Hmm... (brain ticking)
When you press the stop button on a browser, chances are that the
browser has already send a request to a server and is waiting for a
response. Ofcourse you could also have pressed the stop button when the
browser is still issuing a request, but the time required for issuing a
request is much greater than the time required for waiting for the response.
(unless you have some huge POST data) .
So the maximum that you could hope for is that the servlet throws an
IOException when writing to the output stream. And then hope that the
exception was thrown because the client clicked the stop button. This is
loony logic because this IOException could be thrown for other reasons as
well, such as the connection getting lost or timed out.
I really dont believe that you could detect the stop button being
clicked. There is no event handler in JavaScript that detects the stop
button being clicked. (for very good reasons : - which is the script that
should detect it ? the one that got unloaded or the one that is loading ?)
You could get around this with some convoluted Javascript hacks that I
do not recommend. One such tactic is
that you could open a window with no stop buttons at all (and disable the
hot keys) so that the only way the user can stop the page from loading is to
close the window.
Another would be to have a hidden frameset in each page (width & height
=0) which has a script that monitors the activity of the links in the
visible frameset, and checks that the link that was clicked on was loaded.
This solution is more in the realm of DHTML than servlets and doesnt serve
much purpose apart from making simple things complicated.
About the cleaning up work, it depends on what volume of data you happen
to have associated for each user session. You can either set timeout
intervals for sessions or if you are reasonably sure that the client has
terminated his/her session, you could manually get rid of the data yourself.
You cannot "destroy" objects that are created within the servlets. At
maximum, you can set their references to null and hope that the garbage
collector collects them. If you are planning to destroy instance objects,
then thats dangerous, because an instance of a servlet could be assigned
multiple requests in different threads (unless you are using the
SingleThreadedModel)
I am actually quite confused as to what are you trying to do. Could you
give a brief explanation of what are you trying to achieve ? Maybe we can
accomplish it another way.
----- Original Message -----
From: "Sudarson_Pratihar" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, April 28, 2001 3:42 PM
Subject: Re: How to detect browser stop -- it is possible!
> Thanks for the reply. But what you have talked about the Browser closing ,
> I'm talking about the stop button(or interrupt) button of browser.
> Is that applicable for that also?
>
> And if so, how can I destroy the objects that are created within the
> particular servlet.
>
> Pls highlight on the clean up work.
>
> Regards,
> Sudarson
>
>
> > ----------
> > From: Tarun Ramakrishna Elankath[SMTP:[EMAIL PROTECTED]]
> > Reply To: A mailing list for discussion about Sun Microsystem's Java
> > Servlet API Technology.
> > Sent: Friday, April 27, 2001 8:36 PM
> > To: [EMAIL PROTECTED]
> > Subject: Re: How to detect browser stop -- it is possible!
> >
> > Well IT IS actually possible for the browser to inform the server that
it
> > has been closed.! You would have to do the scripting via JavaScript
> > though.
> > You could set a onunload() event handler for the window. This onunload
> > event
> > handler could then call a server-side script with the parameter
> > close=true.
> > The server-side script could then use this information to perform
> > some-clean
> > up operations. However the sever-side script SHOULD NOT write to the
> > client,
> > because by that time IE/NS would have closed the window down.
> >
> > A rough outline of how this works is like follows :
> >
> > <script language="javascript">
> > window.onunload = function() {
> > location.href="detect_close.jsp?close=true";
> > }
> > </script>
> >
> > You could do whatever you want in the JSP. Note that the JSP WILL KNOW
> > which
> > client has shut the window, because the browser would send the
> > session/cookie data in the request just before the window shuts down.
> >
> > ----- Original Message -----
> > From: "Kevin Mukhar" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Friday, April 27, 2001 7:56 PM
> > Subject: Re: How to detect browser stop
> >
> >
> > > Sudarson_Pratihar wrote:
> > > >
> > > > Is there any way to detect browser stop?
> > >
> > > No. It's been a while since we had this discussion here, but the
answer
> > > is still the same: the browser does not notify any server when the
> > > browser is stopped or exited. You might want to check the archives to
> > > review past discussions on this topic.
> > >
> > > > So that if a user clicks the
> > > > browser stop, the servlet at the server side can be destroyed.
> > >
> > > You don't want to do this anyway. The servlet is a server resource and
> > > should generally be available as long as the server is running. The
best
> > > way to deal with this situation is just to catch the IOException that
is
> > > thrown when the servlet tries to send the response to the client;
since
> > > the client no longer wants the response, there's really nothing else
to
> > > be done.
> > >
> > >
> >
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> > >
> >
> >
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