java.lang.LinkageError: Class javax/xml/namespace/QName violates loader constraints: definition mismatch between parent and child loaders

Reason:
QName.class exists in both j2ee.jar and some jar that was added to the project. A definition mismatch occurs when classloader load these QName classes.

Solution:
Remove QName.class file from the jars that you add to the project. (ie. stax-api-1.0.1.jar, xml-apis-1.3.04.jar)