[jdom-interest] B-7's MANIFEST.MF and newer versions of Xerces = PROBLEMS!!!

[Jason Hunter]

It was our belief when adding that MANIFEST entry that it only affected
the JAR when used as:

java -jar jdom.jar

and wouldn't affect the JAR's behavior when just placed in the CLASSPATH
environment variable.  I think testing bore that out, too.  But this may
be different on different JVMs and on different systems, and perhaps
depending on usage.  For example:

http://www.onjava.com/pub/a/onjava/2001/06/26/ejb.html?page=2

Seems to imply the various Class-path entries should be combined in a
JDK 1.3 environment.

Does anyone know more about this?  What we're trying to do is let you
run "java -jar jdom.jar" and have it work, which requires at least some
parser be present.

-jh-

"Jan C. Zawadzki" wrote:
> 
> I've just spent several days tracking a nasty CLASSPATH problem created
> by an entry in the Beta 7 MANIFEST.MF entry.
> 
> Basically the current jdom.jar will try to load the version of xerces it
> ships with - which creates CLASSPATH positioning dependencies that are a
> PAIN to track down.
> 
> To fix:
> 
> in package/META-INF/MANIFEST.MF, third line:
> 
>  >  Class-Path: ../lib/xerces.jar xerces.jar
> 
> remove the ../lib/xerces.jar bit.
> 
> What makes this so evil is that the JVM's under Linux resolve symbolic
> links.  When an symbolic link to jdom.jar is placed in some project's
> lib directory, both Linux JVM's still load the ../lib/xerces.jar
> RELATIVE to the REAL jdom.jar file - hence forcing the load of the
> xerces file shipped with the jdom package.  If jdom.jar appears prior to
> the newer version of Xerces, bad things happen.
> 
> To be honest I don't understand the rationale for placing this line
> there in the first place.  If the user can put jdom's jar file in the
> classpath, they can also put xerces there.  Using the class-path entry
> in the manifest file hides classpath behaviour, and makes debugging
> related problems much harder...
> 
> Jan
> 
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