Auto Log Off once the session expires

Question

Our application logs off after 30 min and gets redirected to login page,i am specifying session timeout in web.xml and using a requestProcessor for redirecting.I want to show to the user a message saying your session got expired once the session expires,how can i do that.Auto log off ? I wuold like to prompt the error message on the page"The session is timout, please login again" . Then how could I detect the session is timeout? will any methods trigger automatically?

Answer 1

If you're using servlet sessions, you can check to see if the session the jsp / servlet is returning is new using the isNew() method. If yes, then the user's session has expired and you can display the relevant messages.

Answer 2

Create a Listener class implementing HttpSessionListener and define it in web.xml

This will notify you when any session is destroyed. Use the sessionDestroyed() method.

See a full example here:

http://www.mkyong.com/servlet/a-simple-httpsessionlistener-example-active-sessions-counter/

Answer 3

Include a javascript utility function inside your JSP and ping the server every 31 minutes. The above mentioned utility function should be using setTimeout() JS function internally.

setTimeout ( "checkServerSession()",  /* intervalInMilliSeconds */ 31000);

Note that

checkServerSession()

is a regular JS function which may fire HTTP requests. If the request is successful session exists otherwise show the prompt to the user.

Answer 4

You can use Servlet's HttpSession#getMaxInactiveInterval() to get the remaining lifetime of the current session and you can use JavaScript's setTimeout() to timeout a function callback.

1 + 1 = 2, so here's a basic example which needs to be placed inside a JSP (so that the EL, those ${} things, can do its work):

<script>
    setTimeout(function() {
        alert('Your session is timed out!'); // Display alert.
        window.location = 'logout.jsp'; // Then redirect to logout page.
    }, ${pageContext.session.maxInactiveInterval} * 1000); // It returns seconds, but setTimeout expect milliseconds.
</script>