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From "Bill Barker" <billwbar...@verizon.net>
Subject Re: Tomcat threads
Date Wed, 03 Mar 2010 03:21:56 GMT


"Caldarale, Charles R" <Chuck.Caldarale@unisys.com> wrote in message 
news:99C8B2929B39C24493377AC7A121E21F96CB817BE5@USEA-EXCH8.na.uis.unisys.com...
>> From: Bharath Vasudevan [mailto:bharath.cng@gmail.com]
>> Subject: Re: Tomcat threads
>>
>> If we get a request on a thread, let some other thread do
>> the work for it and store the response info. The thread
>> which does the work writes the response on that request.
>
> If the processing is fast, why would you go to the complexity and overhead 
> of switching to another thread to process the request?
>
> You should also read the servlet spec, in particular SRV.2.3.3.3:
>
> "Implementations of the request and response objects are not guaranteed to 
> be thread
> safe. This means that they should only be used within the scope of the 
> request handling
> thread.
>
> "References to the request and response objects should not be given to 
> objects
> executing in other threads as the resulting behavior may be 
> nondeterministic. If
> the thread created by the application uses the container-managed objects, 
> such as
> the request or response object, those objects must be accessed only within 
> the
> servlet's service life cycle and such thread itself should have a life 
> cycle within
> the life cycle of the servlet's service method because accessing those 
> objects
> after the service method ends may cause undeterministic problems."
>
> The illogical behavior you're asking for simply isn't allowed.
>

At least not until Tomcat 7 ;).  In there, you can do exactly what the user 
is asking for using the AsyncContext.  The details are in the Servlet 3.0 
spec, but basically the request is handed off to another thread and the 
original one returns to the pool.  This also allows for two-way 
communication instead of relying on polling.

Of course Comet offers similar functionality in Tomcat 6 if you don't mind 
being bound to Tomcat.

> - Chuck
>
>
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