java mqtt重连后订阅 mqtt断开重连

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编程梦想实现家 2023-12-28 16:14:10

文章标签 java mqtt重连后订阅 spring mqtt activemq eclipse 文章分类 Java 后端开发

一.pom.xml中添加mqtt的依赖：

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-integration</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-stream</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-mqtt</artifactId>
        </dependency>

二.application.properties配置文件中添加配置（其中MQTT的服务端使用的是ActiveMQ）：

## MQTT##
mqtt.host=tcp://127.0.0.1:1883
mqtt.clientId=mqttClient
mqtt.username=admin
mqtt.password=admin
mqtt.topicName1=topic1
mqtt.topicName2=topic2
mqtt.timeout=1000
mqtt.keepalive=2000

三.编码自己的MQTT客户端：

package mqtt2;

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * description:
 * author: yangzihe
 * date: 2018-12-17 17:33
 **/
public class MyMQTTClient {

    private static final Logger LOGGER = LoggerFactory.getLogger(MyMQTTClient.class);

    private static MqttClient client;

    public static MqttClient getClient() {
        return client;
    }

    public static void setClient(MqttClient client) {
        MyMQTTClient.client = client;
    }

    private String host;
    private String username;
    private String password;
    private String clientId;
    private int timeout;
    private int keepalive;

    public MyMQTTClient(String host, String username, String password, String clientId, int timeOut, int keepAlive) {
        this.host = host;
        this.username = username;
        this.password = password;
        this.clientId = clientId;
        this.timeout = timeOut;
        this.keepalive = keepAlive;
    }

    /**
     * 设置mqtt连接参数
     *
     * @param username
     * @param password
     * @param timeout
     * @param keepalive
     * @return
     */
    public MqttConnectOptions setMqttConnectOptions(String username, String password, int timeout, int keepalive) {
        MqttConnectOptions options = new MqttConnectOptions();
        options.setUserName(username);
        options.setPassword(password.toCharArray());
        options.setConnectionTimeout(timeout);
        options.setKeepAliveInterval(keepalive);
        options.setCleanSession(false);
        return options;
    }

    /**
     * 连接mqtt服务端，得到MqttClient连接对象
     */
    public void connect() throws MqttException {
        if (client == null) {
            client = new MqttClient(host, clientId, new MemoryPersistence());
            client.setCallback(new MyMQTTCallback(MyMQTTClient.this));
        }
        MqttConnectOptions mqttConnectOptions = setMqttConnectOptions(username, password, timeout, keepalive);
        if (!client.isConnected()) {
            client.connect(mqttConnectOptions);
        } else {
            client.disconnect();
            client.connect(mqttConnectOptions);
        }
        LOGGER.info("MQTT connect success");//未发生异常，则连接成功
    }

    /**
     * 发布，默认qos为0，非持久化
     *
     * @param pushMessage
     * @param topic
     */
    public void publish(String pushMessage, String topic) {
        publish(pushMessage, topic, 0, false);
    }

    /**
     * 发布消息
     *
     * @param pushMessage
     * @param topic
     * @param qos
     * @param retained:留存
     */
    public void publish(String pushMessage, String topic, int qos, boolean retained) {
        MqttMessage message = new MqttMessage();
        message.setPayload(pushMessage.getBytes());
        message.setQos(qos);
        message.setRetained(retained);
        MqttTopic mqttTopic = MyMQTTClient.getClient().getTopic(topic);
        if (null == mqttTopic) {
            LOGGER.error("topic is not exist");
        }
        MqttDeliveryToken token;//Delivery:配送
        synchronized (this) {//注意：这里一定要同步，否则，在多线程publish的情况下，线程会发生死锁，分析见文章最后补充
        try {
            token = mqttTopic.publish(message);//也是发送到执行队列中，等待执行线程执行，将消息发送到消息中间件
            token.waitForCompletion(1000L);
        } catch (MqttPersistenceException e) {
            e.printStackTrace();
        } catch (MqttException e) {
            e.printStackTrace();
        }
        }
    }

    /**
     * 订阅某个主题，qos默认为0
     *
     * @param topic
     */
    public void subscribe(String topic) {
        subscribe(topic, 0);
    }

