NullPointerException from HttpSessionFacade.invalidate()

Thu, 11 Jan 2001 10:16:38 -0800

Hi,

I am trying to build a login servlet and get a NullPointerException from HttpSessionFacade class in Tomcat 3.2.1.
The code of the simple version of the servlet which reproduces the
problem is attached at the end of this mail along with the stack trace of the Exception thrown.
This piece of code works fine on tomcat 3.1.1 but fails on tomcat 3.2.1
To reproduce the error,
1. start tomcat 3.2.1 afresh.
2. Login from a browser.The password field is not required as for now.
3. Open another browser (not a new instance of the same browser) on the same
machine or another machine.
4. Login with the same username.

the servlet does the following
1.it invalidates any existing session on this request.
2.it checks the context to find if the present user has any associated
session and if it is there tries to invalidate it. (This is where I get the
exception, given below).
3. creates a new session.
4. puts the new session into the context with the user id.

In tomcat 3.2 is the session object which I get ( actually HttpSessionFacade) valid only for the request or can span multiple Requests?
Any help would be greatly appreciated.
 
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Regds,
Gokul

========= 8<==== SERVLET CODE ========= 8< =======

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

public class TestSessionBehaviour
extends HttpServlet
{
 private static String STR="LOGIN.SESSION.USER.";
 public void doGet(HttpServletRequest req, HttpServletResponse res)
 throws IOException, ServletException
 {
  res.setContentType("text/html");
  PrintWriter out = res.getWriter();
  sendLoginPage(out);
  out.close();
 }

 public void doPost(HttpServletRequest req, HttpServletResponse res)
 throws IOException
 {
  String name = req.getParameter("id");
  HttpSession objSession = req.getSession(false);
  // if the present request has a session invalidate it.
  if(objSession != null)
   objSession.invalidate();
  // if this user has a valid session, invalidate it.
  objSession = (HttpSession)getServletContext().getAttribute(STR+name);
  if (objSession != null)
  {
   System.out.println("The session from context retrieved");
   try
   {
    objSession.invalidate();
   }catch(IllegalStateException ex)
   {   }
  }
  // create new session
  objSession = req.getSession(true);
  // store in the context the username and session.
  getServletContext().setAttribute(STR+name,objSession);

  // send reciept html
  res.setContentType("text/html");
  PrintWriter out = res.getWriter();
  sendReceipt(out);
  out.close();
 }


 private void sendReceipt(PrintWriter out)
 {
  out.println("<html><title>Receipt</title><body>The login is
recorded</body></html>");
 }


 private void sendLoginPage(PrintWriter out)
 {
  out.println("<html><title>Test Login</title><body>Please login <br><form
method=post> <table><tr>");
  out.println("<td>Name </td><td><input type=text name=id> </td></tr>");
  out.println("<tr><td>Password</td><td><input type=text
name=pass></td></tr>");
  out.println("<tr><td><input type=reset value=reset></td><td><input
type=submit value=login></td></table>");
  out.println("</form></body></html>");
 }

}

========= 8<===== EXCEPTION THROWN==== 8< =====

Internal Servlet Error:
java.lang.NullPointerException
 at
org.apache.tomcat.facade.HttpSessionFacade.invalidate(HttpSessionFacade.java
:136)
 at TestSessionBehaviour.doPost(TestSessionBehaviour.java:33)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
 at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
 at org.apache.tomcat.core.Handler.service(Handler.java:286)
 at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
 at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:79
7)
 at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
 at
org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpC
onnectionHandler.java:210)
 at
org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
 at
org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
 at java.lang.Thread.run(Thread.java:484)
========= 8<============= 8< =============
 
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