code: @Override
     public void resume(Transaction tx) throws InvalidTransactionException, IllegalStateException, SystemException {
        if (trace) log.tracef("Resuming tx %s", tx);
        setTransaction(tx);
     }
docs: Resume the association of the calling thread with the given transaction.
  
  @param tx The transaction to be associated with the calling thread.
  @throws javax.transaction.InvalidTransactionException
  If the argument does not represent a valid transaction.
  @throws IllegalStateException If the calling thread is already associated with a transaction.
  @throws javax.transaction.SystemException
  If the transaction service fails in an unexpected way.