Java发送/接收消息示例

        可以用自己熟悉的开发工具创建一个Java项目，加入RocketMQ Client包的依赖，示例程序1的内容发送消息，这个示例代码是以Sync方式发送消息的。

示例程序1：

public class SyncProducer {
    public static void main(String[] args) throws Exception {
        //Instantiate with a Producer group name.
        DefaultMQProducer Producer = new
            DefaultMQProducer("please_rename_unique_group_name");
        producer.setNamesrvAddr("192.168.100.131:9876");
        //Launch the instance.
        Producer.start();
        for (int i = 0; i < 100; i++) {
            //Create a Message instance, specifying Topic, tag and Message body.
            Message msg = new Message("TopicTest" /* Topic */,
                "TagA" /* Tag */,
                ("Hello RocketMQ " +
                    i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
            );
            //Call send Message to deliver Message to one of brokers.
            SendResult sendResult = Producer.send(msg);
            System.out.printf("%s%n", sendResult);
        }
        //Shut down once the Producer instance is not longer in use.
        Producer.shutdown();
    }
}

主要流程是：创建一个DefaultMQProducer对象，设置好GroupName和NameServer地址后启动，然后把待发送的消息拼装成Message对象，使用Producer来发送。接下来看看如何接收消息，也就是使用DefaultMQPush-Consumer类实现的消费者程序，如示例程序2所示。

示例程序2：

       /*
         * Instantiate with specified Consumer group name.
         */
        DefaultMQPushConsumer Consumer = new DefaultMQPushConsumer("please rename to unique group name");
        /*
         * Specify name server addresses.
        Consumer.setNamesrvAddr("192.168.249.47:9876");
        /*
         * Specify where to start in case the specified Consumer group is a brand new one.
         */
Consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
        //Consumer.setMessageModel(MessageModel.BROADCASTING);
        /*
         * Subscribe one more more Topics to consume.
         */
        Consumer.subscribe("TopicTest”, "*");
        /*
         *  Register callback to execute on arrival of Messages fetched from brokers.
         */
        Consumer.registerMessageListener(new MessageListenerConcurrently() {
            public ConsumeConcurrentlyStatus consumeMessage(List msgs,   ConsumeConcurrentlyContext context) {
                System.out.printf(Thread.currentThread().getName() + " Receive New Messages: " + msgs + "%n");
                return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
            }
        });
        /*
         *  Launch the Consumer instance.
         */
        Consumer.start();
 

Consumer或Producer都必须设置GroupName、NameServer地址以及端口号。然后指明要操作的Topic名称，最后进入发送和接收逻辑。