MQTT随笔

原创已于 2024-03-19 13:41:44 修改 · 1.4k 阅读

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#java

于 2024-03-14 13:51:34 首次发布

本文介绍了如何在SpringIntegration中使用MQTT协议进行通信，包括Maven依赖配置、连接参数设置、发布/订阅操作以及回调函数的实现。还展示了如何在项目启动时自动订阅特定主题。

一、MQTT 是基于发布(Publish)/订阅(Subscribe) 模式来进行通信及数据交换的。

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二、使用

1.maven依赖

<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-mqtt</artifactId>
    <version>6.0.6</version>
</dependency>

2.配置类

public class MQTTConfig {

    //连接地址
    private static String url;
    //账号
    private static String username;
    //密码
    private static String password;
    //回调地址
    private static String back = "";

}

3. 连接工具

public class MQTTConnect {
    
    //连接服务器默认客户端ID
    private final String clientId = "AS" + DateUtils.dateMonth();

    private MqttClient mqttClient;

    //@Autowired
    //private RedisCache redisCache;

    public void setMqttClient(String userName, String passWord, MqttCallback mqttCallback) throws MqttException {
        MqttConnectOptions options = mqttConnectOptions(userName, passWord);
        if (mqttCallback == null) {
            mqttClient.setCallback(new Callback());
        } else {
            mqttClient.setCallback(mqttCallback);
        }
        mqttClient.connect(options);
    }


    /**
     * MQTT连接参数设置
     */
    private MqttConnectOptions mqttConnectOptions(String userName, String passWord) throws MqttException {
        mqttClient = new MqttClient(MQTTConfig.getUrl(), clientId, new MemoryPersistence());
        MqttConnectOptions options = new MqttConnectOptions();
        options.setUserName(userName);
        options.setPassword(passWord.toCharArray());
        options.setConnectionTimeout(10);
        options.setCleanSession(false);
        return options;
    }

    /**
     * 关闭MQTT连接
     */
    public void close() throws MqttException {
        mqttClient.disconnect();
        mqttClient.close();
    }

    /**
     * 向某个主题发布消息 默认qos：1
     *
     * @param topic:发布的主题
     * @param msg：发布的消息
     */
    public void pub(String topic, String msg) throws MqttException {
        MqttMessage mqttMessage = new MqttMessage();
        mqttMessage.setPayload(msg.getBytes());
        MqttTopic mqttTopic = mqttClient.getTopic(topic);
        MqttDeliveryToken token = mqttTopic.publish(mqttMessage);
        token.waitForCompletion();
    }

    /**
     * 向某个主题发布消息
     *
     * @param topic: 发布的主题
     * @param msg:   发布的消息
     * @param qos:   消息质量    Qos：0、1、2
     */
    public void pub(String topic, String msg, int qos) throws MqttException {
        MqttMessage mqttMessage = new MqttMessage();
        mqttMessage.setQos(qos);
        mqttMessage.setPayload(msg.getBytes());
        MqttTopic mqttTopic = mqttClient.getTopic(topic);
        MqttDeliveryToken token = mqttTopic.publish(mqttMessage);
        token.waitForCompletion();
    }

    /**
     * 订阅某一个主题 ，此方法默认的的Qos等级为：1
     *
     * @param topic 主题
     */
    public void sub(String topic) throws MqttException {
        mqttClient.subscribe(topic);
    }

    public void sub(String[] topic) throws MqttException {
        mqttClient.subscribe(topic);
    }

    /**
     * 订阅某一个主题，可携带Qos
     *
     * @param topic 所要订阅的主题
     * @param qos   消息质量：0、1、2
     */
    public void sub(String topic, int qos) throws MqttException {
        mqttClient.subscribe(topic, qos);
    }

}

4. 发布/订阅回调返回

@Component
public class Callback implements MqttCallback {

/**
  * MQTT 断开连接会执行此方法
  */
 @Override
 public void connectionLost(Throwable throwable) {
    log.info("断开了MQTT连接 ：{}", throwable.getMessage());
    log.error(throwable.getMessage(), throwable);
 }

 /**
  * publish发布成功后会执行到这里
  */
 @Override
 public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
 }

 /**
  * subscribe订阅后得到的消息会执行到这里
  */
 @Override
 public void messageArrived(String topic, MqttMessage message) {
    log.info("收到来自 " + topic + " 的消息：{}", newString(message.getPayload()));
 }

}

5.项目启动自动订阅

@Component
public class MQTTBack implements CommandLineRunner {

    private final String clientId = DateUtils.getYear();

    private final Logger log = LoggerFactory.getLogger(MQTTBack.class);

    @Override
    public void run(String... args) throws Exception {
        try {
            MemoryPersistence memoryPersistence = new MemoryPersistence();
            MqttConnectOptions options = new MqttConnectOptions();
            //设置用户名密码
            options.setUserName(MQTTConfig.getUsername());
            options.setPassword(MQTTConfig.getPassword().toCharArray());
            options.setCleanSession(true);
            //连接超时时间
            options.setConnectionTimeout(10);
            //设置会话心跳时间
            options.setKeepAliveInterval(30);
            MqttClient client = new MqttClient(MQTTConfig.getUrl(), clientId, memoryPersistence);
            client.setCallback(new Callback());
            client.connect(options);
            client.subscribe(MQTTConfig.getBack());
        } catch (Exception e) {
            log.info("上报数据启动出错：{}", e.getMessage());
        }
    }
  
    //重新连接
    public void reconnect() throws MqttException {
        MqttClient client = new MqttClient(MQTTConfig.getUrl(), clientId, new MemoryPersistence());
        client.connect();
        if (client.isConnected()) {
            System.out.println("Connected to MQTT server");
        } else {
            System.out.println("Not connected to MQTT server");
        }
    }
}