採用Gateway繫結的方式，網上也有采用paho Mqtt client庫實現的，但是比較麻煩。

1. 引入相關依賴

        <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>
 

2.  配置MQTT伺服器基本資訊，在springBoot配置檔案application.yml中配置，新增如下：

#MQTT配置資訊
#MQTT-使用者名稱
spring.mqtt.username=admin
#MQTT-密碼
spring.mqtt.password=password
#MQTT-伺服器連線地址，如果有多個，用逗號隔開，如：tcp://127.0.0.1:61613，tcp://192.168.2.133:61613
spring.mqtt.url=tcp://127.0.0.1:61613
#MQTT-連線伺服器預設客戶端ID
spring.mqtt.client.id=mqttId
#MQTT-預設的訊息推送主題，實際可在呼叫介面時指定
spring.mqtt.default.topic=topic
 

3. 配置MQTT訊息推送配置類，

**
 * 〈一句話功能簡述〉<br> 
 * 〈MQTT傳送訊息配置〉
 *
 * @author AnswerChang
 * @create 2018/6/4
 * @since 1.0.0
 */
@Configuration
@IntegrationComponentScan
public class MqttSenderConfig {

    @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.default.topic}")
    private String defaultTopic;

    @Bean
    public MqttConnectOptions getMqttConnectOptions(){
        MqttConnectOptions mqttConnectOptions=new MqttConnectOptions();
        mqttConnectOptions.setUserName(username);
        mqttConnectOptions.setPassword(password.toCharArray());
        mqttConnectOptions.setServerURIs(new String[]{hostUrl});
        mqttConnectOptions.setKeepAliveInterval(2);
        return mqttConnectOptions;
    }
    @Bean
    public MqttPahoClientFactory mqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        factory.setConnectionOptions(getMqttConnectOptions());
        return factory;
    }
    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel")
    public MessageHandler mqttOutbound() {
        MqttPahoMessageHandler messageHandler =  new MqttPahoMessageHandler(clientId, mqttClientFactory());
        messageHandler.setAsync(true);
        messageHandler.setDefaultTopic(defaultTopic);
        return messageHandler;
    }
    @Bean
    public MessageChannel mqttOutboundChannel() {
        return new DirectChannel();
    }
}
 

4. 配置MqttGateway訊息推送介面類，在sendToMqtt(String data,@Header(MqttHeaders.TOPIC)String topic)介面中，data為傳送的訊息內容，topic為主題。指定topic，則我們的介面可以根據需要，向不同的主題傳送訊息，方便靈活應用。如果不指定，則使用預設配置的主題。

@MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
public interface MqttGateway {
    void sendToMqtt(String data,@Header(MqttHeaders.TOPIC) String topic);
}

5. 最後，寫個介面類測試下功能，用Postman呼叫sendMqtt.do介面，往hello主題傳送訊息，用MQTTLens訂閱hello主題，從下面截圖，可以看出可以正常往MQTT服務傳送訊息了，而且可以訂閱到。

@RestController
@RequestMapping("/test")
public class TestController {

    @Autowired
    private MqttGateway mqttGateway;

    @RequestMapping("/sendMqtt.do")
    public String sendMqtt(String  sendData){
        mqttGateway.sendToMqtt(sendData,"hello");
        return "OK";
    }
}

最後使用Google瀏覽器 MQTTLens外掛進行測試

轉自：

https://blog.csdn.net/qq_41018959/article/details/80592444

https://blog.csdn.net/qq_41018959/article/details/80564347