Set transaction isolation to read-committed.

1. read a persistent entity
2. delete the row from the DB from another process
3. refresh the entity

The EntityManager throws:
org.hibernate.UnresolvableObjectException: No row with the given identifier exists: ch.logobject.test.model.TaskAlloc#686796
at org.hibernate.UnresolvableObjectException.throwIfNull(UnresolvableObjectException.java:42)
at org.hibernate.event.def.DefaultRefreshEventListener.onRefresh(DefaultRefreshEventListener.java:126)
at org.hibernate.event.def.DefaultRefreshEventListener.onRefresh(DefaultRefreshEventListener.java:39)
at org.hibernate.impl.SessionImpl.refresh(SessionImpl.java:694)
at org.hibernate.ejb.AbstractEntityManagerImpl.refresh(AbstractEntityManagerImpl.java:160)
at org.jboss.ejb3.entity.InjectedEntityManager.refresh(InjectedEntityManager.java:112)

According to the EJB3 specs the entity manager should throw a EntityNotFoundException. This should be an easy catch/wrap and rethrow fix.