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From "Cox, Charlie" <c...@cincom.com>
Subject RE: Webapp classloader question.
Date Fri, 10 Oct 2003 17:16:43 GMT
ok, I just found this link from the archives. Sun defined that you have to
use the 'endorsed' directory or take the Sun-supplied versions of the
packages listed.
http://java.sun.com/j2se/1.4.2/docs/guide/standards/index.html

tomcat's classloading is enforcing this requirement explicitly since it does
not delegate to the parent classloader first.

so you can only replace the version in /endorsed
Charlie

> -----Original Message-----
> From: Lee, William [mailto:William.Lee@Cognos.COM]
> Sent: Friday, October 10, 2003 12:05 PM
> To: 'Tomcat Developers List'
> Subject: RE: Webapp classloader question.
> 
> 
> 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
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> > >driving performance. Visit
> http://www.cognos.com/enterprise03 for more 
> >details.
> >
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> 
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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 
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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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