javascript and session info

[sudeshna de]

i want to find out whether my session has timed out or not by using java script.and finally how much time is left for timeout and that i want to show as an alert.please help me with some code if possible..
[ March 01, 2006: Message edited by: Bear Bibeault ]

[Bear Bibeault]

Sorry. It is not possible.

Also, please be sure to use descriptive subject titles. I have taken the opportunity to change this one for you.

[Stefan Evans]

Well its not directly possible, but you could do something like this on every page.

<script language="javascript">
var sessionTimeout = new Date( new Date().valueOf() + <%= session.getMaxInactiveInterval() %>);
</script>

You now have a javascript variable representing the date/time when the session on the server will expire.
You can use the javascript window.setTimeout or window.setInterval methods to call javascript after a certain amount of delay.
I'm sure you can figure out the rest from here.
[ March 02, 2006: Message edited by: Stefan Evans ]

[Bear Bibeault]

Except that the act of polling the session in this way resets the session timeout, making it ineffective for determining how much time is left on the session timeout.

I assumed that the OP was more interested in determining the amount of time remaining in the session as a result of user events on the page rather than at page load time when the answer will always be the length of the session timeout itself.

[Stefan Evans]

Sorry, guess I didn't make it clear.
Agreed: any access to a page resets the session timeout.

What I am suggesting is that you load into a javascript variable, the info you need to predict approximately when the session will time out
That being the maxInactiveInterval of the session.

Given this value in a javascript variable, you can perform javascript calculations as required. eg

// create javascript variable at time of page loading.
var sessionLength = <%= session.getMaxInactiveInterval() %>;
// set a timeout for (session length - 1 minute) to alert the user. window.setTimeout(alertSessionExpiring(), (sessionLength - 60)*1000 );

If the user does not navigate off this page, it should call the javascript alertSessionExpiring() method approximately a minute before the session would expire. The user can then take action to keep their session alive (ie make a request)
[ March 02, 2006: Message edited by: Stefan Evans ]