Well, we can ask User not to click Submit button more number of times. (or
use Java Script as suggested).
But, in a real world scenario, what happens if a set of 50-75 users use
same servlet (almost at same point of time - may not be exact )
I faced similar scenario, when in single user mode, my Servlet works fine.
But, if more users (say 25 - 30) invoke the servlet while using the
application, the resultant HTML page is jumbled/messed up. I guess other
users data is getting displayed on some other's page (we called it in our
group as Bleeding of Data or Data Spill Over !!!) .
Then I implemented servlet as SingleThreadModel and the problem was solved.
I was able to repeat the problem by NOT implementing as SingeThreadModel.
So, I came to the conclusion that, same instance of Servlet is getting
multiple requests and it is unable to decide to send What to Where (i mean
which user).
Using SingleThreadModel, an instance of Servlet will process only one
request at a time and it is able to decide to send resultant page to which
user.
My application (it's an internal tool) is being pounded by 40-50 users and
it behaves perfect.
Using SingleThreadModel we get easy thread safety at the cost of increased
resource requirements (b'cause more servlet instances are created) and it
may result in degradation of performance. But I felt it's better than data
bleeding.
I tried the above mentioned scenarios on Java Web Server and WebLogic
server. Both behaved in similar fashion.
Thanks
Venkat
> -----Original Message-----
> From: Kevin Mukhar [SMTP:[EMAIL PROTECTED]]
> Sent: Tuesday, December 07, 1999 9:11 AM
> To: [EMAIL PROTECTED]
> Subject: Re: more threads write to the same result page
>
> No, SingleThreadModel won't solve this problem. The web server/servlet
> engine
> will still handle concurrent requests. The difference is that with
> SingleThreadModel, each request will be sent to a different instance of
> the
> servlet, rather than as a separate thread to the same instance.
>
> How to solve this problem? Don't click the "submit" button more times at a
> very
> fast speed. Seriously. Sure it's a problem if one of your user's does
> this, but
> it's a problem they've created themselves by doing something they
> shouldn't have
> done.
>
> One approach I've seen is to use JavaScript in the web page to set a flag
> when
> the submit button is clicked the first time. This flag is checked whenever
> submit is clicked, and subsequent clicks are ignored if the flag was
> previously
> set. This solution fails when the user clicks the stop button before a new
> page
> is received or if the response comes back in a new window.
>
> Kevin Mukhar
>
> Venkat Nimishakavi wrote:
> >
> > Try running your servlet in SingleThreadModel
> >
> > > -----Original Message-----
> > > From: Zou hua [SMTP:[EMAIL PROTECTED]]
> > > Sent: Wednesday, December 08, 1999 3:19 AM
> > > To: [EMAIL PROTECTED]
> > > Subject: more threads write to the same result page
> > >
> > > Hello all,
> > >
> > > I have a servlet that uses Cookies. When I click the "submit" button
> from
> > > the HTML page once, it works well. If I click this button more times
> at a
> > > very fast speed, then the returned page looks very strange. It seems
> there
> > > are more than one datastreams being writen in the same result page.
> > >
> > > I have checked my log file. it seems there is only one seesion
> associated
> > > with these clicks, of course, this is what I expected. But more than
> one
> > > servlets ( or threads) runs for these click, maybe each click is
> > > associated
> > > with one . Some of them can catch IOException and some of them catch
> > > NULLPointerException when they try to write to
> > > "response.getOutputStream()".
> > >
> > > How to solve this problem?
>
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