Fixing Classloader Linking Errors

[Bendfelt, Tim (MED, nVisia, GEMS-IT)]

I have run into a dreaded Classloader linking constraint while executing
a junit task and need advice on which solution to pursue. Apparently the
root of the problem is the duplication of classpaths between the System
Classloader and "some other" Classloader. here is the Exception stack:

java.lang.LinkageError: loader constraints violated when linking
org/xml/sax/ContentHandler class
at com.client.Foo.<init>(Foo.java:67)
at com.client.test.FooTest.testBar(FooTest.java:43)
at java.lang.reflect.Method.invoke(Native Method)
at junit.framework.TestCase.runTest(TestCase.java:156)
at junit.framework.TestCase.runBare(TestCase.java:130)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:121)
at junit.framework.TestSuite.runTest(TestSuite.java:160)
at junit.framework.TestSuite.run(TestSuite.java:155)
at
org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTe
stRunner.java:209)
at
org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.executeInVM(JUnit
Task.java:409)
at
org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.execute(JUnitTask
.java:283)
at
org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.execute(JUnitTask
.java:263)
at org.apache.tools.ant.Target.execute(Target.java:153)
at org.apache.tools.ant.Project.runTarget(Project.java:898)
at org.apache.tools.ant.Project.executeTarget(Project.java:536)
at org.apache.tools.ant.Project.executeTargets(Project.java:510)
at org.apache.tools.ant.Main.runBuild(Main.java:421)
at org.apache.tools.ant.Main.main(Main.java:149)


I have attempted to run the junit with fork="yes", but this breaks some
other things and is not viable.
The junit test runs fine outside of the ant/junit target. (from command
prompt)

Any input would be appreciated. Here are two useful archive searches
that hint at the cause/solution:
http://marc.theaimsgroup.com/?l=ant-dev&w=2&r=1&s=loader+constraints+&q=
b
http://marc.theaimsgroup.com/?l=ant-user&w=2&r=1&s=loader+constraints&q=
b

Any discussion on this topic is bound to help as I am at a loss to
adequately dissect the problem.

Tim