A look at the latest jUnit (v3.7 ?) sources reveals that jUnit's classloader fails to use the correct Java 2 classloader delegation pattern. Instead of delegating to the parent classloader, whichever that might be, jUnit always delegates to the application classloader (through findSystemClass()). This is guaranteed to cause problems when jUnit is loaded by anything other the standard application classloader -- precisely the case when junit task is not forked by Ant, I believe.
Specifically, because Ant's install does not require lib/crimson.jar to be added to CLASSPATH or -classpath [namespace managed by the application classloader], it must be true that all classes in lib/ are loaded by Ant's own classloader (including org.xml.sax.InputSource). If the user installed another jar containing SAX classes in <jdk home>/jre/lib/ext the following scneario may happen:
- junit code needs to access SAX classes;
- junit asks its own classloader for those and the classloader delegates to the application classloader, which delegates to its parent, extension classloader [note that this completely bypasses Ant's classloader];
- we thus have two different classloaders acting as defining classloaders for the same SAX classes. It would have worked in Java 1.1 but in Java 2 this is precisely the 'violation of classloader constraints' problem that can be so hard to debug.
This is clearly a bug/flaw in jUnit framework and should be logged as such. I am a novice Ant user but I helped a co-worker track a classloader-related problem with Ant some months ago. At the time Ant had a similar problem with classlaoder delegation but I noticed that 1.4beta2 implementation was fixed. If jUnit classloader gets fixed as well, the two may actually work together inside the same JVM instance...
Vlad.
Please respond to [EMAIL PROTECTED]
To: <[EMAIL PROTECTED]>
cc:
Subject: Re: Class org/xml/sax/InputSource violates loader constraints
You will need to fork your junit task.
Conor
----- Original Message -----
From: "Atherton Richard - Z9V" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, August 28, 2001 11:52 PM
Subject: Class org/xml/sax/InputSource violates loader constraints
>
> I am using the Ant Junit task, running a single suite using the textui.
Has
> anybody come across the following when using the Ant Junit task? Either
the
> Ant or the JUnit class loader seems to be complaining about the
InputSource
> class inside 'xerces.jar'. (We get the problem when using the JUnit Swing
> GUI outside of Ant, which has a dynamic class loader).
>
> Cheers,
> Richard.
>
