Java EE (Java Enterprise Edition) General Discussion

hi, I want to display a message on jsp page when session expires.I did the following

set <session-config> in web.xml

<session-config>
      <session-timeout>2</session-timeout>    <!-- 2 minutes -->
    </session-config>

Then I check each jsp page with following code.

if(session.isNew()){
	response.sendRedirect("display.jsp?reqSes=new");
} 

Now everything works correctly.When I modify the display.jsp page as below it is giving 500 error which is a null pointer exception.

if(request.getParamter("reqSes") != null){
out.println("Session Expired");}

this error occurs only when page is redirected from another jsp page, if the page is called first time it doesn't happen.
What is it I need to modify to work correctly.