The jBPM ProcessClassLoader defines classes from within the par file but it does not define the associated package information.

As a consequence the result of <class>.getPackage() is null and code which relies on this (such as JAXB for package annotations) will not work.

A simple fix would be to add the following to the findClass method although it should be noted that this ignores the manifest/sealing information.

if (fileDefinition!=null) {
// Add the package information
final int packageIndex = name.lastIndexOf('.') ;
if (packageIndex != -1) {
final String packageName = name.substring(0, packageIndex) ;
final Package classPackage = getPackage(packageName) ;
if (classPackage == null)

}

With this fix in place the JAXB marshalling works as expected.