maven的pom.xml引入包

        <!--mqtt-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-integration</artifactId>
            <version>2.3.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-stream</artifactId>
            <version>5.3.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-mqtt</artifactId>
            <version>5.3.4.RELEASE</version>
        </dependency>

mqtt.yml配置文件

spring:
  mqtt:
    username: admin
    password: beyond_2021
    url: tcp://192.168.3.100:1883
    client-id: data-clientId
    server-id: data-serverId
    data-topic: data/#
    will-topic: data-will
    will-content: data server offline
    completion-timeout: 10000

初始化MQTT配置bean

package com.beyond.config;

import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.EventListener;
import org.springframework.integration.annotation.IntegrationComponentScan;
import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.core.MessageProducer;
import org.springframework.integration.mqtt.core.DefaultMqttPahoClientFactory;
import org.springframework.integration.mqtt.core.MqttPahoClientFactory;
import org.springframework.integration.mqtt.event.MqttConnectionFailedEvent;
import org.springframework.integration.mqtt.event.MqttMessageDeliveredEvent;
import org.springframework.integration.mqtt.event.MqttMessageSentEvent;
import org.springframework.integration.mqtt.event.MqttSubscribedEvent;
import org.springframework.integration.mqtt.inbound.MqttPahoMessageDrivenChannelAdapter;
import org.springframework.integration.mqtt.outbound.MqttPahoMessageHandler;
import org.springframework.integration.mqtt.support.DefaultPahoMessageConverter;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.MessagingException;

import java.security.SecureRandom;
import java.util.Date;


@Configuration
@IntegrationComponentScan
public class MqttConfig {

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

    @Value("${spring.mqtt.username}")
    private String username;

    @Value("${spring.mqtt.password}")
    private String password;

    @Value("${spring.mqtt.url}")
    private String hostUrl;

    @Value("${spring.mqtt.client-id}")
    private String clientId;

    @Value("${spring.mqtt.server-id}")
    private String serverId;

    @Value("${spring.mqtt.data-topic:data/#}")
    private String dataTopic;

    @Value("${spring.mqtt.will-topic}")
    private String willTopic;

    @Value("${spring.mqtt.will-content}")
    private String willContent;

    /**
     * @desc 连接超时
     */
    @Value("${spring.mqtt.completion-timeout}")
    private int completionTimeout ;

    @Bean
    public MqttConnectOptions getMqttConnectOptions(){
        // MQTT的连接设置
        MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();
        // 设置连接的用户名
        mqttConnectOptions.setUserName(username);
        // 设置连接的密码
        mqttConnectOptions.setPassword(password.toCharArray());
        // 设置是否清空session,这里如果设置为false表示服务器会保留客户端的连接记录，
        // 把配置里的 cleanSession 设为false，客户端掉线后 服务器端不会清除session，
        // 当重连后可以接收之前订阅主题的消息。当客户端上线后会接受到它离线的这段时间的消息
        mqttConnectOptions.setCleanSession(true);
        // 设置发布端地址,多个用逗号分隔, 如:tcp://111:1883,tcp://222:1883
        // 当第一个111连接上后,222不会在连,如果111挂掉后,重试连111几次失败后,会自动去连接222
        mqttConnectOptions.setServerURIs(hostUrl.split(","));
        // 设置会话心跳时间 单位为秒 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制
        mqttConnectOptions.setKeepAliveInterval(20);
        mqttConnectOptions.setAutomaticReconnect(true);
        // 设置“遗嘱”消息的话题，若客户端与服务器之间的连接意外中断，服务器将发布客户端的“遗嘱”消息。
        mqttConnectOptions.setWill(willTopic, willContent.getBytes(), 2, false);
        mqttConnectOptions.setMaxInflight(1000000);
        return mqttConnectOptions;
    }

    @Bean
    public MqttPahoClientFactory mqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        factory.setConnectionOptions(getMqttConnectOptions());
        return factory;
    }

    /**
     * @desc 发送通道配置 默认主题
     * @date 2021/3/16
     */
    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel")
    public MessageHandler mqttOutbound() {
        //clientId每个连接必须唯一,否则,两个相同的clientId相互挤掉线
        String clientIdStr = clientId + new SecureRandom().nextInt(10);
        MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler(clientIdStr, mqttClientFactory());
        //async如果为true，则调用方不会阻塞。而是在发送消息时等待传递确认。默认值为false（发送将阻塞，直到确认发送)
        messageHandler.setAsync(true);
        messageHandler.setAsyncEvents(true);
        messageHandler.setDefaultTopic(dataTopic);
        messageHandler.setDefaultQos(1);
        return messageHandler;
    }

