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copied!<p>I am assuming the existing session times out on the server before a request is received, and not because user logged out.</p> <p>Since the session will be deleted and its data lost, you have to make a copy of the session data in order to allow automatic "session continuation".</p> <p><strong>NOTE</strong> Untested code, just an idea.</p> <p>The idea is to watch for <code>HttpSessionListener.sessionDestroyed()</code> event:</p> <pre><code>class SessionDataBackupListener implements HttpSessionListener { private Map<String,Object> oldSessions = new HashMap<String,Object>(); public void sessionDestroyed(HttpSessionEvent event) { final Session s = event.getSession(); if (s.getAttribute("logOut")) { // Session was closed on-command, nothing to do. return; } // Session (probably) timed-out. Object sessionData = extractSessionData(s); // This should go into some kind of singleton DAO object. oldSessions.put(s.getAttribute("uniqueId"), sessionData); } } </code></pre> <p>Your log-out handler would look like:</p> <pre><code> public void logOut(HttpServletRequest req) { final Session s = req.getSession(); final String userId = s.getParameter("userId"); // Log the user out. // Mark the session was closed on-command. s.setAttribute("logOut", Boolean.TRUE); } </code></pre> <p>Your log-in handler would look like:</p> <pre><code> public void logIn(HttpServletRequest req) { final String uniqueId = s.getParameter("uniqueId"); Session s = req.getSession(false); // User returning after time-out? if (s == null && uniqueId != null) { // Create new session... s = req.getSession(true); // ...assign it the same uniqueId... s.setAttribute("uniqueId", uniqueId); // ...and put back old session data. copyDataToSession(s, getOldSessionData(uniqueId)); } else { // User logging in as usual. } } </code></pre> <p><code>getOldSessionData(final String uniqueId)</code> would look up the singleton DAO object for earlier session.</p>

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