JPA and EJB3 Caveats - I

javax.persistence.PersistenceException: [PersistenceUnit: UnitName] class or package not found

WARN [ServiceController] Problem starting service persistence.units:ear=

If you get the above warning followed by the exception in the title, check your persistence.xml, some of the entity classes maybe declared wrong (e.g. point to wrong package).


JPA/EJB 3 Setup on Eclipse

Make sure that the persistence.xml file is located in the META-INF of the EAR Project.
Having it in your JPA project does NOT automatically propogate this file to where it needs to be.