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From "Shapira, Yoav" <Yoav.Shap...@mpi.com>
Subject RE: Multiple requests sharing the same Servlet instance
Date Wed, 16 Jun 2004 13:17:35 GMT

Hi,
No, it doesn't mean one instance of a servlet class is created.  It
means the container is free to pool the instances any which way it
likes, optionally adjusting for load, destroying unused servlets to save
resources, etc.  The lifecycle of a servlet is not necessarily related
to its pooling, they address separate concerns.

You have a whole host of options for where to put temporary data used by
a servlet, as you do in general for java classes.  The design
considerations for synchronization are the same as whenever you design
an object that can be used by multiple threads concurrently.

Yoav Shapira
Millennium Research Informatics


>-----Original Message-----
>From: Keith Hankin [mailto:keithh@addr.com]
>Sent: Wednesday, June 16, 2004 9:14 AM
>To: Tomcat Users List
>Subject: Re: Multiple requests sharing the same Servlet instance
>
>So this means that only one instance of a given Servlet class is every
>created? How does one do any real work with this? Where do I put my
>temporary data if not in attributes of the Servlet instance? And what
is
>the
>reason for having a life cycle of Servlets, with init/destroy methods?
I
>thought it would use Servlet instance pooling.
>
>----- Original Message -----
>From: "Shapira, Yoav" <Yoav.Shapira@mpi.com>
>To: "Tomcat Users List" <tomcat-user@jakarta.apache.org>
>Sent: Monday, June 14, 2004 8:22 PM
>Subject: RE: Multiple requests sharing the same Servlet instance
>
>
>>
>> Hi,
>> I don't think your understanding is correct: the container may allow
>> multiple threads to use the same servlet instance concurrently.  If
you
>> need synchronization around or within that method, or around some
fields
>> in your servlet class, you are responsible for it.
>>
>> The container does guarantee that only one thread will process a
request
>> from start to finish, i.e. the same thread will invoke any filters,
>> servlets, etc. for the same request.
>>
>> Yoav Shapira
>> Millennium Research Informatics
>>
>>
>> >-----Original Message-----
>> >From: Keith Hankin [mailto:keithh@addr.com]
>> >Sent: Monday, June 14, 2004 10:53 AM
>> >To: Tomcat Users List
>> >Subject: Multiple requests sharing the same Servlet instance
>> >
>> >I am having a problem where one Servlet instance seems to being used
by
>> two
>> >different threads at the same time. It is my understanding that
Servlet
>> >instances will not be used by two threads at the same time, so that
the
>> >service() method would thus only be called by one thread, then it
can
>> be
>> >called again if the Servlet instance is reused by way of pooling.
>>
>>
>>
>>
>> This e-mail, including any attachments, is a confidential business
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>>
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>
>
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