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From "Craig R. McClanahan" <>
Subject Re: WEB-INF/lib and .jar files in Tomcat 3.1
Date Thu, 01 Jun 2000 15:09:29 GMT
Jason Rumney wrote:

> Nacho <> writes:
> > I think that there are no restrictions to this, only that zip files are
> > no loaded from WEB-INF/lib, but a zip file is not jar :-).
> >
> >
> > > The reason I ask is that the CORBA libraries required by myapp do not
> > > appear to be loaded from myapp/WEB-INF/lib. I wonder whether they are
> > > too low-level for this method to work.
> > >
> >
> > i dont know, but until now everytime i have the feeling that tomcat
> > don't load a file from WEB-INF/lib was my fail no a Tomcat's fail.....
> Thanks for confirming that this should work, and I am not reading the
> servlet spec wrong.
> The files are jar files, and they are in WEB-INF/lib, not a
> subdirectory. Permissions are 664, so Tomcat should have no problems
> reading them. They are loaded if I place them in jakarta-tomcat/lib,
> but for reasons of organization I would prefer to keep them with the
> app rather than the server.
> The only thing I can think of is that these libraries contain
> org.omg.CORBA.* classes, so they may need to be loaded when the JVM
> starts up, to avoid clashes with the standard Java 1.2 classes. I don't
> know enough about the Java classloader to know whether this would be
> an issue, or if there is another problem.

That is going to be an issue.

As currently implemented, the class loader used by Tomcat looks on the system
classpath first, and then into the application-specific stuff (WEB-INF/classes
and WEB-INF/lib/*.jar).  Thus, the classes from the JDK are going to be found
where they have the same name, but the ones from your library will be found
when they are different -- a mix that probably isn't going to work.

IMHO the class loader logic should be reversed - load from the application
repositories first and then the system classpath.  I'm cross posting this to
the developer's list in order to discuss this further.

> --
> Jason Rumney <>
> AT&T Labs (Redditch, UK)

Craig McClanahan

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