JSP Session Timeout in multiple pages (iframes used)

Question

Hi,
Here is my scenario. I have a JSP Page i.e. A.jsp in which I am setting a session timeout to 3 minutes. I also have another JSP included i.e. B.jsp in the same page (A.jsp) using the following code i.e.
<IFRAME SRC="B.jsp" width="100%" height="800" frameborder="0" align="center">
         <!-- Alternate content for non-supporting browsers -->
</IFRAME>I am also setting a session timeout to 1 minute in the B.jsp. Now if the session timeout in one of the pages i.e. A.jsp or B.jsp I want to route to a different page i.e. C.jsp.
Now my problem is if the session timeouts in the B.jsp the C.jsp is shown inplace of the B.jsp page inside A.jsp. Means A.jsp still shows it's content at top and under it C.jsp is shown. I want to route to C.JSP page if a session timeouts in A.jsp or B.jsp and only show C.jsp.
Any help is appreciated.
Thanks

Answer 1

Where exactly I put the javascript. Here is currently I am checking for the session timeout:
String error = (String) request.getAttribute("Error");
    if (error != null)
        out.write("<center><strong>");
        out.write("<font color=\"Red\">");
        out.write(error);
        out.write("</font>");
        out.write("</strong></center>");
    response.setHeader("Cache-Control","no-cache"); //forces caches to obtain a new copy of the page from the origin server
    response.setHeader("Cache-Control","no-store"); //directs caches not to store the page under any circumstance
    response.setDateHeader("Expires", 0); //causes the proxy cache to see the page as "stale"
    response.setHeader("Pragma","no-cache"); //HTTP 1.0 backward compatibility
    String userName = (String) session.getAttribute("User");
    if (null == userName)
        request.setAttribute("Error", "Session has ended. Please login.");
        RequestDispatcher rd = request.getRequestDispatcher("C.jsp");
        rd.forward(request, response);
................The same code is in A.jsp and B.jsp. If I want to use the javascript to check if it's the top frame or not and redirect properly where exactly I need to put that code.
Thanks