code: protected Session getProducerSession() throws JMSException {
          if (producerSession == null) {
              synchronized (this) {
                  if (producerSession == null) {
                      producerSession = createSession(Session.AUTO_ACKNOWLEDGE);
                  }
              }
          }
          return producerSession;
      }
docs: Get the {@link Session} dedicated for sending messages.
  
  @return
  @throws JMSException