
– i.e WEB-INF folder with the web.xml inside and another folder
name d: classes.
– Place the servlet class in the classes folder.
– You can also create a folder named lib and place a copy of the jar
file there.
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Example of Applet and Servlet
Communications
• Create a war file:
– Open a DOS window with the path inside the web application
folder. Type the command:
>C:\web application folder> jar LoginAppletNORMI.war .
– Notice that the name of the war file war file is the same as the
name of the web application folder.
• Go to: http://localhost:8080/manager and log in as an
administrator.
– At the bottom of the page browse to where the war file is located
and then press deploy.
– You web application is now deployed in Tomcat.
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Example of Applet and Servlet
Communications
• You can now test it by:
– Opening a Browser instance and typing:
http://localhost:8080/LoginAppletNORMI/Login
Applet.html.
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Example of Applet and Servlet
Communications
• LoginApplet.html file:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Untitled</title>
</head>
<body><p>I am calling Applet</p>
<applet code="LoginApplet.class" archive="LoginApplet.jar” Width="500"
Height="500"></applet>
</body>
</html>
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Example of Applet and Servlet
Communications
LoginApplet.java code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;
public class LoginApplet extends JApplet
{
Container c;
JTextField ltf=new JTextField();;
String login;
JButton exitbutton, submitbutton;
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Example of Applet and Servlet
Communications
public void init()
{
c=getContentPane();
ltf.setEditable(true);
BorderLayout bl=new BorderLayout();
setLayout(bl);
c.add(ltf, BorderLayout.NORTH);
exitbutton=new JButton("Exit");
MyPanel mp=new MyPanel();
c.add(exitbutton, BorderLayout.SOUTH);
c.add(mp, BorderLayout.CENTER);
Handler h=new Handler();
ltf.addActionListener(h);
submitbutton.addActionListener(h);
exitbutton.addActionListener(h);
}
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Example of Applet and Servlet
Communications
class MyPanel extends JPanel
{
public MyPanel()
{
submitbutton=new JButton("Submit");
add(submitbutton);
}
}
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Example of Applet and Servlet
Communications
class Handler implements ActionListener
{
public void actionPerformed(ActionEvent e){
if(e.getSource()==exitbutton){
System.exit(0);
}
else if(e.getSource()==submitbutton){
System.out.println("Inside handler for submit button");
try{
login=ltf.getText();
URL url=new URL("http://localhost:8080/LoginAppletNORMI
/TestLoginServlet?loginname="+login);
URLConnection uc=url.openConnection();
uc.setDoOutput(true);
uc.setDoInput(true);
ltf.setText("I sent info to servlet");
InputStreamReader instream=new InputStreamReader(uc.getInputStream());
BufferedReader in=new BufferedReader(instream);
ltf.setText("I am reading input stream now");
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Example of Applet and Servlet
Communications
String line;
while((line=in.readLine())!=null)
{
ltf.setText(line);
}
in.close();
System.out.println("I finished try block. Name="+" "+login);
}
catch(MalformedURLException exception){ltf.setText("Malformed exc."); }
catch(IOException exception){ltf.setText("IO exc."+exception.getMessage());}
System.out.println("I finished actionPerformed");
}
}
}
}
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Example of Applet and Servlet
Communications
TestLoginServlet.java code:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class TestLoginServlet extends HttpServlet
{
protected void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
String login=req.getParameter("loginname");
res.setContentType("text/html");
PrintWriter out=res.getWriter();
if(login.equals("george"))
out.println("The servlet verifies that your name is:"+login);
else
out.println("Wrong login name. Please try again");
out.close();
}
}
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Example: ServletLoginApplet
web application
• This example simulates the communications between an
applet and a servlet which acts as a client for an RMI over
IIOP server.
• The applet sends a request to the servlet.
• The servlet in turn is a client to an RMI server. It sends a
request to the RMI server. The RMI server returns a
response to the servlet which in turn sends a response to
the applet.
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Example: ServletLoginApplet
web application
• This application requires that:
– Deployment in Tomcat of the web application
part
• A signed jar file for the applet.
• A html file that calls the signed applet via the archive attribute
of the applet tag.