    /**
     * @desc 发送通道
     * @date 2021/3/16
     */
    @Bean
    public MessageChannel mqttOutboundChannel() {
        return new DirectChannel();
    }

    /**
     * @desc 接收通道
     * @date 2021/3/16
     */
    @Bean
    public MessageChannel mqttInputChannel() {
        return new DirectChannel();
    }

    /**
     * @desc 配置监听的 topic 支持通配符
     * @date 2021/3/16
     */
    @Bean
    public MessageProducer inbound() {
        //clientId每个连接必须唯一,否则,两个相同的clientId相互挤掉线
        String serverIdStr = serverId + new SecureRandom().nextInt(10);
        MqttPahoMessageDrivenChannelAdapter adapter =
                new MqttPahoMessageDrivenChannelAdapter(serverIdStr, mqttClientFactory(), dataTopic);
        adapter.setCompletionTimeout(completionTimeout);
        adapter.setConverter(new DefaultPahoMessageConverter());
        adapter.setQos(1);
        adapter.setOutputChannel(mqttInputChannel());
        return adapter;
    }

    /**
     * @desc 通过通道获取数据 订阅的数据
     * @date 2021/3/16
     */
    @Bean
    @ServiceActivator(inputChannel = "mqttInputChannel")
    public MessageHandler handler() {
        return new MessageHandler() {
            @Override
            public void handleMessage(Message<?> message) throws MessagingException {
                String payload = message.getPayload().toString();
                String topic = message.getHeaders().get(MqttHeaders.RECEIVED_TOPIC).toString();
                //////////////////处理订阅topic:(data/#)到的所有的数据
            }
        };
    }

    /**
     * @desc mqtt连接失败或者订阅失败时,触发MqttConnectionFailedEvent事件
     * @date 2021/7/22
      *@param event
     * @return void
     */
    @EventListener(MqttConnectionFailedEvent.class)
    public void mqttConnectionFailedEvent(MqttConnectionFailedEvent event) {
        log.error("mqttConnectionFailedEvent连接mqtt失败: " +
                "date={}, hostUrl={}, username={}, error={}",
                new Date(), hostUrl, username, event.getCause().getMessage());
    }

    /**
     * @desc 当async和async事件(async-events)都为true时,将发出MqttMessageSentEvent
     * 它包含消息、主题、客户端库生成的消息id、clientId和clientInstance（每次连接客户端时递增）
     * @date 2021/7/22
      *@param event
     * @return void
     */
    @EventListener(MqttMessageSentEvent.class)
    public void mqttMessageSentEvent(MqttMessageSentEvent event) {
        log.info("mqttMessageSentEvent发送信息: date={}, info={}", new Date(), event.toString());
    }

    /**
     * @desc 当async和async事件(async-events)都为true时,将发出MqttMessageDeliveredEvent
     * 当客户端库确认传递时，将发出MqttMessageDeliveredEvent。它包含messageId、clientId和clientInstance，使传递与发送相关。
     * @date 2021/7/22
      *@param event
     * @return void
     */
    @EventListener(MqttMessageDeliveredEvent.class)
    public void mqttMessageDeliveredEvent(MqttMessageDeliveredEvent event) {
        log.info("mqttMessageDeliveredEvent发送成功信息: date={}, info={}", new Date(), event.toString());
    }

    /**
     * @desc 成功订阅到主题，MqttSubscribedEvent事件就会被触发(多个主题,多次触发)
     * @date 2021/7/22
      *@param event
     * @return void
     */
    @EventListener(MqttSubscribedEvent.class)
    public void mqttSubscribedEvent(MqttSubscribedEvent event) {
        log.info("mqttSubscribedEvent订阅成功信息: date={}, info={}", new Date(), event.toString());
    }

}

mqtt发送数据网关配置

package com.beyond.data.component;

import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.handler.annotation.Header;
import org.springframework.stereotype.Component;

/**
 * @desc MQTT发送网关
 * @date 2021/3/12
 */
@Component
@MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
public interface MqttGatewayComponent {

    void sendToMqtt(String data);

    void sendToMqtt(String payload, @Header(MqttHeaders.TOPIC) String topic);

    void sendToMqtt(@Header(MqttHeaders.TOPIC) String topic, @Header(MqttHeaders.QOS) int qos, String payload);

}

发送数据到mqtt伪代码

@Autowired
private MqttGatewayComponent mqttGatewayComponent;

//发送字符串或json字符串,到指定的topic
mqttGatewayComponent.sendToMqtt("json string", "data/abcd");

参考链接:
https://blog.csdn.net/sinat_21184471/article/details/87186186
https://blog.csdn.net/qq_29467891/article/details/107043225?utm_source=app
https://blog.csdn.net/myinsert/article/details/107715538