java连接MQTT服务器

一、业务场景

硬件采集的数据传入EMQX平台(采用MQTT协议)，java通过代码连接MQTT服务器，进行采集数据接收、解析、业务处理、存储入库、数据展示。

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

二、本文只讲解java连接MQTT服务器进行数据处理

1、新建springboot项目，pom文件中直接引入下面的mqtt依赖

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

2、编写MQTT工具类

package com.siborui.dc.mqtt;

import lombok.extern.slf4j.Slf4j;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 * MQTT工具类操作
 *
 * @author Mr.Qu
 * @since v1.1.0 2020-01-10
 */
@Slf4j
@Component
public class MQTTConnect {

    private String HOST = tcp://127.0.0.1:1883; //mqtt服务器的地址和端口号
    private final String clientId = "DC" + (int) (Math.random() * 100000000);
    private MqttClient mqttClient;

    /**
     * 客户端connect连接mqtt服务器
     *
     * @param userName     用户名
     * @param passWord     密码
     * @param mqttCallback 回调函数
     **/
    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(HOST, clientId, new MemoryPersistence());
        MqttConnectOptions options = new MqttConnectOptions();
        options.setUserName(userName);
        options.setPassword(passWord.toCharArray());
        options.setConnectionTimeout(10);///默认：30
        options.setAutomaticReconnect(true);//默认：false
        options.setCleanSession(false);//默认：true
        //options.setKeepAliveInterval(20);//默认：60
        return options;
    }

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

    /**
     * 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.setQos(2);
        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);
    }

    /**
     * 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);
    }

    /**
     * main函数自己测试用
     */
    public static void main(String[] args) throws MqttException {
        MQTTConnect mqttConnect = new MQTTConnect();
        mqttConnect.setMqttClient("admin", "public", new Callback());
        mqttConnect.pub("com/dc/init", "Mr.Qu" + (int) (Math.random() * 100000000));
        mqttConnect.sub("com/iot/init");
    }
}

3、编写MQTT的回调函数

package com.siborui.dc.mqtt;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;

/**
 * MQTT回调函数
 *
 * @author Mr.Qu
 * @since 2020/1/9 16:26
 */
public class Callback implements MqttCallback {

    /**
     * MQTT 断开连接会执行此方法
     */
    @Override
    public void connectionLost(Throwable throwable) {

    }

    /**
     * subscribe订阅后得到的消息会执行到这里
     */
    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {

    }
    
    /**
     * publish发布成功后会执行到这里
     */
    @Override
    public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
        //  TODO    此处可以将订阅得到的消息进行业务处理、数据存储
    }
}

4、由于业务场景需要，在项目启动时，监听MQTT主题Topic，编写MQTT监听器

package com.siborui.dc.mqtt;

import lombok.extern.slf4j.Slf4j;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

import com.siborui.dc.mqtt.Callback;

/**
 * 项目启动 监听主题
 *
 * @author Mr.Qu
 * @since 2020/1/10
 */
@Slf4j
@Component
public class MQTTListener implements ApplicationListener<ContextRefreshedEvent> {

    private final MQTTConnect server;

    @Autowired
    public MQTTListener(MQTTConnect server) {
        this.server = server;
    }

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        try {
            server.setMqttClient("admin", "public", new Callback());
            server.sub("com/iot/collection/");
        } catch (MqttException e) {
            log.error(e.getMessage(), e);
        }
    }
}

5、不明白之处请留言，感觉有用的给个打赏

来源：CSDN

作者：Iot-Mr.Qu

链接：https://blog.csdn.net/qq_37949192/article/details/103962848

标签

mqtt

topic

string

qos