• A servlet under the WEB-INF/classes path.
• The class ReverseInterface.class under the WEB-INF/classes
path.
– This is the interface file from the RMI over IIOP server
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Example: ServletLoginApplet
web application
• The stub file from the RMI over IIOP server called:
_ReverseInterface_stub.class under the path
WEB-INF/classes
• A web.xml file under the WEB-INF folder.
– Deploy using a war file as in previous example.
– The RMI over IIOP server classes (interface,
implementation class tie class etc.) should
reside in a path outside of Tomcat.
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Example: ServletLoginApplet
web application
• To test the web application certain tasks have to be done in
the proper sequence:
– From the folder where the RMI over IIOP server is located start an
instance of the naming service (registry):
C:\........>tnameserv –ORBInitialPort
– Next start the RMI over IIOP server:
C:\>……>java Djava.naming.factory.initial=com.sun.jndi.cosnaming.CNCtxFactory
-Djava.naming.provider.url=iiop://localhost:900 ReverseInterfaceImpl
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Example: ServletLoginApplet
web application
– Next, start an instance of the Browser and type:
http://localhost:8080/ServletRMIIIOP/IIOPLoginApplet.html
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Example: ServletLoginApplet web
application
Applet streams (POST HTTP request)
URL url=new URL("http://localhost:8080/ServletRMIIIOP/IIOPTestLoginServlet");
qr="qr="+URLEncoder.encode(query);
textarea.append("\n"+"The applet displays"+qr+"\n");
URLConnection uc=url.openConnection();
uc.setDoOutput(true);
uc.setDoInput(true);
uc.setUseCaches(false);
ByteArrayOutputStream bytestream=new ByteArrayOutputStream(512);
PrintWriter out=new PrintWriter(bytestream,true);
out.print(qr);
out.flush();
//POST requests are required to have Content Length
String lengthString=String.valueOf(bytestream.size());
uc.setRequestProperty("Content-Length", lengthString);
uc.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
bytestream.writeTo(uc.getOutputStream());
out.flush();
out.close();
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Example ServletLoginApplet
web application
InputStreamReader in=new InputStreamReader(uc.getInputStream());
int chr=in.read();
while(chr!=-1)
{
textarea.append(String.valueOf((char)chr));
chr=in.read();
}
in.close();
System.out.println("I finished try. Name="+" "+query);
}
catch(MalformedURLException exception){textarea.setText(e.toString()); }
catch(IOException exception){textarea.setText(e.toString());}
System.out.println("I finished actionPerformed");
}
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Example: ServletLoginApplet
web application
Servelt code:
import javax.naming.*;
import java.util.*;
public class IIOPTestLoginServlet extends HttpServlet
{
protected void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
String qr=req.getParameter("qr");
String loginmod="The name is:"+" "+qr+" "+"Therefore the servlet works with doPost";
res.setContentType("text/html");
PrintWriter out=res.getWriter();
out.println(loginmod);
out.println("The servlet captured the value of qr="+qr);
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Example: ServletLoginApplet
web application
ReverseInterface r;
Hashtable env=new Hashtable();
env.put("java.naming.factory.initial", "com.sun.jndi.cosnaming.CNCtxFactory");
env.put("java.naming.provider.url", "iiop://localhost:900");
try{
out.println("TRYING TO CONTACT REGISTRY");
Context initialNamingContext=new InitialContext(env);
out.println("obtained InitialContext");
r=(ReverseInterface)PortableRemoteObject.narrow(
initialNamingContext.lookup("Reverse"), ReverseInterface.class);
out.println("The registry lookup was successful");
out.println("the opposite of "+qr+"is"+r.reverseString(qr));
}
catch (Exception e) {
out.println("Error executing remote method or lookup 1:30 p.m.");
out.println(e.toString());}
out.close();
}
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Example ServletLoginApplet
web application
RMI over IIOP server
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface ReverseInterface extends Remote
{
String reverseString(String originalstring) throws RemoteException;
}
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Example ServletLoginApplet
web application
import java.rmi.*;
import java.rmi.server.*;
//add the lines below
import javax.rmi.PortableRemoteObject;
import javax.naming.*;
import java.net.*;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class ReverseInterfaceImpl extends PortableRemoteObject implements ReverseInterface
{
public ReverseInterfaceImpl() throws RemoteException
{
super();
}
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Example ServletLoginApplet
