code: public void send(MessageBuilder builder, SendMessageCallback cb, long timeout, TimeUnit unit) {
          Message msg = builder.build(this.messageBodyConverter);
          final String topic = msg.getTopic();
          MessageProducer producer = this.getOrCreateProducer(topic);
          producer.sendMessage(msg, cb, timeout, unit);
      }
docs: Send message asynchronously with callback.
  
  @param builder
  @param cb
  @param timeout
  @param unit
  @since 1.4.5