如何在JavaScript会话超时结束之前警告用户？

Question

I am coming to a minor problem where I have a session timeout in my web.xml for 15 minutes. But, in javascript I tried to warn the user for 5 minutes before it hits 15 minutes, but when it warns the user and the user clicks on OK, then the web app won't work anymore. All I want to do is warn the user about there session timeout and then when they press ok, they can still use the web app. Yet, when there session timeout times up, I want them to click on OK and takes them to a different web page. Thank you for the help.

Answer 1

First things first: When you want to warn the user 5 minutes before the 15 minutes timeout, the warning shoud be displayed at 10 minutes after page load.

setTimeout( function() { alert("Your session will expire in 5 minutes."); }, 10*60*1000);

If you want to redirect the user after 15 minutes to a different page, you don't actually need the user to confirm this.

setTimeout(function() {
    window.location = "timeout.xhtml";
}, 15*60*1000); 

So, when does the timeout actually happen?

With multiple tabs your user could just use the app in 2 tabs. The actions in the second tab will keep the app from timing out. One way is to reload the page and let the server handle the timeout and redirection part. Another option (preferred one) is to periodically check, whether the session still exists. Be aware: Your session checking should not extend the timeout period.