Need to detect window event for applet

Question

I have an applet that needs to communicate with a servlet telling the servlet to logout once the parent window (web browser) is closed. I am new to programming with GUI's involved so I apologize for any ignorance. I have been searching for an answer on solving this problem for a while and have so far been able to write a simple applet that sends a message back to the servlet once the browser is closed by implementing the stop() function -- however it sends the same message when the back button is pressed. I need to message to be sent only when the browser is closed out.

Answer 1

Applets aside, there is no way to tell the server
when the remote user closes their browser. That’s
just one of the pits falls of web applications.
Now, in your applet, if it's possible to catch some
sort of window closing event when the browser closes
(and keep in mind I don't know if this is even
possible) then in the applets closing event you may
be able to use a URL object to post to your Servlet.That is what I was hoping to achieve -- I had defined my own stop() method which sent out a logout request to the servlet using the URL object... but it gets called every time a new page is requested. I also tried doing this in the destroy() method after reading that stop() should be called whenever a new page is requested to pause execution and that destroy() should be called when the object is reclaimed. This does not work how I expected in IE as it gets called each time a new page is requested -- must be destroyed and recreated every time.
In the URL you can pass some type of ID that uniquely
identifies your user. When the Servlet receives the
request from the applet you can parse out the ID from
the request and invalidate the users session,
essentially logging them out.I don't have to worry about a unique ID as this servlet only serves a single user at a time -- on first connection it locks the servlet and will report to other users that it is busy.
One other possible solution that I just found is the
following:
<script language="javascript">
window.onbeforeunload = function (evt) {
var message = 'Are you sure you want to leave?';
if (typeof evt == 'undefined') {
evt = window.event;
if (evt) {
evt.returnValue = message;
return message;
</script>This JavaScript function catches the window closing
event. From this function you would have to use the
JavaScript XMLHttpRequest object to send an
asynchronous request to your servlet (read up on
AJAX). Again, in the request you would need to pass
your ID to uniquely identify the user that you want
to log out.I will have to look at this -- although I want to do this in an applet that does not mean that would be the only solution that exists.
Either way it&#8217;s not going to be simple. Cheers.
-S