web application
public String reverseString(String originalstring) throws RemoteException
{
int length=originalstring.length();
StringBuffer temp=new StringBuffer(length);
for (int i=length; i>0; i-- )
{
temp.append(originalstring.substring(i-1,i));
}
return temp.toString();
}
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Example ServletLoginApplet
web application
public static void main(String[] args){
try{
ReverseInterfaceImpl r= new ReverseInterfaceImpl();
Context initialNamingContext=new InitialContext();
System.out.println("Binding server to registry..");
initialNamingContext.rebind("Reverse",r);
System.out.println("Object was registered");
}
catch(Exception e) {
System.out.println("Error while binding object 11:00am");
System.out.println(e.toString());
}
System.out.println("The RMI server is up and Running!");
}
}
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Example ServletLoginApplet
web application
Command to start RMI over IIOP server:
C:\.....>java -Djava.naming.factory.initial=com.sun.jndi.cosnaming.CNCtxFactory
-Djava.naming.provider.url=iiop://localhost:900 ReverseInterfaceImpl
Command to compile server with rmic compiler:
C:\......>rmic -iiop ReverseInterfaceImpl
Notice that the rmic command should be done
after the server file has been compiled with the
normal javac compiler.
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Java Beans
• The Java Beans architecture is based on the component model.
– Components are self sustained reusable software modules.
• The idea behind Java Beans is that we can introduce customization of
the component during run time (dynamically).
• Java Beans Architecture promotes reusability but it is different than
inheritance. Inheritance is introduced at compilation time. Any
changes result to recompilation.
– Java Beans, however, have their properties changed by another class dynamically
during run time.
– A java Bean can be used by another Java Bean thus resulting in a new Java Bean
which is the combination of the two.
• Java Beans expose their properties to other Beans.
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Java Beans
• Internal workings of the Java Bean are hidden from the
user.
• All the user needs to know is what functionality the Bean
offers and what interface it provides.
– The user can access and set properties of the Bean as needed
during run time.
• In Java Standard Edition Beans are supported via the
packages:
– java.beans
– java.beans.beancontext
• Other languages have similar concept to Beans such as Delphi and
Visual Basic.
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Java Beans
Bean
A
Bean B
Bean C
Bean C combines the functionality of Bean A and Bean B
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Java Beans
• To write a Java Bean we need:
– Rules that ensure consistency in writing interfaces: i.e
accessor method names begin with get, mutator
methods begin with set.
• Bean properties must use get /set followed by the property’s
name i.e. String LastName; public String getLastName();
• Properties of a Bean can be:
–
–
–
–
–
Simple: String LastName ( contains a single value) .
Indexed: to keep track of the values of a group of properties.
Bound: alert other objects when its value changes.
Constrained: notifies other objects of impending changes
Read/Write, read-only, write-only
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Java Beans
– An event handling model.
– Persistence. Retaining information about the state of an object.
– Introspection: Discover how to access other Java Bean
components.
– We need support from a Builder IDE. The IDE will allow
connection of Java Beans to produce the final application. Such an
IDE can be NetBeans.
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Java Beans
• Introspector class
– java.beans.Introspector provides a standard way for
building tools to learn about the properties, events and
methods supported by a target java bean.
– The introspector will analyze the bean’s class and
superclass looking for its accessor and mutator
methods, event methods and so on.
– Introspection will also look for explicit information that
can be provided about a Bean via a BeanInfo class
provided by the developer of the Bean.
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Java Beans
37
Java Beans
• For example, the builder tool in the previous slide shows a calculator
component that is built from:
– 16 button components,
– a text field component,
– and a panel upon which the buttons and a text display are placed.
– In addition, you can see five invisible components. These specific
components hold values or strings used by the calculator for
intermediate calculations, operation codes, and display strings, as
well a boolean flag to determine when evaluation of a new
expression is started.
