Spring Boot中整合MQTT（1）

1. 添加依赖

在pom.xml中添加Eclipse Paho MQTT客户端依赖：

<dependency>
    <groupId>org.eclipse.paho</groupId>
    <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
    <version>1.2.5</version>
</dependency>

2. 配置MQTT连接参数

在application.properties中配置MQTT参数：

mqtt.broker=tcp://localhost:1883
mqtt.clientId=spring-boot-mqtt
mqtt.username=your-username
mqtt.password=your-password
mqtt.default-topic=test/topic

3. 创建MQTT配置类

配置MqttConnectOptions和MqttClient的Bean，处理连接和订阅：

import org.eclipse.paho.client.mqttv3.*;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MqttConfig {

    @Value("${mqtt.broker}")
    private String brokerUrl;

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

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

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

    @Value("${mqtt.default-topic}")
    private String defaultTopic;

    @Bean
    public MqttConnectOptions mqttConnectOptions() {
        MqttConnectOptions options = new MqttConnectOptions();
        options.setServerURIs(new String[]{brokerUrl});
        options.setUserName(username);
        options.setPassword(password.toCharArray());
        options.setAutomaticReconnect(true); // 自动重连
        options.setCleanSession(true);
        return options;
    }

    @Bean
    public IMqttClient mqttClient(MqttConnectOptions options) throws MqttException {
        IMqttClient client = new MqttClient(brokerUrl, clientId);
        client.setCallback(new MqttCallbackExtended() {
            @Override
            public void connectComplete(boolean reconnect, String serverURI) {
                System.out.println("MQTT Connected!");
                try {
                    // 订阅默认主题
                    client.subscribe(defaultTopic, 1);
                } catch (MqttException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void connectionLost(Throwable cause) {
                System.out.println("MQTT Connection Lost: " + cause.getMessage());
            }

            @Override
            public void messageArrived(String topic, MqttMessage message) {
                System.out.println("Received message: " + new String(message.getPayload()) + " on topic: " + topic);
            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken token) {
                // 消息发布完成处理
            }
        });
        client.connect(options);
        return client;
    }
}

4. 创建消息发布服务

实现消息发布逻辑：

import org.eclipse.paho.client.mqttv3.IMqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class MqttPublisher {

    @Autowired
    private IMqttClient mqttClient;

    public void publish(String topic, String payload, int qos, boolean retained) throws MqttException {
        MqttMessage message = new MqttMessage(payload.getBytes());
        message.setQos(qos);
        message.setRetained(retained);
        mqttClient.publish(topic, message);
    }

    // 重载方法，使用默认QoS和retained标志
    public void publish(String topic, String payload) throws MqttException {
        publish(topic, payload, 1, false);
    }
}

5. 测试MQTT功能

创建REST控制器测试消息发布：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MqttController {

    @Autowired
    private MqttPublisher mqttPublisher;

    @GetMapping("/publish")
    public String publishMessage(@RequestParam String message) {
        try {
            mqttPublisher.publish("test/topic", message);
            return "Message published: " + message;
        } catch (Exception e) {
            return "Error: " + e.getMessage();
        }
    }
}

6. 运行与测试

1. 启动MQTT代理服务器（如Mosquitto）：

   mosquitto -c mosquitto.conf
   

2. 运行Spring Boot应用，访问http://localhost:8080/publish?message=HelloMQTT发送消息。
3. 使用MQTT客户端订阅主题（如MQTT.fx）订阅test/topic，确认接收消息。

7. 处理连接异常和自动重连

• 自动重连已在MqttConnectOptions中配置。
• 连接丢失处理：在connectionLost方法中记录日志，客户端会自动尝试重连。

8. 注意事项

• 线程安全：IMqttClient实例方法线程安全，可直接注入使用。
• 消息处理：在messageArrived中避免耗时操作，建议异步处理。
• 遗言消息：可通过MqttConnectOptions.setWill设置遗言主题和消息。

完整代码示例

参考上述步骤整合代码，确保配置正确，即可在Spring Boot中实现MQTT消息的发布与订阅。