Java操作RockeMQ

RocketMQ是阿里巴巴在2012年开源的分布式消息中间件，目前已经捐赠给Apache基金会，已经于2016年11月成为 Apache 孵化项目，相信RocketMQ的未来会发挥着越来越大的作用，将有更多的开发者因此受益。

本文仅对RocketMQ的简单实用做入门性介绍，不对RocketMQ的底层原理进行深入介绍，后续文章将对RocketMQ的原理做详细介绍。

RocketMQ的Maven依赖：

<!-- https://mvnrepository.com/artifact/com.alibaba.rocketmq/rocketmq-client -->
<dependency>
    <groupId>com.alibaba.rocketmq</groupId>
    <artifactId>rocketmq-client</artifactId>
    <version>3.2.6</version>
</dependency>

MQ的消费类RocketMQConsumer.java：

package com.lance.rocketMQ.RocketMQ;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.MessageListener;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;

import java.util.UUID;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQConsumer {

    private DefaultMQPushConsumer consumer;

    private MessageListener listener;

    protected String nameServer;

    protected String groupName;

    protected String topics;

    public RocketMQConsumer(MessageListener listener, String nameServer, String groupName, String topics) {
        this.listener = listener;
        this.nameServer = nameServer;
        this.groupName = groupName;
        this.topics = topics;
    }

    public void init() {
        consumer = new DefaultMQPushConsumer(groupName);
        consumer.setNamesrvAddr(nameServer);
        try {
            consumer.subscribe(topics, "*");
        } catch (MQClientException e) {
            e.printStackTrace();
        }
        consumer.setInstanceName(UUID.randomUUID().toString());
        consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_LAST_OFFSET);
        consumer.registerMessageListener((MessageListenerConcurrently) this.listener);

        try {
            consumer.start();
        } catch (MQClientException e) {
            e.printStackTrace();
        }
        System.out.println("RocketMQConsumer Started! group=" + consumer.getConsumerGroup() + " instance=" + consumer.getInstanceName()
        );
    }

}

MQ消息的监听接口类RocketMQListener.java

package com.lance.rocketMQ.RocketMQ;

import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.common.message.MessageExt;

import java.util.List;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQListener  implements MessageListenerConcurrently {

    @Override
    public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
//        System.out.println("get data from rocketMQ:" + msgs);
        for (MessageExt message : msgs) {

            String msg = new String(message.getBody());
            System.out.println("msg data from rocketMQ:" + msg);
        }

        return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
    }
}

MQ消息的生产者类RocketMQProducer.java

package com.lance.rocketMQ.RocketMQ;

import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.client.producer.SendStatus;
import com.alibaba.rocketmq.common.message.Message;

import java.util.UUID;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQProducer {

    private DefaultMQProducer sender;

    protected String nameServer;

    protected String groupName;

    protected String topics;

    public void init() {
        sender = new DefaultMQProducer(groupName);
        sender.setNamesrvAddr(nameServer);
        sender.setInstanceName(UUID.randomUUID().toString());
        try {
            sender.start();
        } catch (MQClientException e) {
            e.printStackTrace();
        }
    }

    public RocketMQProducer(String nameServer, String groupName, String topics) {
        this.nameServer = nameServer;
        this.groupName = groupName;
        this.topics = topics;
    }

    public void send(Message message) {

        message.setTopic(topics);

        try {
            SendResult result = sender.send(message);
            SendStatus status = result.getSendStatus();
            System.out.println("messageId=" + result.getMsgId() + ", status=" + status);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

测试RocketMQ的消费 RocketMQConsumerTest.java

package com.lance.rocketMQ.RocketMQ;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQConsumerTest {

    public static void main(String[] args) {

        String mqNameServer = "172.10.254.2:9876";
        String mqTopics = "MQ-MSG-TOPICS-TEST";

