Session Tracking API

Every user is associated with a javax.servlet.http.HttpSession object were you can story any info about him.

You get it with

public HttpSession HttpServletRequest.getSession();

if now session then one is created.

You can add data to it with

public void HttpSession.setAttribute(String name, Object value);

and get its value with

public Object HttpSession.getAttribute(String name);

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

public class SessionTracker extends HttpServlet {

  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();

    // Get the current session object, create one if necessary
    HttpSession session = req.getSession();

    // Increment the hit count for this page. The value is saved
    // in this client's session under the name "tracker.count".
    Integer count = (Integer)session.getAttribute("tracker.count");
    if (count == null)
      count = new Integer(1);
    else
      count = new Integer(count.intValue() + 1);
    session.setAttribute("tracker.count", count);

    out.println("<html><head><title>SessionTracker</title></head>");
    out.println("<body><h1>Session Tracking Demo</h1>");

    // Display the hit count for this page
    out.println("You've visited this page " + count +
      ((count.intValue() == 1) ? " time." : " times."));

    out.println("<p/>");

    out.println("<h2>Here is your session data:</h2>");
    Enumeration e = session.getAttributeNames();
    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      out.println(name + ": " + session.getAttribute(name) + "<br/>");
    }
    out.println("</body></html>");
  }
}