FWIW, this question (perhaps in different guises) has come up many
times on this list (and on other servlet-related mailing lists I'm
on), and Nic's response here very nicely sums up the consensus "best
practices" answer (at least, my impression of it).
When he talks about "timeout", he is referring to the timeout feature
of sessions, which you have control over, and which you almost
certainly should use no matter what else you are doing.
On Thu, 15 Jun 2000, Nic Ferrier wrote:
> >>> Rakesh Rajendran <[EMAIL PROTECTED]> 15-Jun-00 5:30:58 PM >>>
>
> >How do i detect a window closing event of the browser
> >window so that i can pass control to a controller servlet?
>
> Ahhh... this is really hard.
>
> Within a browser you've got 3 potential interactive forces:
>
> 1. the user
> 2. JavaScript
> 3. some other executable content, eg: an applet
>
> Obviously 1. is not much good to you.
>
>
> 2. JavaScript can handle events like a window.close() but
> unfortunately the options JavaScript has for talking to a servlet are
> limited.
>
> JS has no network interface - it has to use the browser to connect to
> a servlet, ie: by submiting a form that points to the servlet.
>
> So you could set up an event handler on window.close() which submits
> a form that you've hidden in the document.
>
> I have to confess that I've never tried this and I'm not sure it will
> work (will the browser allow a SUBMIT when it's closing?)
>
>
> 3. is conceptually much better because JS can talk directly to it,
> asking it to send some notification. As long as the applet was
> downloaded from the same place you want to send the notification you
> can just use a URLConnection to connect to the servlet and send the
> message.
>
> Alternately you could do the same with the destroy method.
>
> Both methods are flakey however since JVMs in browsers are quite
> unreliable.
>
>
> >It would be great if somebody could come up
> >with other alternatives.
>
> My advice is "don't do it".
>
> If you design like this you're fighting against the web. The web is a
> massively distributed environment, it is just not designed to be used
> like a traditional LAN client server app (where what you are doing is
> normal).
>
> Often people feel that some sort of logout is necessary but session
> management is designed specifically to allow resources to timeout
> cleanly rather than being specifically brought down by a logout
> event.
>
>
> If you post the reason why you want to do this peeps on the list can
> probably suggest alternative design patterns or reassure you that what
> you're trying to do is not necessary.
Milt Epstein
Research Programmer
Software/Systems Development Group
Computing and Communications Services Office (CCSO)
University of Illinois at Urbana-Champaign (UIUC)
[EMAIL PROTECTED]
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