"Heinemann, Andreas" wrote:
> Hi,
>
> i've got a question/problem concerning the doPost() method.
>
> As far as I know, whenever there is a new request, tomcat creates
> a new thread running through the doPost() method.
This is not precisely correct in all circumstances. In both Tomcat 3.2 and 4.0,
threads are pooled and re-used, rather than being created every time, for
performance reasons.
> Inside this
> method, my code does nothing special. But is passes the request and
> response objects to a queue. this queue is managed by other threads.
> then doPost() finishes.
>
> My question is: What happens to the request response objects when
> doPost() ends?
>
> It looks to me, that tomcat does some kind of cleanup, especially
> doing something with the stream objects attached to the
> request/response objects.
>
All versions of Tomcat recycle the request and response objects that were used
by a previous doPost() or doGet(). When these objects are re-used, the input
and output streams get attached to the new request's TCP/IP socket. Note that
this re-use might be on the same thread, or might be on some other thread.
As a consequence of this, you are not allowed to maintain a reference to the
request or response objects outside the scope of the current request processing
(i.e. the call to your doGet() or doPost() method).
>
> I've outlined some code in the 'first scenario' and got unexpected
> behavior. Seldom there occurs no error. Most of the time a client, who
> is reading the response, gets an java.io.StreamCorruptedError.
> Sometimes it is an java.io.EOFException.
>
> In the 'second scenario', I block the doPost()-thread, therefore making
> sure,
> that the request and response objects are still there and valid.
> Now there is no such problem.
>
> Any ideas?
>
Yep. Scenario 1 is illegal and will generate undefined results that differ
depending on which servlet container you run them in.
Scenario 2 illustrates why your approach is redundant anyway -- all you are
doing is adding extra overhead. Let the servlet container worry about threads,
and have your servlets concentrate on creating the responses.
>
> thanks, andreas
>
> ps: i'm using tomcat 3.1 and java 1.3 under winNT
>
You should really really really upgrade to 3.2. There are lots of bugs that
have been fixed, and performance is improved as well.
Craig McClanahan
