java mqtt监听homeassistant推送

可以使用 Eclipse Paho MQTT 客户端库来实现 Java MQTT 监听 HomeAssistant 推送的功能。以下是一个简单的示例代码：

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class MqttListener {
    public static void main(String[] args) {
        String broker = "tcp://localhost:1883";
        String clientId = "JavaMqttListener";
        MemoryPersistence persistence = new MemoryPersistence();

        try {
            MqttClient mqttClient = new MqttClient(broker, clientId, persistence);
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setCleanSession(true);
            System.out.println("Connecting to broker: " + broker);
            mqttClient.connect(connOpts);
            System.out.println("Connected");

            String topic = "homeassistant/#";
            int qos = 0;
            mqttClient.subscribe(topic, qos);
            System.out.println("Subscribed to topic: " + topic);

            mqttClient.setCallback(new MqttCallback() {
                public void connectionLost(Throwable cause) {
                    System.out.println("Connection lost: " + cause.getMessage());
                }

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

                public void deliveryComplete(IMqttDeliveryToken token) {
                    System.out.println("Delivery complete");
                }
            });
        } catch (MqttException me) {
            System.out.println("Reason: " + me.getReasonCode());
            System.out.println("Message: " + me.getMessage());
            System.out.println("Loc: " + me.getLocalizedMessage());
            System.out.println("Cause: " + me.getCause());
            System.out.println("Excep: " + me);
        }
    }
}

这个代码片段使用 Eclipse Paho MQTT 客户端库来连接到本地的 MQTT 代理，并订阅了 "homeassistant/#" 主题。当有消息到达时，会打印出消息内容。