I was facing the following error when starting my EJB application in IBM WebSphere Application Server WAS 7.
JPAPUnitInfo E CWWJP0015E: An error occurred in the org.hibernate.ejb.HibernatePersistence persistence provider when it attempted to create the container entity manager factory for the *YOUR_PERSISTENCE_UNIT* persistence unit. The following error occurred: [PersistenceUnit: *YOUR_PERSISTENCE_UNIT*] class or package not found
While this error message may be unnoticed during startup, at the latest when you try to get your entity manager, you will see this error:
javax.ejb.EJBException: Injection failure; nested exception is: java.lang.IllegalStateException: EntityManagerFactory has not been created for PU : PuId=
The error message is similar for different error scenarios, so you find a lot of solutions in the web, but none of them may fit.