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From "Noel J. Bergman (JIRA)" <server-...@james.apache.org>
Subject [jira] Commented: (JAMES-418) Loader uses wrong method to obtain class loader/doesn't set context class loader
Date Thu, 29 Dec 2005 15:33:04 GMT
    [ http://issues.apache.org/jira/browse/JAMES-418?page=comments#action_12361376 ] 

Noel J. Bergman commented on JAMES-418:
---------------------------------------

We spent years trying to get out from under an untagged version of Avalon that no one was
quite sure what was in it.  I do not want to see that again.  An SVN tag is a trivial thing
to do, and simply ensures that we have a clue as to what code we are running.

I'll ping Peter Royal about it.

> Loader uses wrong method to obtain class loader/doesn't set context class loader
> --------------------------------------------------------------------------------
>
>          Key: JAMES-418
>          URL: http://issues.apache.org/jira/browse/JAMES-418
>      Project: James
>         Type: Bug
>   Components: James Core
>     Versions: 2.2.0
>     Reporter: Ben Lindahl
>     Assignee: Stefano Bagnara
>  Attachments: cornerstone-datasources-impl-2.1.jar, phoenix-trunk.zip
>
> I had difficulty loading resources from my classes directory.  In reviewing the Loader
source code, I see two problems:
> 1) It uses this.class.getClassLoader(), rather than the preferred/standard Thread.currentThread.getContextClassLoader().
 This is not a problem right now, as the Apache James developers have control over the entire
application, but could become a difficult bug to track down in the future.  In addition, as
soon as you start adding multiple class loaders, chaining class loaders with parents becomes
impossible (see next point) because it sets the same class loader as multiple parents.  In
the source code, all instances of this.getClass().getClassLoader() (or whatever.getClass().getClassLoader())
should be replaced by Thread.currentThread().getContextClassLoader()
> 2) The greater problem is that it does not call Thread.currentThread().setContextClassLoader(classLoader).
 This means that any code that uses the standard method Thread.currentThread().getContextClassLoader()
(as my code does) will not get the correct class loader, and thus will not be able to load
the appropriate resources.  In fact, I was getting the primary class loader, which only loads
the Phoenix Jar.  I had to add into my code the following (the class loader's parent is already
set):
> Thread.currentThread().setContextClassLoader(MyClass.class.getClassLoader());
> By the nature of Java class loaders, it is expected that the thread's Context ClassLoader
is always kept current, and that any new class loaders are added to the chain.  I think that
this change should be made in the Apache James source code.

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