    /**
     * 订阅某个主题
     *
     * @param topic
     * @param qos
     */
    public void subscribe(String topic, int qos) {
        try {
            MyMQTTClient.getClient().subscribe(topic, qos);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}

四.编码自己的MQTT回调对象：

package mqtt2;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * description:
 * author: yangzihe
 * date: 2018-12-17 17:37
 **/
public class MyMQTTCallback implements MqttCallback {

    private static final Logger LOGGER = LoggerFactory.getLogger(MyMQTTCallback.class);

    private MyMQTTClient myMQTTClient;

    public MyMQTTCallback(MyMQTTClient myMQTTClient) {
        this.myMQTTClient = myMQTTClient;
    }

    /**
     * 丢失连接，可在这里做重连
     * 只会调用一次
     *
     * @param throwable
     */
    @Override
    public void connectionLost(Throwable throwable) {
        LOGGER.error("连接断开，下面做重连...");
        long reconnectTimes = 1;
        while (true) {
            try {
                if (MyMQTTClient.getClient().isConnected()) {
                    LOGGER.warn("mqtt reconnect success end");
                    return;
                }
                LOGGER.warn("mqtt reconnect times = {} try again...", reconnectTimes++);
                MyMQTTClient.getClient().reconnect();
            } catch (MqttException e) {
                LOGGER.error("", e);
            }
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e1) {
                //e1.printStackTrace();
            }
        }
    }

    /**
     * 消息到达后
     * subscribe后，执行的回调函数
     *
     * @param s
     * @param mqttMessage
     * @throws Exception
     */
    @Override
    public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
        // subscribe后得到的消息会执行到这里面
        LOGGER.info("接收消息主题 : {}，接收消息内容 : {}", s, new String(mqttMessage.getPayload()));
    }

    /**
     * publish后，配送完成后回调的方法
     *
     * @param iMqttDeliveryToken
     */
    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
//        LOGGER.info("==========deliveryComplete={}==========", iMqttDeliveryToken.isComplete());
    }
}

五.编码MQTT配置类，将自己的MQTTClient客户端对象注入到spring容器中：

package mqtt2;

import lombok.extern.slf4j.Slf4j;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * description:
 * author: yangzihe
 * date: 2018-12-17 17:36
 **/
@Configuration
@Slf4j
public class MqttConfiguration {

    @Value("${mqtt.host}")
    String host;
    @Value("${mqtt.username}")
    String username;
    @Value("${mqtt.password}")
    String password;
    @Value("${mqtt.clientId}")
    String clientId;
    @Value("${mqtt.timeout}")
    int timeOut;
    @Value("${mqtt.keepalive}")
    int keepAlive;

    @Bean//注入spring
    public MyMQTTClient myMQTTClient() {
        MyMQTTClient myMQTTClient = new MyMQTTClient(host, clientId, username, password, timeOut, keepAlive);
        for (int i = 0; i < 10; i++) {
            try {
                myMQTTClient.connect();
                return myMQTTClient;
            } catch (MqttException e) {
                log.error("MQTT connect exception,connect time = " + i);
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
                //e.printStackTrace();
            }
        }
        return myMQTTClient;
    }

}

六.编写测试类，测试发布以及订阅：

package demo;

import mqtt2.MyMQTTClient;
import mqtt2.SpringBootApplicationMQTT2;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;

/**
 * description:
 * author: yangzihe
 * date: 2018-12-17 17:37
 **/
@SpringBootTest(classes = SpringBootApplicationMQTT2.class)
@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
public class MQTTTest2 {

    @Autowired
    private MyMQTTClient myMQTTClient;

    @Test
    public void testProduce() throws Exception {
        long l = System.nanoTime();
        for (int i = 0; i < 20000; i++) {
            String topicName = "topic11";
            //myMQTTClient.subscribe(topicName);
            myMQTTClient.publish(topicName + "发送消息" + i, topicName);
        }
        long l1 = System.nanoTime();
        double d = ((double) (l1 - l)) / 1000000000;
        long l2 = System.nanoTime();
        for (int i = 0; i < 20000; i++) {
            String topicName = "topic22";
            //myMQTTClient.subscribe(topicName);
            myMQTTClient.publish(topicName + "发送消息" + i, topicName);
        }
        double d2 = ((double) (System.nanoTime() - l2)) / 1000000000;
        System.err.println("=====================第一个topic发送2万数据花费时间：=================" + d + "秒");//2秒多
        System.err.println("=====================第二个topic发送2万数据花费时间：=================" + d2 + "秒");
    }