• The calculator shown becomes itself a component that can
be integrated in another application
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Java Beans
• More information about Java Beans is
provided in the Java Beans Specification
available at:
http://java.sun.com/javase/technologies/desktop/javabeans/docs/spec.
html
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Java Beans
• To create a simple Bean and import it in a
tool like Net Beans :
– Create the Java Bean program. Notice that all
Java Bean classes must be serializable.
– Create a Manifest File
– Jar the files
– Import into the tool
Note: A Java Bean can also be created outside the builder
tool by having the developer write the code for it.
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Creating A Java Bean
programmatically
• Java Beans are normally stored and distributed in jar files.
– The jar file must contain a manifest file which describes the contents of the jar file.
• Contents are defined under specific headers in the manifest file.
• The manifest file is read by the IDE (Builder) tool when we load the Bean on
the IDE.
• To create the manifest file we can use a text editor i.e
Main-Class: folder1.folder2.MyBean
Name: folder1.folder2.MyBean.class
Java-Bean: True
• The file needs to be saved as manifest.tmp.
>jar cmf manifest.tmp MyBean.jar MyBean.class
• The jar utility uses the file manifest.tmp to create the file MANIFEST.MF and
place it in a directory called META-INF inside the jar.
Note: The jar file can also become an executable. In other words we can execute
the program just by double clicking on the icon of the jar file (at least in
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Windows platforms).
Creating A Java Bean
programmatically
• To confirm the file is in the jar use the command:
>jar tvf MyBean.jar
• The jar file can also be executed via the command:
> java –jar MyBean.jar
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Development Environments
• There are Development Environments for learning
purposes.
– A tool like that was the BDK-Bean Development Kit
(not available any more) offered by SUN
– Another tool like that offered is the BeanBuilder
available at:
https://bean-builder.dev.java.net/
• Neither of these tools is suitable for a production
environment
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Net Beans IDE
• An IDE that allows the creation of GUIs via
drop and drag actions.
• The creation of Enterprise Java Beans.
• A small example of how the Net Beans IDE
can be used to create a GUI is described in
file: netbeansGUI.doc posted in the
examples page of the course’ s web site.
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Net Beans IDE
• Install NetBeans 6.5 or higher from the
netbeans.org site. Use the choice that
includes all.
• Before installation make sure:
– That you have installed Java SDK with EE.
45
Net Beans IDE
• During installation of NetBeans:
– Make sure that you choose the customization
choice:
• Add Tomcat as part of the installation
– Make sure that you choose the SDK/jdk path as
the jdk to be used by NetBeans.
• Check PATH variable to make sure that is shown as
SDK/bin
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Net Beans IDE
• Make sure that you record all port numbers and
passwords.
– The Tomcat passwords need to be recorded. If
for some reason you forget you can recover the
Tomcat passwords from file:
C:\Users\YourUserNamefor your
system\.netBeans\6.5\apatche-tomcat6.0.18_base\conf\tomcat-users.xml
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Net Beans IDE
• After NetBeans installation is completed:
– Go to services and right click to add the
GlassFish 2 server as a server (or GlassFish 3).
– You will be asked to create a Domain for your
applications. Choose “Create Personal
Domain”.
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Net Beans IDE
• Create a Folder C:\GlassFishDomains in windows
explorer first.
• In the NetBeans window type:
C:\GlassFishDomains\Domains
• The system will create the folder Domains and place
the required files in it.
• You will be asked to create a password to access the
administrative console of GlassFish.
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Net Beans IDE
• Make a note of the system paths to the
various installations.
• Make a note of port numbers
– i.e due to conflicts with exiting usages of port
numbers Tomcat make work in port 8084 now.
• If you deploy a web application using
GlassFish, then you do not need to deploy it
in Tomcat also.
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Net Beans IDE
• Notice that under services Tomcat and
GlassFish appear as separate services.
– i.e. You can deploy a web service that does not
have beans in it in Tomcat and not bother with
GlassFish.
– You will deploy on Tomcat using the manager
page of Tomcat and a war file.
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Study Guide
• Study slides.
• Suggest that you experiment with Bean
Builder tool.
• Download and start experimenting with Net
Beans
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