前言：上一篇文章，我们已经搭建好MQTT服务器了，并且DTU设备。链接好传感器也能直接往MQTT消息发送收集的HEX格式的温湿度数据了。所以下一步我们需要写个程序把这个消息给接收到，然后对消息进行处理、本人使用的是java程序，对MQTT的消息进行处理

介绍：搭建使用的是若依基本的脚手架，前后端分离的版本，可自行搜索下载，这里就不在多做介绍

1、添加mqtt依赖

        <!--mqtt-->
        <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>

        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.9</version>
        </dependency>

2、配置一下yml配置文件信息

spring:
    mqtt:
        username: MQTT2 # 用户名
        password: 123456 # 密码
        hostUrl: tcp://mqtt服务器ip:1883 # tcp://服务器ip:1883
        clientId: client_java # 客户端名称(名称不能命名一样的)
        defaultTopic: dtutopic # 订阅主题
        timeout: 100 # 超时时间 （单位：秒）
        keepalive: 60 # 心跳 （单位：秒）
        enabled: true # 是否使能mqtt功能
        millis: 300 # 间隔多长时间发布一组数据 (毫秒)

3、MqttConfing类配置信息

package com.ruoyi.framework.config;

import com.ruoyi.framework.web.mqtt.MqttPushClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties("spring.mqtt")
public class MqttConfig {
    @Autowired
    private MqttPushClient mqttPushClient;

    /**
     * 用户名
     */
    private String username;
    /**
     * 密码
     */
    private String password;
    /**
     * 连接地址
     */
    private String hostUrl;
    /**
     * 客户Id
     */
    private String clientId;
    /**
     * 默认连接话题
     */
    private String defaultTopic;
    /**
     * 超时时间
     */
    private int timeout;
    /**
     * 保持连接数
     */
    private int keepalive;
    /**
     * mqtt功能使能
     */
    @Value("${spring.mqtt.enabled}")
    private boolean enabled;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getHostUrl() {
        return hostUrl;
    }

    public void setHostUrl(String hostUrl) {
        this.hostUrl = hostUrl;
    }

    public String getClientId() {
        return clientId;
    }

    public void setClientId(String clientId) {
        this.clientId = clientId;
    }

    public String getDefaultTopic() {
        return defaultTopic;
    }

    public void setDefaultTopic(String defaultTopic) {
        this.defaultTopic = defaultTopic;
    }

    public int getTimeout() {
        return timeout;
    }

    public void setTimeout(int timeout) {
        this.timeout = timeout;
    }

    public int getKeepalive() {
        return keepalive;
    }

    public void setKeepalive(int keepalive) {
        this.keepalive = keepalive;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }


    @Bean
    public MqttPushClient getMqttPushClient() {

        if(enabled == true){
            //单个主题订阅
            mqttPushClient.connect(hostUrl, clientId, username, password, timeout, keepalive);//连接
            mqttPushClient.subscribe(defaultTopic, 0);//订阅主题

        }
        return mqttPushClient;
    }
}

注意：我这里订阅了单个主题，所以这个这么写的，如果订阅多个主题要对应修改

if(enabled == true){
            String mqtt_topic[] = StringUtils.split(defaultTopic, ",");
            mqttPushClient.connect(hostUrl, clientId, username, password, timeout, keepalive);//连接
            for(int i=0; i<mqtt_topic.length; i++){
                mqttPushClient.subscribe(mqtt_topic[i], 0);//订阅主题
            }
        }

4、订阅MQTT消息的类MqttPushClient 和MqttMsgCallback

package com.ruoyi.framework.web.mqtt;

import com.ruoyi.framework.web.domain.AjaxResult;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * Mqtt推送客户端
 */

@Component
public class MqttPushClient {
    private static final Logger logger = LoggerFactory.getLogger(MqttPushClient.class);

    @Autowired
    private MqttMsgCallback mqttMsgCallback;

    private static MqttClient client;

    private static MqttClient getClient() {
        return client;
    }

    private static void setClient(MqttClient client) {
        MqttPushClient.client = client;
    }

    /**
     * 客户端连接
     *
     * @param host      ip+端口
     * @param clientID  客户端Id
     * @param username  用户名
     * @param password  密码
     * @param timeout   超时时间
     * @param keepalive 保留数
     */
    public void connect(String host, String clientID, String username, String password, int timeout, int keepalive) {
        MqttClient client;
        try {
            client = new MqttClient(host, clientID, new MemoryPersistence());
            MqttConnectOptions options = new MqttConnectOptions();
            options.setCleanSession(true);
            options.setUserName(username);
            options.setPassword(password.toCharArray());
            options.setConnectionTimeout(timeout);
            options.setKeepAliveInterval(keepalive);
            MqttPushClient.setClient(client);
            try {
                client.setCallback(mqttMsgCallback);
                client.connect(options);
            } catch (Exception e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 发布
     *
     * @param qos         连接方式
     * @param retained    是否保留
     * @param topic       主题
     * @param pushMessage 消息体
     */
    public AjaxResult publish(int qos, boolean retained, String topic, String pushMessage) {

