最近项目中用到Emqx发布/订阅数据，特此记录便于日后查阅。

        ThingsboardEmqxTransportApplication

/**
 * Copyright  2016-2023 The Thingsboard Authors
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.thingsboard.server.emqx;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.integration.config.EnableIntegration;

import java.util.Arrays;

@SpringBootConfiguration
@EnableConfigurationProperties
@EnableIntegration
@ComponentScan({"org.thingsboard.server.transport.emqx"})
public class ThingsboardEmqxTransportApplication {

    private static final String SPRING_CONFIG_NAME_KEY = "--spring.config.name";
    private static final String DEFAULT_SPRING_CONFIG_PARAM = SPRING_CONFIG_NAME_KEY + "=" + "tb-emqx-transport";

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

    private static String[] updateArguments(String[] args) {
        if (Arrays.stream(args).noneMatch(arg -> arg.startsWith(SPRING_CONFIG_NAME_KEY))) {
            String[] modifiedArgs = new String[args.length + 1];
            System.arraycopy(args, 0, modifiedArgs, 0, args.length);
            modifiedArgs[args.length] = DEFAULT_SPRING_CONFIG_PARAM;
            return modifiedArgs;
        }
        return args;
    }
}

        GMqttPahoMessageDrivenChannelAdapter

package org.thingsboard.server.transport.emqx.adpter;

import lombok.extern.slf4j.Slf4j;
import org.springframework.integration.mqtt.core.MqttPahoClientFactory;
import org.springframework.integration.mqtt.inbound.MqttPahoMessageDrivenChannelAdapter;

/**
 * @author zhangzhixiang on 2023/4/12
 */
@Slf4j
public class GMqttPahoMessageDrivenChannelAdapter extends MqttPahoMessageDrivenChannelAdapter {

    public GMqttPahoMessageDrivenChannelAdapter(String url, String clientId, MqttPahoClientFactory clientFactory,
                                                String... topic) {
        super(url, clientId, clientFactory, topic);
    }

    /**
     * Fix Bug.
     *
     * <p> 死锁描述：
     * Found one Java-level deadlock:
     * =============================
     * "MQTT Rec: iot-shadow-restapi_sub_hqxzgpcy":
     * waiting for ownable synchronizer 0x00000000d73e9d70, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
     * which is held by "main"
     * "main":
     * waiting to lock monitor 0x00007f5840008bf8 (object 0x00000000d73d2480, a org.springframework.integration
     * .mqtt.inbound.MqttPahoMessageDrivenChannelAdapter),
     * which is held by "MQTT Rec: iot-shadow-restapi_sub_hqxzgpcy"
     *
     * <p> 原因分析：
     * main主线程
     * AbstractEndpoint.start()获取到了ReentrantLock锁
     * MqttPahoMessageDrivenChannelAdapter.scheduleReconnect()但是需要MqttPahoMessageDrivenChannelAdapter对象锁
     * MQTT Rec线程
     * 获取到了MqttPahoMessageDrivenChannelAdapter对象锁，但是需要ReentrantLock锁
     *
     * @param cause
     */
    @Override
    public void connectionLost(Throwable cause) {
        try {
            this.lifecycleLock.lock();
        } catch (Exception e) {
            log.error("Stack Trace: {}", e);
        } finally {
            this.lifecycleLock.unlock();
        }
        super.connectionLost(cause);
    }
}

          MqttConfig

package org.thingsboard.server.transport.emqx.config;

import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.RandomStringUtils;
import org.apache.commons.lang3.StringUtils;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
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.inbound.MqttPahoMessageDrivenChannelAdapter;
import org.springframework.integration.mqtt.outbound.MqttPahoMessageHandler;
import org.springframework.integration.mqtt.support.DefaultPahoMessageConverter;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.MessagingException;
import org.thingsboard.server.transport.emqx.DefaultMqttSubMessageHandler;
import org.thingsboard.server.transport.emqx.MqttSubMessageHandler;
import org.thingsboard.server.transport.emqx.adpter.GMqttPahoMessageDrivenChannelAdapter;
import org.thingsboard.server.transport.emqx.constant.Qos;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.net.ssl.SSLSocketFactory;

