Just an aside. Venkat, I would venture a guess that the reason for the 'bleeding of
data' was a correct operation of Java when it comes to multi-threaded applications. If
you are loading or using a resource and do not flank it with synchronize{}, indeed you
could see this kind of behavior. Using the SingleThread model basically removes the
multi-threading ability of that particular servlet, thus solving the problem. However,
it will cost you some 'latency' time in terms of getting the server to respond. If you
have too many users, they will start seeing "waiting for reply...." for longer periods
of time. Just an FYI.
You might take a close look at your servlet code and flank the areas using single
sources of data that are not servlet service() method specific (ie, you instantiate or
load the values within the servlet invocation itself rather than that of the service()
method. In addition, if you use these pieces of data within the service() or other
method, flank them with synchronize{} statements and the problem should be solved
without resorting to the SingleThread Model.
--Mike H
*********** REPLY SEPARATOR ***********
On 12/07/1999 at 11:14 AM Venkat Nimishakavi wrote:
>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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