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Tutorials : Server-Side Web Applications Using Servlets and JSP :
: Session Tracking

Contents
What is Session Tracking?
The Session Tracking API
Example: Showing Session Information

Example: Showing Session Information

Here is a simple example that generates a Web page showing some information about the current session. You can also download the source or try it on-line. 

package hall;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.net.*;
import java.util.*;

/** Simple example of session tracking. See the shopping
 *  cart example for a more detailed one.
 *  <P>
 *  Part of tutorial on servlets and JSP that appears at
 *  http://www.apl.jhu.edu/~hall/java/Servlet-Tutorial/
 *  1999 Marty Hall; may be freely used or adapted.
 */

public class ShowSession extends HttpServlet {
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
      throws ServletException, IOException {
    HttpSession session = request.getSession(true);
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    String title = "Searching the Web";
    String heading;
    Integer accessCount = new Integer(0);;
    if (session.isNew()) {
      heading = "Welcome, Newcomer";
    } else {
      heading = "Welcome Back";
      Integer oldAccessCount =
        // Use getAttribute, not getValue, in version
        // 2.2 of servlet API.
        (Integer)session.getValue("accessCount");
      if (oldAccessCount != null) {
        accessCount =
          new Integer(oldAccessCount.intValue() + 1);
      }
    }
    // Use putAttribute in version 2.2 of servlet API.
    session.putValue("accessCount", accessCount);

    out.println(ServletUtilities.headWithTitle(title) +
                "<BODY BGCOLOR=\"#FDF5E6\">\n" +
                "<H1 ALIGN=\"CENTER\">" + heading + "</H1>\n" +
                "<H2>Information on Your Session:</H2>\n" +
                "<TABLE BORDER=1 ALIGN=CENTER>\n" +
                "<TR BGCOLOR=\"#FFAD00\">\n" +
                "  <TH>Info Type<TH>Value\n" +
                "<TR>\n" +
                "  <TD>ID\n" +
                "  <TD>" + session.getId() + "\n" +
                "<TR>\n" +
                "  <TD>Creation Time\n" +
                "  <TD>" + new Date(session.getCreationTime()) + "\n" +
                "<TR>\n" +
                "  <TD>Time of Last Access\n" +
                "  <TD>" + new Date(session.getLastAccessedTime()) + "\n" +
                "<TR>\n" +
                "  <TD>Number of Previous Accesses\n" +
                "  <TD>" + accessCount + "\n" +
                "</TABLE>\n" +
                "</BODY></HTML>");

  }

  public void doPost(HttpServletRequest request,
                     HttpServletResponse response)
      throws ServletException, IOException {
    doGet(request, response);
  }
}

Here's a typical result, shown after visiting the page several without quitting the browser in between:

This tutorial is now available as a book: Core Servlets and JavaServer Pages by Marty Hall, published by Sun Microsystems Press. Read all about it at CoreServlets.com
Server-Side Web Applications using Java Servlets versions 2.1/2.2 and JavaServer Pages (JSP) version 1.0: A Tutorial
© 1999-2000 Marty Hall.
All source code freely available for unrestricted use.
Created for work in the Research and Technology Development Center of the Johns Hopkins University Applied Physics Lab, for courses in the Johns Hopkins Part-Time MS Program in Computer Science, and for various industry seminars and on-site Java short courses.
Please note that this is a first draft of the tutorial, so please send corrections, comments, and suggestions to me at hall@apl.jhu.edu.
Reprinted with permission from the author. Click here to visit the original version

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