        MqttMessage message = new MqttMessage();
        message.setQos(qos);
        message.setRetained(retained);
        message.setPayload(pushMessage.getBytes());

        MqttTopic mTopic = MqttPushClient.getClient().getTopic(topic);
        if (null == mTopic) {
            logger.error("topic not exist");
        }
        MqttDeliveryToken token;
        try {
            token = mTopic.publish(message);
            token.waitForCompletion();
            return AjaxResult.success();
        } catch (MqttPersistenceException e) {
            e.printStackTrace();
            return AjaxResult.error();
        } catch (MqttException e) {
            e.printStackTrace();
            return AjaxResult.error();
        }
    }

    /**
     * 订阅某个主题
     *
     * @param topic 主题
     * @param qos   连接方式
     */
    public void subscribe(String topic, int qos) {
        logger.info("开始订阅主题：" + topic);
        try {
            MqttPushClient.getClient().subscribe(topic, qos);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

}

MqttMsgCallback

package com.ruoyi.framework.web.mqtt;

import com.ruoyi.framework.config.MqttConfig;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * Mqtt订阅端
 */

@Component
public class MqttMsgCallback implements MqttCallback {

    private static final Logger logger = LoggerFactory.getLogger(MqttPushClient.class);

    @Autowired
    private MqttConfig mqttConfig;

    private static MqttClient client;

    @Override
    public void connectionLost(Throwable throwable) {
        logger.info("连接断开，进行重连");// 连接丢失后，一般在这里面进行重连
        if (client == null || !client.isConnected()) {
            mqttConfig.getMqttPushClient();
        }
    }

    @Override
    public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
        // 订阅后得到的消息会执行到这里面
        logger.info("接收消息主题 : " + topic);
        logger.info("接收消息Qos : " + mqttMessage.getQos());

        byte[] payload = mqttMessage.getPayload();
        // 打印读取的数据
        String data3 = bytesToHex(payload).trim();
        //去除空格
        String[] hexBytes = data3.split(" ");
        byte[] bytes = new byte[hexBytes.length];
        for (int i = 0; i < hexBytes.length; i++) {
            bytes[i] = (byte) Integer.parseInt(hexBytes[i], 16);
        }
        // 偏置地址为1的温度数据
        float temperature = bytes[3] << 8 | (bytes[4] & 0xFF); // bytes[3]是高字节，bytes[4]是低字节
        // 偏置地址为2的湿度数据
        float humidity = bytes[5] << 8 | (bytes[6] & 0xFF); // bytes[5]是高字节，bytes[6]是低字节

        // 输出结果
        logger.info("温度数据: " + temperature/10+"℃");
        logger.info("湿度数据: " + humidity/10+"%");
        

    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {

        logger.info("deliveryComplete---------" + iMqttDeliveryToken.isComplete());
    }

    // 将字节数组转换成十六进制字符串，方便查看
    private static String bytesToHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
            sb.append(String.format("%02X ", b));
        }
        return sb.toString();
    }

}

之后就配置结束啦，然后开始启动若依项目，项目启动的时候，就回去订阅我们指定的topic了。

5、打开,MQTTX客户端工具，对设备进行订阅监听，过几分钟后，我们的客户端工具已经成功的收到设备发到MQTT的数据了

6、看一下MQTT主页（见上一篇博客），有几个客户端连接，通过每个客户端的链接ID（之前强调的是每个客户端连接ID不能相同），可以看到，目前三个客户端都正常链接着在。DTU设备，向主题发消息，java程序和MQTTX订阅消费这个主题消息，具体的clientId，可以看下我之前的博客，都是对应的上的

这是再看下控制台已经打印出来的了，和客户端工具相同的数据，因为客户端工具，和我们的程序是同时订阅MQTTd的dtutopic主题的，所以能收到相同的数据,说明我们的消息是通了。

之后的步骤，就自己对这些数据进行处理了，是入库还是做其他操作，都在MqttMsgCallback类中进行处理

 上篇文章：windows搭建mqtt服务器，并配置DTU收集传感器数据（上）

文章参考：springboot整合mqtt-CSDN博客