ut.begin();
      InitialContext context = new InitialContext();
      EntityManagerFactory containerEmf = (EntityManagerFactory) context.lookup("java:comp/env/Cibet");
      EntityManager entityManager = containerEmf.createEntityManager();
      Resource res = new JpaResource();
      entityManager.persist(res);
      ut.commit();

      try {
         entityManager.joinTransaction();
      } catch (TransactionRequiredException e) {
         log.info("... but cannot join transaction: " + e.getMessage());
      }

      ut.begin();

javax.transaction.NotSupportedException: Nested Transactions are not supported
	at org.apache.geronimo.transaction.manager.TransactionManagerImpl.begin(TransactionManagerImpl.java:157)
	at org.apache.geronimo.transaction.manager.TransactionManagerImpl.begin(TransactionManagerImpl.java:152)