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From "Lee, William" <William....@Cognos.COM>
Subject RE: Webapp classloader question.
Date Fri, 10 Oct 2003 16:04:53 GMT
It seems to me that we are going for "bandaid" solution here. By moving
around the files, it will work for one particular webapp, but at the
expensive of the compatibility of other webapp under the same tomcat. As
soon as we move the parser out of one webapp, we are forcing all other
webapp using the same parser, which I believed is not the right way to go.

Rather, why forcing the delegate model for these two particular packages
(xerces & xalan)? Isn't it true that the endorse mechanism only required
that the endorsed directory should be traverse before the system?

I still didn't see the reason how this "endorsed mechanism" has anything to
do with the servlet spec., and that it would force servlet container to skip
the one in webapps?

Thanks again.
William.


-----Original Message-----
From: Cox, Charlie [mailto:ccox@cincom.com] 
Sent: Friday, October 10, 2003 8:46 AM
To: 'Tomcat Developers List'
Subject: RE: Webapp classloader question.


you want to put the one from endorsed into server/lib, then put yours in
WEB-INF. This way only one is visible to any tree of the classloader. But
I'm not sure if you will still end up with the JDK version since the one in
WEB-INF is not "endorsed" to override it.

The other thing I would try is to put your version in /common/endorsed with
the tomcat version in /server/lib.

btw, have you just tried replacing the version in /endorsed with your newer
one?

Charlie

> -----Original Message-----
> From: Lee, William [mailto:William.Lee@Cognos.COM]
> Sent: Thursday, October 09, 2003 4:54 PM
> To: 'Tomcat Developers List'
> Subject: RE: Webapp classloader question.
> 
> 
> This won't work since, all jar files in commons/lib,
> commons/endorsed, and
> commons/classes are all visible to the tomcat's "commons" 
> classloader. So,
> there is no difference whether we put the xerces jar files in "lib" or
> "endorsed", the one from webapps will be skipped.
> 
> I think the question boiled down to, if we have Xerces on
> both "endorsed"
> and "webapps", which one should be used? For tomcat, I would 
> thought that
> the order for class searching will be "webapps", "shared", "commons"
> (including "endorsed"), then "system".
> 
> I believed tomcat put "endorsed" before "system" is to
> follows the "endorsed
> classloading spec.". But I also believed forcing delegate 
> model for xerces
> and xalan maybe overkill?
> 
> Indeed, the tomcat's "class-loader-howto" document also
> indicated that the
> one from webapps should be used instead.
> 
> Frankly speaking, I'm no expert on these topics, so please
> feel free to
> correct me if I mis-understanding anything here.
> 
> Thanks.
> William.
> 
> -----Original Message-----
> From: Shapira, Yoav [mailto:Yoav.Shapira@mpi.com]
> Sent: Thursday, October 09, 2003 12:44 PM
> To: Tomcat Developers List
> Subject: RE: Webapp classloader question.
> 
> 
> 
> Howdy,
> Tomcat 4.1.x implements the endorsed classloader spec.  It's
> compliant with
> the Servlet Specification v2.3.  What you can do if you want 
> your webapp to
> use the latest xerces/JAXP, is:
> - Move $CATALINA_HOME/common/endorsed/* to $CATALINA_HOME/common/lib
> - Put your later xerces etc. in WEB-INF/lib as you've been doing.
> 
> Yoav Shapira
> Millennium ChemInformatics
> 
> 
> >-----Original Message-----
> >From: Lee, William [mailto:William.Lee@Cognos.COM]
> >Sent: Thursday, October 09, 2003 12:38 PM
> >To: tomcat-dev@jakarta.apache.org
> >Subject: Webapp classloader question.
> >
> >
> >Hi all,
> >
> >I'm not sure if this message reaches you guys yet, so here
> it go again.
> >Sorry for any inconvenience if you receiving this message twice.
> >
> >Thanks.
> >William.
> >
> >-----Original Message-----
> >From: Lee, William [mailto:William.Lee@cognos.com]
> >Sent: Tuesday, October 07, 2003 3:55 PM
> >To: 'tomcat-dev@jakarta.apache.org'
> >Subject: Webapp classloader question.
> >
> >
> >Hi all,
> >
> >When moving from tomcat 4.0.x to 4.1.x, we discovered that the
> >WebappClassLoader.java had been changed such that all classes from 
> >"org.apache.xerces" and "org.apache.xalan" are forced to be loaded
> using
> >the
> >delegate model first, before looking into the webapp directory. This
> seems
> >to related to the JDK 1.4 support of the xml and xslt parser.
> >
> >However, after a long conversation with the Sun's Java engineer, he
> point
> >out that, even JDK 1.4 shipped with the default xml and xslt parser,
> >application server and servlet container should continue to 
> use the one
> >provided from the webapp directory as described in the servlet spec.
> 2.3.
> >
> >Could someone please hint some lights on why tomcat 4.1.x decided to
> >enforce the delegate model for these two packages?
> >
> >(The reason I'm asking is that, we try to use the latest
> Xerces in our
> >webapps, and since it always look and found the one from
> common/endorsed
> >directory, our latest version will always be skipped.)
> >
> >Thanks in advance for your help.
> >William.
> >
> >Join us at Cognos' biggest event of the year Enterprise 2003, The
> Cognos
> >Business Forum.  Taking place in over 25 cities around the
> world, it's
> an
> >opportunity for Business and IT leaders to learn about
> strategies for
> >driving performance. Visit
http://www.cognos.com/enterprise03 for more 
>details.
>
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Join us at Cognos' biggest event of the year Enterprise 2003, The Cognos
Business Forum.  Taking place in over 25 cities around the world, it's an
opportunity for Business and IT leaders to learn about strategies for
driving performance. Visit http://www.cognos.com/enterprise03 for more
details. 

This message may contain privileged and/or confidential information.  If you
have received this e-mail in error or are not the intended recipient, you
may not use, copy, disseminate or distribute it; do not open any
attachments, delete it immediately from your system and notify the sender
promptly by e-mail that you have done so.  Thank you.

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