© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Review
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Page-centric designs in JSP are called Model 1 architecture
Model 1 architecture is used for simple applications and generates dynamic content
Model 2 architecture is suitable for large and complex applications as it uses a combination of servlets and JSP
Model 2 applications are based on Model-View-Controller (MVC) pattern
MVC pattern contains a Model, View, and Controller
RequestDispatcher interface forwards the request from a JSP page or a servlet to other resources, such as HTML file, servlet, or a JSP page
The two methods in RequesDispatcher interface are include() and forward()
Errors in JSP page include Translation time and Request time errors
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Objectives
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Define session
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Explain and implement session tracking mechanism
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Describe session lifecycle
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Extend Java Server Pages
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Introducing Session
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A long-term connection using the session layer of a network protocol
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The Web server identifies requests and responses across a network connection as a single working session
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Session acts as a link between the Web server and the client events
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Web server uses the session to post client events to the server objects
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Introducing Session Contd…
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JSP uses the sessions to store unique data of a particular client connected to a Web application
Sessions for two Web browsers (Clients)
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Methods getAttribute() getAttributeNames() getCreationTime()
Description
Returns the object with specified name defined in the session. The getAttribute() method returns null if object is not found
Returns list of objects defined in the session
Returns the creation time of the session in milliseconds since midnight January 1, 1970 GMT getId() Returns the unique identifier which is the session
Id, as a string getLastAccessedTime() Returns the time of last client request with the session. The time is returned as number of milliseconds since midnight January 1, 1970 GMT
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Methods Description getMaxInactive
Interval()
Returns the maximum time interval of the session. The servlet container keeps the session open till the user accesses the Web site removeAttribut e()
Removes the object associated with the specified string from the session setAttribute() Associates an object with the specified key string and stores it to the session setMaxInactive
Interval()
Specifies the time interval in seconds between the client requests before the servlet container will invalidate this session
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Maintains a session till the user is browsing the Web site
Used in interactive Web applications to store the information of the user logged in to the Web site
The information stored is used to identify the user sending a request to the Web server
Session tracking helps to maintain the session information and keeps track of the multiple requests made by the client
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

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Server-side technologies maintain the information on the Web server
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The server creates a session Id for the user logged in to the Web site and sends the session Id to the user computer
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The session tracking feature contained in the servlets or JSP container maintains the state of a
Web browser
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Session Tracking Contd…
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Information is sent to the browser in three ways, which include:
 Cookies
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URL Rewriting
Hidden form field method
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Cookies
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Cookies are text files stored on the user’s computer containing the session Id of the user sent by the
Web server
The cookie is sent back to the Web server with every subsequent request made by the user in the same session
The cookie includes a name, a single value and optional attributes
Cookies are used for maintaining sessions and do not have an expiration time
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Cookies – Contd…
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Cookies help to maintain a single session for a user browsing the Web site
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Cookies – Contd…
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Advantages of Cookies are:
 Remember user IDs and password.
 To track visitors on a Web site for better service and new features.
 Cookies enable efficient ad processing.
Disadvantages of Cookies are:
 The size and number of cookies stored are limited.
 Personal information is exposed to the other users.
 Cookies fails to work if the security level is set too high in the Internet browser.
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

URL Rewriting
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JSP hides the details of a cookie-based session tracking and supports the URL rewriting mechanism
URL Rewriting works with Web browsers that do not support cookies or the cookies that are disabled on a Web browser
Each URL that references the Web browser is returned to the user and contains additional information
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The session ID is encoded in the URLs that are created by the JSP pages
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URL Rewriting – Contd…
<b>Search results for books</b>
<form method="post" action="serverprogram.jsp">
<input type="checkbox" name="productID" value="100">CD MP3 Converter Kit For Your
CAR<br>
<input type="checkbox" name="productID" value="101">Front Loading Car MP3/CD Player With
Anti Shock Memory and FM<br>
<input type="checkbox" name="productID" value="102">CAR/Home DVD/VCD/MP3 Playerwith anti shock for Indian Roads<br>
<input type="submit" name="Submit" value="Add to
Cart"><br>
</form>
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URL of server side program
Provides check box for different products
Submits the user input to URL
04e-BM/NS/HDCV/FSOFT v2/3

URL Rewriting Contd…
<b>Search results for books</b>
<form method="post" action="serverprogram.jsp?productID=102">
<input type="checkbox" name="productID" value="150">DVD Player with built in Amplifier
<br>
<input type="checkbox" name="productID" value="160">Ultra Slim DVD Player Multi
Region 5.1 Digital<br>
<input type="submit" name="Submit" value =
"Add to Cart">
<br>
</form>
© FPT SOFTWARE – TRAINING MATERIAL – Internal use
URL for server side program after the user selects a product and goes to another page
Provides check box for different products
Submits input to the URL
04e-BM/NS/HDCV/FSOFT v2/3

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Disadvantages of Cookies are:
 Server side processing is tedious.
 Every URL that is returned to the user should have additional information appended to it.
 If the user leaves the session and opens the
Web page using a link or bookmark then the session information is lost .
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Hidden Form Fields Method
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Information from the Web browser is returned to the Web server in the form of HTTP parameters
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Utilizes the hidden fields in an HTML page
Hidden fields in the form are used to send the information to the Web browser
Stores information about a session
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Helps to carry the information from one HTML page to another
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