/**
 * @author zhangzhixiang on 2023/4/12
 */
@Data
@Slf4j
@Configuration
@ConfigurationProperties(prefix = "emqx")
@IntegrationComponentScan
public class MqttConfig {

    private String url;
    private String username;
    private String password;
    private int timeout;
    private int keepalive;
    private String enabled;
    private String subClientId;
    private String pubClientId;
    private MqttSubMessageHandler messageHandler;
    private MqttPahoMessageDrivenChannelAdapter adapter;
    private boolean dataVerifyEnabled;
    private boolean sslVerifyEnabled;
    private String caCertFile;
    private String clientCertFile;
    private String clientKeyFile;
    private String[] defaultTopics;

    ///
    // mqtt subscribe
    ///
    @PostConstruct
    public void init() {
        inbound();
        addTopic(defaultTopics);
        setMessageHandler(new DefaultMqttSubMessageHandler());
        log.info("EMQX transport started!");
    }

    @PreDestroy
    public void shutdown() {
        log.info("Stopping EMQX transport!");
        removeTopic(defaultTopics);
        log.info("EMQX transport stopped!");
    }

    @Bean
    public MessageChannel mqttInputChannel() {
        return new DirectChannel();
    }

    @Bean
    public MessageProducer inbound() {
        this.subClientId = createMqttClientId(false);
        adapter = new GMqttPahoMessageDrivenChannelAdapter(url, subClientId, mqttClientFactory());
        adapter.setCompletionTimeout(5000);
        adapter.setConverter(new DefaultPahoMessageConverter());
        adapter.setQos(Qos.DEFAULT.getValue());
        adapter.setOutputChannel(mqttInputChannel());
        log.info("Success to initialize Mqtt channel adapter for subscribe, " +
                "url=[{}],subClientId=[{}],sslVerifyEnabled=[{}]", url, subClientId, sslVerifyEnabled);
        return adapter;
    }

    @Bean
    @ServiceActivator(inputChannel = "mqttInputChannel")
    public MessageHandler handler() {
        return new MessageHandler() {
            @Override
            public void handleMessage(Message<?> message) throws MessagingException {
                messageHandler.receiveMessage(message);
            }
        };
    }

    @Bean
    public MqttPahoClientFactory mqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        MqttConnectOptions options = new MqttConnectOptions();
        options.setCleanSession(true);
        options.setUserName(username);
        options.setPassword(password.toCharArray());
        options.setConnectionTimeout(timeout);
        options.setKeepAliveInterval(keepalive);
        // automaticReconnect 为 true 表示断线自动重连，但仅仅只是重新连接，并不订阅主题；在 connectComplete 回调函数重新订阅
        options.setAutomaticReconnect(true);
        options.setServerURIs(new String[]{url});
        if (sslVerifyEnabled) {
            try {
                SSLSocketFactory sslSocketFactory = SSLFellow.createSSLSocketFactory(
                        caCertFile, clientCertFile, clientKeyFile);
                options.setSocketFactory(sslSocketFactory);
            } catch (Exception e) {
                log.error("Stack Trace: {}", e);
            }
        }
        factory.setConnectionOptions(options);
        return factory;
    }

    ///
    // mqtt publish
    ///
    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel")
    public MessageHandler mqttOutbound() {
        this.pubClientId = createMqttClientId(true);
        MqttPahoMessageHandler messageHandler =
                new MqttPahoMessageHandler(pubClientId, mqttClientFactory());
        messageHandler.setAsync(true);
        messageHandler.setDefaultQos(Qos.DEFAULT.getValue());
        log.info("Success to initialize Mqtt channel adapter for publish, " +
                "url=[{}], pubClientId=[{}]", url, pubClientId);
        return messageHandler;
    }

    @Bean
    public MessageChannel mqttOutboundChannel() {
        return new DirectChannel();
    }

    ///
    // public functions
    ///
    public void addTopic(String... topics) {
        this.adapter.addTopic(topics);
    }

    public void removeTopic(String... topics) {
        this.adapter.removeTopic(topics);
    }

    ///
    // private functions
    ///
    private String createMqttClientId(boolean publish) {
        String moduleName = Module.getName();
        if (StringUtils.isBlank(moduleName)) {
            moduleName = "iot_mqtt";
        }
        moduleName += publish ? "_pub_" : "_sub_";
        return moduleName + RandomStringUtils.randomAlphanumeric(8).toLowerCase();
    }
}

        MqttSender

package org.thingsboard.server.transport.emqx.config;

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;

/**
 * @author zhangzhixiang on 2023/4/12
 */
@Component
@MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
public interface MqttSender {

    void sendToMqtt(String data);

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

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

        到此SpringBoot 集成 Emqx 发布/订阅数据介绍完成。