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Question

I have created a java login application in which all is working fine but when I click on logged out button it successfully logged out and redirect to index.jsp but in index.jsp page if I print session value then it is printing the same, I do not know why ?? However, on logged out I have kill the session. Below is the code, please suggest the possible reason:

on index.jsp page following is the code which is checking wheather session is exist or not. After logout it is printing "isession is not null"...

<%
            if (session == null) 
            {
                System.out.println("session is null");
                session.removeAttribute("username");
                session.removeAttribute("uniqueID");
                session.invalidate();
            }
            else if(session != null)
            {
                System.out.println("isession is not null");
                System.out.println(session);
            }

        %> 

loginServlet.java

String name = "";
            JSONObject obj = result_array.getJSONObject(0);
            String res = obj.get("result").toString();
            HttpSession session = null;
            if (res.equals("true")) {
                try {
                    name = obj.get("name").toString();
                    session = request.getSession(true);
                    session.setAttribute("username", name);
                    session.setAttribute("uniqueID", uname);
                    //setting session to expiry in 15 mins
                    session.setMaxInactiveInterval(15*60);
                    Cookie userName = new Cookie("user", uname);
                    userName.setMaxAge(15*60);
                    response.addCookie(userName);

                    if("0".equals(obj.get("role").toString()))
                    {
                        session.setAttribute("role", "user");
                        response.sendRedirect("home.jsp");                        
                    }                        
                    else if("1".equals(obj.get("role").toString()))
                    {
                        session.setAttribute("role", "admin");
                        response.sendRedirect("AdminHome.jsp");                        
                    }
                } 
                catch (JSONException ex) 
                {
                    System.out.println(getClass().getName()+" = " +ex.toString());
                    this.context.log(ex.toString());
                }

logoutservlet.java

protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
//        Cookie[] cookies = request.getCookies();
//        if (cookies != null) {
//            for (Cookie cookie : cookies) {
//                if (cookie.getName().equals("JSESSIONID")) {
//                    System.out.println("JSESSIONID=" + cookie.getValue());
//                    break;
//                }
//            }
//        }
        Cookie loginCookie = null;
        Cookie[] cookies = request.getCookies();
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                if (cookie.getName().equals("user")) {
                    loginCookie = cookie;
                    break;
                }
            }
        }
        if (loginCookie != null) {
            loginCookie.setMaxAge(0);
            response.addCookie(loginCookie);
        }
        PrintWriter out = response.getWriter();
        HttpSession session = request.getSession(false);
        if (session != null) {
            session.removeAttribute("username");
            session.removeAttribute("uniqueID");
            session.removeAttribute("role");
            session.invalidate();
        }
        out.print("You have Succefully logged out ");
        response.sendRedirect("index.jsp");
        out.flush();
        out.close();
    }
}

Answer 1

By default, a session is automatically created for a JSP unless it already exists of course. So, post-logout when you're checking for the implicit session object again, it's a new one.

You can verify this by printing

<%= session.isNew() %>

To turn this off for a particular JSP, you need set the session attribute of your page directive.

<%@ page session="false" %>

This seems unnecessary though because the logged-in/out state can always be determined by the presence of a session attribute rather than the nullity of the session itself.