Re: multiple servlet instances?

[Jon Eaves]

Craig R. McClanahan wrote:

On Mon, 21 Oct 2002, Nick Wesselman wrote:

Date: Mon, 21 Oct 2002 18:07:42 -0500
From: Nick Wesselman <[EMAIL PROTECTED]>
Reply-To: Tomcat Users List <[EMAIL PROTECTED]>
To: Tomcat Users List <[EMAIL PROTECTED]>
Subject: Re: multiple servlet instances?

the book was actually referring to the case where isThreadSafe="false"
... it uses misleading wording, however.

"... you also need to be aware that, even if a JSP page sets the
isThreadSafe attribute to false, JSP implementations are still
permitted to create multiple instances of the corresponding servlet..."
(my emph)

"Web Development with Java Server Pages" by Duane Fields and Mark Kolb
... p. 62 ... I just got a fax of the page in reference to a question
from a client. Thanks for your help!

I would need one of the authors to substantiate where in the JSP specs
they see the support for the assertion that multiple instances are
allowed.  I cannot find any evidence to support this in the JSP 1.2
specification (which the current edition purports to cover).

Further, I'm *very* skeptical about any claim that multiple instances of
the servlet running behind your JSP page would actually provide any
performance benefits, even if it were allowed by the specification.

Servlet Specification p22-23
SRV2.2 Number of Instances
The servlet declaration which is part of the deployment descriptor of the web application containing the servlet, as described in Chapter SRV.13, “Deployment Descriptor”, controls how the servlet container provides instances of the servlet. For a servlet not hosted in a distributed environment (the default), the servlet container must use only one instance per servlet declaration. However, for a servlet implementing the
SingleThreadModel interface, the servlet container may instantiate multiple instances to handle a heavy request load and serialize requests
to a particular instance."

I took that section of the specification to mean that multiple instances
of servlets can be created iff the SingleThreadModel interface is implemented.

Of course, that's just a reading of the spec and I'm not part of that JSR
so I could be interpreting it incorrectly. I would be interested in a
clarification though.

Cheers,
-- jon

--
Jon Eaves <[EMAIL PROTECTED]>
http://www.eaves.org/jon/


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