spring 集成mqtt 物联网通信

要在Spring中集成MQTT进行物联网通信，可以使用Eclipse Paho MQTT客户端库。以下是集成步骤：

1. 添加Paho依赖

在pom.xml中添加以下依赖：

<dependency>
    <groupId>org.eclipse.paho</groupId>
    <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
    <version>1.2.0</version>
</dependency>

2. 创建MQTT配置类

创建一个类来配置MQTT连接的参数，例如主机名、端口号、用户名、密码等。

@Configuration
public class MqttConfig {

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

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

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

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

    @Bean
    public MqttConnectOptions mqttConnectOptions() {
        MqttConnectOptions options = new MqttConnectOptions();
        options.setCleanSession(true);
        options.setUserName(username);
        options.setPassword(password.toCharArray());
        return options;
    }

    @Bean
    public MqttClient mqttClient() throws MqttException {
        return new MqttClient(brokerUrl, clientId);
    }
}

3. 创建MQTT服务类

创建一个类来发送和接收MQTT消息。在该类中，可以注入MqttClient和MqttConnectOptions。

@Service
public class MqttService {

    @Autowired
    private MqttClient mqttClient;

    @Autowired
    private MqttConnectOptions mqttConnectOptions;

    public void sendMessage(String topic, String message) throws MqttException {
        MqttMessage mqttMessage = new MqttMessage(message.getBytes());
        mqttClient.connect(mqttConnectOptions);
        mqttClient.publish(topic, mqttMessage);
        mqttClient.disconnect();
    }

    public void subscribe(String topic, MqttCallback callback) throws MqttException {
        mqttClient.connect(mqttConnectOptions);
        mqttClient.setCallback(callback);
        mqttClient.subscribe(topic);
    }
}

4. 发送MQTT消息

在需要发送MQTT消息的地方，注入MqttService并调用sendMessage方法。

@Autowired
private MqttService mqttService;

public void sendMqttMessage(String topic, String message) throws MqttException {
    mqttService.sendMessage(topic, message);
}

5. 接收MQTT消息

实现MqttCallback接口，并在subscribe方法中将其传递给MqttClient。当收到MQTT消息时，会回调messageArrived方法。

@Component
public class MyMqttCallback implements MqttCallback {

    @Override
    public void connectionLost(Throwable throwable) {
        // 连接丢失
    }

    @Override
    public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
        // 收到消息
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
        // 消息发送完成
    }
}

@Autowired
private MqttService mqttService;

@Autowired
private MyMqttCallback myMqttCallback;

public void subscribeMqttMessage(String topic) throws MqttException {
    mqttService.subscribe(topic, myMqttCallback);
}

以上是在Spring中集成MQTT进行物联网通信的基本步骤。需要注意的是，MQTT是基于TCP协议的，因此需要确保网络通畅。另外，MQTT的QoS级别有三个，分别是0、1和2，不同的级别会影响消息的可靠性和传输效率，需要根据实际情况进行选择。