A top tip for those of you doing JPA development within Netbeans or even without Netbeans, something I stupidly forgot to do was to clean build after editing the persistence.xml file!

This effectivly meant that my new Entity classes where not being picked up and the persistence provider (EclipseLink) was throwing its legs in the air!

So remember always recompile after changing the persistence.xml file to ensure your changes are noticed by the Java Persistence Api!