Getting NullPointerException while counting number of visitors using session

[Punit Jain]

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class VisitorsUsingSession extends HttpServlet {
	private static final long serialVersionUID = 1L;
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
		HttpSession session = request.getSession(false);
		if(session == null)
		{
			request.getSession(true);
			Integer hitCount = new Integer(0);
			session.setAttribute("count", hitCount);
		}
		Integer hitCount = (Integer) session.getAttribute("count");
		hitCount = new Integer(hitCount.intValue()+1);
		session.setAttribute("count",hitCount);
		response.getWriter().print("Number of times user visits is"+hitCount.intValue());
	}
}

i am getting a NullPointerException in this code??

[Bear Bibeault]

Where?

[Punit Jain]

At line 16..

here is the exception



HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
VisitorsUsingSession.doGet(VisitorsUsingSession.java:16)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.

[Prasad Krishnegowda]

Punit Jain wrote:

		if(session == null)
		{
			request.getSession(true);
			Integer hitCount = new Integer(0);
			session.setAttribute("count", hitCount);
		}	

It obviously throws NullPointerException, because you check if session is null, if its null, then you call session.setAttribute, perhaps you forgot to assign session in above line, i.e request.getSession(true), it should have been session = request.getSession(true)

[Punit Jain]

okay, working now....thanks...
one more thing i want to know, when my session gets expired...
what i was expecting is, when i close my browser my session gets expired, apart from browser even when i m stopping my server my session is not expiring...

please let me know where i m going wrong??

[Bear Bibeault]

The server has no idea that you have closed the browser. How can it expire the session when that happens? The session will eventually time-out.

[Punit Jain]

Bear Bibeault wrote:The server has no idea that you have closed the browser. How can it expire the session when that happens? The session will eventually time-out.

okay so either it will eventually time out, otherwise i have to set session Timeout..?

[Bear Bibeault]

If you don't set a timeout value it will use the default (whatever your container uses).

[Punit Jain]

Bear Bibeault wrote:If you don't set a timeout value it will use the default (whatever your container uses).

okay, can i see what my container/tomcat, default timeout value??

[Bear Bibeault]

Well, Tomcat uses the conf/web.xml config file as the default for all web apps. Maybe you should look in there.

[Punit Jain]

okay, i got it, it's 30....
Thank you.....

[Bear Bibeault]