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2.3 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，用代码清单2-1的内容发送消息，这个示例代码是以Sync方式发送消息的。
代码清单2-1 Producer示例程序
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DefaultMQPushConsumer类实现的消费者程序，如代码清单2-2所示。
代码清单2-2 Consumer示例程序
/＊
＊ 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<MessageExt>
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。