public void createOrderWithDAO_JTA() {
  
  Exception caught = null;

  /*
   * This DAO expects the caller to demarcate the transaction using JTA.  This DAO access database1.
   */
  WarehouseDAO dao1 = MyDAOFactory.getWarehouseJTA_DAO();

  /*
   * This DAO expects the caller to demarcate the transaction using JTA.   This DAO access database2.
   */
  OrderDAO dao2 = MyDAOFactory.getOrderJTA_DAO();

  /*
   * This publisher publishes messages to a JMS Topic  and expects the caller to demarcate the transaction. 
   * When creating session, make sure it is transacted.
   */  
  MessagePublisher publisher = null;

  UserTransaction utx = ResourceManager.getUserTransaction();

  try {
    /*                                                      
     * Execute the transaction. 
     * This transaction accesses three resources:
     *   1) a JMS Topic. 
     *   2) two different JDBC DataSources.
     */

    utx.begin();

      dao2.createOrder(....);

      dao1.updateWareHouse(....);

      publisher.publishTextMessage("Order Confirm Message....");

    utx.commit();

  } catch (Exception ex) {
    log.error(ex);
    caught = ex;
    if (utx != null) {
      try {
        utx.rollback();
      } catch (SystemException sysex) {
        log.error(sysex);
      }
    }
  } finally {
    if (dao != null) {
      dao.close();
      dao = null;
    }
    if (publisher != null) {
      publisher.close();
      publisher = null;
    }
    if (caught != null) {
      throw new DAORuntimeException(caught);
    }
  }
}

.....
In dao implementation:  
 conn = DBUtil.getXADBConnection();
 .....