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When the user visits the next page, the server side program reads all the parameters that a user passes in the previous form
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Hidden input field
Provides check box for user input
Submits user input to the server side program
<b>Search results for books</b>
<form method="post" action="serverprogram.jsp">
<input type="hidden" name="productID" value="100">
<input type="checkbox" name="productID" value="150">DVD
Player with Built in Amplifier <br>
<input type="checkbox" name="productID" value="160">Ultra
Slim DVD Player Multi Region 5.1 Digital<br>
<input type="submit" name="Submit" value="Add to
Cart"><br>
</form>
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Hidden Form Fields – Contd…
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The advantages of hidden form fields are:
 Simplest way to implement session tracking
 Displays nothing on the HTML page but can be used to hold any kind of data
 Helps to maintain a connection between two pages
The disadvantage of hidden form fields is that this method of session tracking displays sensitive information to the user.
The information includes the data passed around to maintain a session.
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Session Life Cycle
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The server assigns a unique ID to the session created for a particular user request.
This session ID is passed to the client as a cookie or a hidden variable.
The session is considered new until the client returns the session ID to the server through a cookie or as a part of the requested URL.
A session exists on the server until it becomes invalid or the server is stopped.
The HttpSession objects are used to store the session data in the current servlet context.
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Using Session Object
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Session object can be used to store and read data.
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The session object acts almost like a bulletin board from where the objects can be written or read
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

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The request() method requests for the session object.
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// Obtain a session object
HttpSession session = request.getSession(true);
//Add an item to the session
Integer sessionData = new Integer (100);
Session.putValue(“IntValue”, sessionData);
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Obtains a session object
Adds item to the session object
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

 The session value can be read and cast to the appropriate object type.
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// Obtain a session object
HttpSession session = request.getSession(true);
// Read the session data and cast it to the appropriate object type
Integer sessionInt = (Integer) session.getValue(“session”); int count = sessionInt.intValue();
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Obtains a session object
Reads the session value to appropriate datatype
04e-BM/NS/HDCV/FSOFT v2/3

 The session can be invalidated using the invalidate() method of the
HttpSession object.
<%
String sessionval=(String)session.getAttribute("userid"));
{ if(sessionval == null)
{ session.setAttribute("userid",sessionval); out.println(session.getAttribute("userid"));
} else out.println("User Session already created");
}
%>
<b>click this link to
<a href="<%=session.removeAttribute("userid")%>">remove session attribute</a></b><br/>
<b>click this link to <a href="<%=session.invalidate()%>"> invalidate the session</a></b><br/>
© FPT SOFTWARE – TRAINING MATERIAL – Internal use
Accepts
If to userid userid sessionval null, the value of sessionval is set
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Removes the session
Invalidates the session is
04e-BM/NS/HDCV/FSOFT v2/3

Using Session Object – Contd…
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The binding of objects to a request object is similar to the storing of the object in a session
An object bound to a request is available only for the life of that particular request
An object can be bound using the setAttribute(String key, Object obj) method in the HttpRequest interface
An object can be retrieved using the getAttribute(String key) method.
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Extending Java Server Pages
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The superclass may offer several benefits, such as, a set of utilities, which may not be offered by the standard packages
In order to extend a JSP from a superclass, both the superclass and the extended JSP must follow several requirements
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Superclass
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A superclass must implement the HttpJspPage interface to use the HTTP protocol or it must implement the JSP interface.
The superclass should include:
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All methods from the Servlet Interface and must be declared as final.
The Service() method that should invoke the
_ jspService() method.
The init() method that should invoke the jspInit() method.
The destroy() method that should invoke the jspDestroy() method
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

JSP Sub-class
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A JSP sub-class should provide jspInit() method and jspDestroy() method.
<%@ page extends = “servlet.JSPBase” %>
<%! public void jspInit(){ } public void jspDestroy(){ }
%>
<% out.println(“<B> User Name: </B>” + getUser(request) + “<P>”); out.println(“<B> Catalog: </B>” + getCatalog(request));
%>
Empty methods that satisfy the JSP subclassing conditions
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Summary
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Session is a long-term connection that uses the session layer of a network layer protocol
Session acts as a link between the server and the client events
Web server uses the session to post client events to the server objects
Server objects utilize the session for passing messages to the client and listening to client events
The different methods of session object includes:
 getAttribute()
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 getAttributeNames() getCreationTime() getId() getLastAccessedtime() getMaxInactiveInterval() removeAttribute() setAttribute() setMaxInactiveInterval()
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Summary – Contd…
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Session tracking maintains a session till the user browses the Web site
The session tracking feature contained in the servlets or JSP container maintains the state of a Web browser
Cookies are text files stored on the user’s computer containing the session Id of the user, sent by the Web server
A Cookie is sent back to the Web server with every subsequent request made by the user in the same session
URL rewriting works with Web browsers that do not support cookies or the cookies that are disabled on a Web browser
The information from the Web browser is returned to the server in the form of HTTP parameters
Hidden form fields are used to store information about a session.
Hidden form field helps to carry the information from one HTML page to another HTML page
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Summary – Contd…
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The server assigns a unique ID to the session created for a particular user request.
The HttpSession object is defined by the HttpSession interface, and is obtained using the getSession() method of the HttpServletRequest object.
Session object can be used to store and read data and acts almost like a bulletin board from where the objects can be written or read.
When the reading or writing operation is complete, the session can be invalidated using the invalidate() method of the HttpSession object.
Binding of objects to a request object is similar to the storing of the object in a session.
An object can be bound using the setAttribute(String key, Object obj) method in the HttpRequest interface, and can be retrieved using the getAttribute(String key) method.
A superclass must implement the HttpJspPage interface to use the HTTP protocol or it must implement the JSP interface.
A JSP sub-class should provide jspInit() method and jspDestroy() method.
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Q & A
© FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3