rocketMQ发送消息入门

使用rocketmq发送消息、接收消息：
（1）引入client包
<dependency>
    <groupId>org.apache.rocketmq</groupId>
    <artifactId>rocketmq-client</artifactId>
    <version>4.2.0</version>
</dependency>
（2）在linux上启动NameServer、BrokerServer

（3）生产者
public class Producer {
public static void main(String[] args) throws Exception{
Producer p = new Producer();
p.sendMessage();
}

// 发送消息
void sendMessage() throws Exception {
DefaultMQProducer producer = new DefaultMQProducer("producer_test");
// 指定NameServer地址
producer.setNamesrvAddr("192.168.191.131:9876"); // 多个ip以分号分隔
/**
* Producer对象在使用之前必须要调用start初始化，初始化一次即可 注意：切记不可以在每次发送消息时，都调用start方法
*/
producer.start();
for (int i = 0; i < 20; i++) {
// 构建消息
Message msg = new Message("MyTopic", "Tag", ("hello " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
// 发送同步消息
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
producer.shutdown();
}
}

（4）消费者
public class Consumer {

public static void main(String[] args) throws Exception{
Consumer c = new Consumer();
c.receiveMessage();
}

void receiveMessage() throws MQClientException{
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer_test");
// 指定NameServer地址，多个地址以 ; 隔开
consumer.setNamesrvAddr("192.168.191.131:9876");
/**
* 设置Consumer第一次启动是从队列头部开始消费还是队列尾部开始消费 如果非第一次启动，那么按照上次消费的位置继续消费
*/
consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
consumer.subscribe("MyTopic", "*"); //MyTopic 跟生产者发送消息的Topic相同
consumer.registerMessageListener(new MessageListenerConcurrently() {
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
try {
for (MessageExt msg : msgs) {
String msgbody = new String(msg.getBody(), "utf-8");
System.out.println("接收消息: " + msgbody);
}
} catch (Exception e) {
e.printStackTrace();
return ConsumeConcurrentlyStatus.RECONSUME_LATER; //稍后再试
}
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS; //消费成功
}
});
consumer.start();
System.out.printf("consumer start..%n");
}
}

（5）问题
1.Exception in thread "main" org.apache.rocketmq.client.exception.MQClientException: No route info of this topic, MyTopic
Broker 禁止自动创建 Topic，且用户没有通过手工方式创建 Topic

nohup sh mqbroker -n localhost:9876 autoCreateTopicEnable=true &

关闭防火墙：service iptables stop