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Understanding JSP Session Management and Architecture Models for Web Applications

This overview explains the two primary architectures used in JavaServer Pages (JSP) for dynamic web applications: Model 1 and Model 2. It highlights the differences between these architectures, with Model 1 being suitable for simple applications, while Model 2 follows the MVC pattern for more complex applications. Additionally, it delves into session management, defining sessions, explaining session tracking mechanisms, and outlining how cookies, URL rewriting, and hidden fields maintain user data across multiple requests. This knowledge is essential for developing interactive web applications.

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Understanding JSP Session Management and Architecture Models for Web Applications

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  1. Session Management

  2. Review • 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

  3. Objectives • Define session • Explain and implement session tracking mechanism • Describe session lifecycle • Extend Java Server Pages

  4. Introducing Session • A long-term connection using the session layer of a network protocol • The Web server identifies requests and responses across a network connection as a single working session • Session acts as a link between the Web server and the client events • Web server uses the session to post client events to the server objects

  5. Introducing Session - Contd… • JSP uses the sessions to store unique data of a particular client connected to a Web application Sessions for two Web browsers(Clients)

  6. Methods in Session

  7. Methods in Session - Contd…

  8. Overview of Session Tracking Mechanisms • 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

  9. Implementing Session Tracking – Mechanisms • Server-side technologies maintain the information on the Web server • The server creates a session Id for the user logged in to the Web site and sends the session Id to the user computer • The session tracking feature contained in the servlets or JSP container maintains the state of a Web browser

  10. Session Tracking - Contd… • Information is sent to the browser in three ways, which include: • Cookies • URL Rewriting • Hidden form field method

  11. Cookies • 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

  12. Cookies – Contd… • Cookies help to maintain a single session for a user browsing the Web site

  13. Cookies – Contd… • 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.

  14. URL Rewriting • 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

  15. URL Rewriting – Contd… The session ID is encoded in the URLs that are created by the JSP pages

  16. 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> URL of server side program Provides check box for different products Submits the user input to URL

  17. 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> 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

  18. URL Rewriting – Contd… • 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 .

  19. Hidden Form Fields Method • Information from the Web browser is returned to the Web server in the form of HTTP parameters • 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 • Helps to carry the information from one HTML page to another

  20. Hidden Form Fields – Contd… • When the user visits the next page, the server side program reads all the parameters that a user passes in the previous form

  21. Hidden Form Fields Example <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> Hidden input field Provides check box for user input Submits user input to the server side program

  22. Hidden Form Fields – Contd… • 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.

  23. Session Life Cycle • 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.

  24. Using Session Object • Session object can be used to store and read data. • The session object acts almost like a bulletin board from where the objects can be written or read

  25. Using Session Object - Contd… • The request() method requests for the session object. … … // Obtain a session object HttpSession session = request.getSession(true); //Add an item to the session Integer sessionData = new Integer (100); Session.putValue(“IntValue”, sessionData); … … Obtains a session object Adds item to the session object

  26. Using Session Object - Contd… • The session value can be read and cast to the appropriate object type. … // 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(); … … Obtains a session object Reads the session value Casts the session value to appropriate datatype

  27. Using Session Objects – Contd… • 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/> Accepts userid If sessionval is null, the value of sessionval is set to userid. Removes the session Invalidates the session

  28. Using Session Object – Contd… • 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.

  29. Extending Java Server Pages • 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

  30. Superclass • A superclass must implement the HttpJspPage interface to use the HTTP protocol or it must implement the JSP interface. • The superclass should include: • 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

  31. JSP Sub-class • 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 sub-classing conditions

  32. Summary • 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() • getAttributeNames() • getCreationTime() • getId() • getLastAccessedtime() • getMaxInactiveInterval() • removeAttribute() • setAttribute() • setMaxInactiveInterval()

  33. Summary – Contd… • 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

  34. Summary – Contd… • 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.

  35. Q & A

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