>Or, are you trying to run some long-running process and think it would
>be better off as it's own thread? If that's the case, you probably want
>to look into some sort of queueing mechanism with either status polling
>or some sort of callback when the task is complete. Again, more details
>would be helpful.

No my process is not time consuming. It will finish in milliseconds and in the worst case can take a few seconds. I am not spawning a thread from each servlet request, but the request processor is another independent thread(started at web init) proecssing a queue of requests. I am only putting the request into the queue from doGet(). After putting into queue, the doGet() returns. The request processor thread then forms the response and tries to flush the output later. My experience is, sometimes I get the output in the browser, sometimes not. I thought it was a broser catching problem (I am not sure..).
I cant do a polling in the servlet, bacause it will block my servlet.

Has there any way to implement asynchronous request/response using servlets?

thanks and regards
Santhosh




---------------------------------------------------------------------
Couple of things...

No, I don't believe you can do anything with request/response after you
exit doGet(). Well, let me amend that... you MIGHT be able to get away
with it, but I wouldn't expect it to work all the time. What I mean is,
once your servlet is done it's work, the container takes over again, and
even if you do have a valid reference to the object, I wouldn't expect
that you could make any safe assumptions about the state of that object.
You might get away with it sometimes, but probably not every request.

The other point I wanted to make is that there is a pretty standard rule
against spawning threads to service requests. Simply stated, you aren't
supposed to do it. The container is supposed to spawn threads as
appropriate to service requests, and if your doing it on your own you
are more or less "competing" with the container. Bad Things (tm) tend
to happen under those circumstances.

I'm not really sure what you are trying to accomplish, but I'm taking a
guess that you think that by spawning the threads you will be able to
handle more requests concurrently. If that's not the case, please
explain you goals further.

But, assuming that is correct, I think you may have a fundamental
misunderstanding at work... A servlet is supposed to be thread-safe, and
the reason for that is that the container will spawn as many instances
of it as needed to service requests (to whatever configured limits there
are of course). In other words, every request essentially has it's own
thread executing your servlet, hence the need for it to be thread-safe.

In other words, you spwaning threads is superfluous because the
container is already doing essentially what your trying to do on your
own. So, just make sure your code is thread-safe, and your fine.

Or, are you trying to run some long-running process and think it would
be better off as it's own thread? If that's the case, you probably want
to look into some sort of queueing mechanism with either status polling
or some sort of callback when the task is complete. Again, more details
would be helpful.

As I said, I'm making assumptions here, so I could be completely wrong!

--
Frank W. Zammetti
Founder and Chief Software Architect
Omnytex Technologies
http://www.omnytex.com

Santhosh Thomas wrote:
>
>
> Hi
>
> I know this is a basic question. I am passing the request and response object to another thread from the doGet() and after that the Get method returns. So that the processing is done in the thread and response to client will be flushed later. But by that time the servlet method would have returned. My question is, is it possible to flush the output to the client even after the servlet method returned (or response is commited) by tomcat. I am not talking about any server push but it is a simple http question.
>
> If http does not support this, how can I implement this? can i do this by extending the generic servlet instead of HttpServlet?
>
> Any help is greatly appreciated
>
> thanks and regards
> Boolee