    /**
     * 分级发布与订阅
     * @throws Exception
     */
    @Test
    public void testTopic() throws Exception {
        int count = 10;
        String topicName1 = "topic33/type/name";
        String topicName2 = "topic33/type";
        String topicName3 = "topic33";
        myMQTTClient.subscribe(topicName3+"/#");
        for (int i = 0; i < count; i++) {
            myMQTTClient.publish(topicName1 + "发送消息" + i, topicName1);
        }
        for (int i = 0; i < count; i++) {
            myMQTTClient.publish(topicName2 + "发送消息" + i, topicName2);
        }
        for (int i = 0; i < count; i++) {
            myMQTTClient.publish(topicName3 + "发送消息" + i, topicName3);
        }
    }

}

其中SpringBootApplicationMQTT2是springboot的启动类：

package mqtt2;

import org.springframework.boot.SpringApplication;

/**
 * ClassName: SpringBootApplication
 * description:
 * author: yangzihe
 * date: 2018-09-30 09:15
 **/
@org.springframework.boot.autoconfigure.SpringBootApplication//@EnableAutoConfiguration @ComponentScan
public class SpringBootApplicationMQTT2 {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootApplicationMQTT2.class, args);
    }


}

运行结果：

java mqtt重连后订阅 mqtt断开重连_activemq

补充：为什么publish时一定要同步？

synchronized (this) {
                try {
                    token = mqttTopic.publish(message);
                    token.waitForCompletion(1000L);
                } catch (MqttPersistenceException e) {
                    e.printStackTrace();
                } catch (MqttException e) {
                    e.printStackTrace();
                }
            }

查看mqttTopic.publish(message)源码：

public MqttDeliveryToken publish(MqttMessage message) throws MqttException, MqttPersistenceException {
        MqttDeliveryToken token = new MqttDeliveryToken(this.comms.getClient().getClientId());
        token.setMessage(message);
        this.comms.sendNoWait(this.createPublish(message), token);
        token.internalTok.waitUntilSent();
        return token;
    }

每次publish都是new MqttDeliveryToken，然后查看token.internalTok.waitUntilSent()源码：

public void waitUntilSent() throws MqttException {
        Object var1 = this.sentLock;
        synchronized(this.sentLock) {
            Object var2 = this.responseLock;
            synchronized(this.responseLock) {
                if (this.exception != null) {
                    throw this.exception;
                }
            }

            while(!this.sent) {
                try {
                    log.fine(CLASS_NAME, "waitUntilSent", "409", new Object[]{this.getKey()});
                    //消息未发送到队列中，sentLock就wait，线程进入等待，同时释放了锁sentLock
                    this.sentLock.wait();
                } catch (InterruptedException var3) {
                    ;
                }
            }

            if (!this.sent) {
                if (this.exception == null) {
                    throw ExceptionHelper.createMqttException(6);
                } else {
                    throw this.exception;
                }
            }
        }
    }

this.sentLock.wait()在当前线程还未将消息发送到队列中去时，当前线程进入等待状态，在有其他线程唤醒时，代码继续往下执行。一直到消息发送到队列中标识sent为true时，线程结束循环，结束函数。若没有其他线程唤醒或者消息发送标识sent=false，线程则一直等待下去。

因为是new MqttDeliveryToken，Token也是new的，所以sent不会受多线程影响（每条消息有着自己的sent）。

所以猜测是没有线程唤醒本线程，那么什么时候才会有线程唤醒本线程？

猜测： this.comms.sendNoWait(this.createPublish(message), token); 中有taskExecutor去执行“将消息发送到队列中”task，task执行完成后，会将sent=true，然后notifyAll()。然而，在多线程的时候，this.comms.sendNoWait(this.createPublish(message), token)的this是同一个MqttTopic时（topic名相同时），线程1等待时被线程2抢到cpu执行权，线程2会将taskExecutor执行的task更新为线程2的task，线程1再执行时没有了task，不会notifyAll()，就会一直等待下去了。

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