Java spring Mqtt

Java Spring 是一个流行的开源框架，用于构建企业级应用程序。MQTT（Message Queuing Telemetry Transport）是一种轻量级的消息传递协议，用于连接物联网设备和传感器等设备。在Java Spring中，可以使用Eclipse Paho客户端库来实现MQTT协议的通信。

以下是使用Java Spring实现MQTT的基本步骤：

1. 添加依赖：在pom.xml文件中添加Eclipse Paho客户端库的依赖项。

2. 创建配置类：创建一个配置类并注入MQTT连接工厂。

3. 创建消息发布者：创建一个消息发布者并注入MQTT连接工厂。

4. 创建消息订阅者：创建一个消息订阅者并注入MQTT连接工厂。

5. 发布消息：使用消息发布者来发布消息。

6. 订阅消息：使用消息订阅者来订阅消息。

下面是一个简单的示例代码：

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

    @Bean
    public MqttClient mqttClient() throws MqttException {
        MqttClient client = new MqttClient("tcp://localhost:1883", "clientId");
        client.connect(mqttConnectOptions());
        return client;
    }

    @Bean
    public MessagePublisher messagePublisher() throws MqttException {
        return new MessagePublisher(mqttClient());
    }

    @Bean
    public MessageSubscriber messageSubscriber() throws MqttException {
        return new MessageSubscriber(mqttClient());
    }
}

public class MessagePublisher {
    private MqttClient mqttClient;

    public MessagePublisher(MqttClient mqttClient) {
        this.mqttClient = mqttClient;
    }

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

public class MessageSubscriber implements MqttCallback {
    private MqttClient mqttClient;

    public MessageSubscriber(MqttClient mqttClient) throws MqttException {
        this.mqttClient = mqttClient;
        this.mqttClient.setCallback(this);
        this.mqttClient.subscribe("test/topic");
    }

    @Override
    public void connectionLost(Throwable throwable) {}

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

    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {}
}

// 发布消息
@Autowired
private MessagePublisher messagePublisher;

messagePublisher.publish("test/topic", "Hello, world!");

// 订阅消息
@Autowired
private MessageSubscriber messageSubscriber;

这是一个基本的Java Spring实现MQTT的示例，具体实现可以根据需求进行修改和扩展。