        String consumerMqGroupName = "CONSUMER-MQ-GROUP";
        RocketMQListener mqListener = new RocketMQListener();
        RocketMQConsumer mqConsumer = new RocketMQConsumer(mqListener, mqNameServer, consumerMqGroupName, mqTopics);
        mqConsumer.init();

        try {
            Thread.sleep(1000 * 60L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}

测试RocketMQ的消费 RocketMQConsumerTest.java

package com.lance.rocketMQ.RocketMQ;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQConsumerTest {

    public static void main(String[] args) {

        String mqNameServer = "172.10.254.2:9876";
        String mqTopics = "MQ-MSG-TOPICS-TEST";

        String consumerMqGroupName = "CONSUMER-MQ-GROUP";
        RocketMQListener mqListener = new RocketMQListener();
        RocketMQConsumer mqConsumer = new RocketMQConsumer(mqListener, mqNameServer, consumerMqGroupName, mqTopics);
        mqConsumer.init();

        try {
            Thread.sleep(1000 * 60L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}

run RocketMQConsumerTest.java 之后，控制台输出：

RocketMQConsumer Started! group=CONSUMER-MQ-GROUP instance=1eb7d308-4414-4658-90b5-e2cae3b793eb

结果分析： 此时MQ对应的TOPIC中并没有响应的消息，故收不到消息，仅看到MQ消费者正常启动信息。

MQ的生产者测试类:RocketMQProducerTest.java

package com.lance.rocketMQ.RocketMQ;

import com.alibaba.rocketmq.common.message.Message;

/**
 * Created by lance on 2017/2/10.
 */
public class RocketMQProducerTest {

    public static void main(String[] args) {

        String mqNameServer = "172.10.254.2:9876";
        String mqTopics = "MQ-MSG-TOPICS-TEST";

        String producerMqGroupName = "PRODUCER-MQ-GROUP";
        RocketMQProducer mqProducer = new RocketMQProducer(mqNameServer, producerMqGroupName, mqTopics);
        mqProducer.init();

        for (int i = 0; i < 5; i++) {

            Message message = new Message();
            message.setBody(("I send message to RocketMQ " + i).getBytes());
            mqProducer.send(message);
        }

    }

}

run RocketMQProducerTest.java 之后，RocketMQProducerTest.java 对应的控制台输出为：

1. messageId=0A71290100002A9F00000003D0BB0832, status=SEND_OK
2. messageId=0A71290100002A9F00000003D0BB08BB, status=SEND_OK
3. messageId=0A71290100002A9F00000003D0BB0944, status=SEND_OK
4. messageId=0A71290100002A9F00000003D0BB09CD, status=SEND_OK
5. messageId=0A71290300002A9F000000005440AEED, status=SEND_OK

结果分析：表明所有消息都已经正常发送，且被RocketMQ正常接收。

此时查看RocketMQConsumerTest.java对应的控制台输出发生改变，输出内容变更如下:

1. RocketMQConsumer Started! group=CONSUMER-MQ-GROUP instance=1eb7d308-4414-4658-90b5-e2cae3b793eb
2. msg data from rocketMQ:I send message to RocketMQ 1
3. msg data from rocketMQ:I send message to RocketMQ 0
4. msg data from rocketMQ:I send message to RocketMQ 3
5. msg data from rocketMQ:I send message to RocketMQ 2
6. msg data from rocketMQ:I send message to RocketMQ 4

看，简单吧！

备注：小编自己使用了Apache版本的RocketMQ(即RocketMQ 4.*)，发现只需要更改import的package的路径而已，不需要修改其他代码，请参考。

RocketMQ的重复问题解决方式：

a.MQ的消费端执行的操作具有幂等性，即无论多少次重复执行，其结果是一样的；

b.MQ的消费端做重复校验，比如将受到MQ消息的唯一编号保存到Redis中，即每次收到消息时，将检查唯一编号是否已经在Redis中，如果存在说明消息重复；否则将唯一编号放入到Redis中，可以根据系统需要设置唯一编号在Redis中的过期时间，以防止Redis溢出。