code: protected EntityManager getTransactionalEntityManager(EntityManagerFactory emf)
              throws IllegalStateException {
          Assert.state(emf != null, "No EntityManagerFactory specified");
          return EntityManagerFactoryUtils.getTransactionalEntityManager(emf);
      }
docs: Obtain the transactional EntityManager for this accessor's EntityManagerFactory, if any.
  
  @return the transactional EntityManager, or <code>null</code> if none
  @throws IllegalStateException if this accessor is not configured with an EntityManagerFactory
  @see
  EntityManagerFactoryUtils#getTransactionalEntityManager(javax.persistence.EntityManagerFactory)
  @see
  EntityManagerFactoryUtils#getTransactionalEntityManager(javax.persistence.EntityManagerFactory,
  java.util.Map)