Java EE (Java Enterprise Edition) General Discussion

Hi All,
When i tried to forward page, i am getting an exception called java.lang.IllegalStateException: invalidate: Session already invalidated
please look into below code. Please advice me what i am doing wrong.
I am using tomcat server
java.lang.IllegalStateException: invalidate: Session already invalidated
at org.apache.catalina.session.StandardSession.invalidate(StandardSession.java:1027)
at org.apache.catalina.session.StandardSessionFacade.invalidate(StandardSessionFacade.java:211)
at org.apache.catalina.session.StandardSessionFacade.invalidate(StandardSessionFacade.java:211)
at org.apache.jsp.checkLogin$jsp._jspService(checkLogin$jsp.java:157)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:201)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:381)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:473)


<%@ page language="java" import="cart.*,java.util.*" %>
<jsp:useBean id="loginBean" scope="page" class="cart.Login">
</jsp:useBean>
<jsp:useBean id="monitor" scope="application" class="java.util.HashMap" />

<%

String display="showLogin.html";
User user=loginBean.authenticate();

if(user!=null)
{
user.setIPAddr(request.getRemoteHost());
if(monitor.containsKey(user))
{
HttpSession oldSession=(HttpSession)monitor.get(user);
oldSession.invalidate();
}
session.setAttribute("user",user);
monitor.put(user,session);
System.out.println("Assigned new session for :"+user);
session.setMaxInactiveInterval(900);
display="browse.jsp";
}
%>
<jsp:forware page="<%=display %>"/>