How to clear database entries on browser close in jsf? - spring

Question

In our application which makes
use of JSF/PrimeFaces, Spring and Hibernate once a user logs in, we set a flag in the DB until the user logs out from the application or the session expires. The problem is, we need to clear this flag in the DB even when he simply closes the browser without proper logout. To acheieve this, I have already tried jquery $window.unload and $window.bind functions which actually invokes some JS function which is associated with <p:remoteCommand> which in turn invokes a managed bean method to clear the DB. However, I later came to know this is not reliable and while testing also we saw the event was not firing consistently. How can I achieve the DB cleanup anyway?

Answer 1

Listening on browser close is not reliable. You can use beforeunload event for that, but this is not supported on every webbrowser the world is aware of and even disableable/spoofable/hackable by the enduser. Then we're not talking about the race condition during firing the ajax request: would the ajax request arrive in its entirety right before the browser is closed? More than often this is not the case and the browser close wins over the ajax request.
Just listen server side on session expiration instead.
#WebListener
public class MyHttpSessionListener implements HttpSessionListener {
#Override
public void sessionCreated(HttpSessionEvent event) {
// NOOP.
}
#Override
public void sessionDestroyed(HttpSessionEvent event) {
HttpSession session = event.getSession();
// Do your job here.
// ...
}
}
Note that this is also invoked when you explicitly invoke ExternalContext#invalidateSession() (or HttpSession#invalidate()) during programmatic logout.