给我展示Eclipse Paho 提供的 MQTT Java 示例代码并在代码上添加中文注释

以下是Eclipse Paho提供的MQTT Java示例代码，已添加了中文注释。

import org.eclipse.paho.client.mqttv3.DisconnectedBufferOptions;
import org.eclipse.paho.client.mqttv3.IMqttClient;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.IMqttMessageListener;
import org.eclipse.paho.client.mqttv3.IMqttToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttClientPersistence;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttSecurityException;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class MQTTClient implements MqttCallback {

    // MQTT 代理服务器的地址
    private static final String brokerUrl = "tcp://mqtt.eclipseprojects.io:1883";

    // 客户端的ID
    private String clientId = "pahomqttclient";

    // MQTT 代理服务器的连接选项
    private MqttConnectOptions options;

    // MQTT 客户端
    private IMqttClient client;

    // 接收到新消息时的回调函数
    private IMqttMessageListener messageListener;

    /**
     * 创建一个新的 MQTT 客户端
     *
     * @param clientId                 客户端 ID
     * @param cleanSession             是否清除会话
     * @param persistence              持久化模式
     * @param messageListener          接收到新消息时的回调函数
     * @param disconnectedBufferOptions 断开连接时的缓冲区选项
     * @throws MqttException 如果创建MQTT客户端失败
     */
    public MQTTClient(String clientId, boolean cleanSession, MqttClientPersistence persistence, IMqttMessageListener messageListener, DisconnectedBufferOptions disconnectedBufferOptions) throws MqttException {
        this.clientId = clientId;
        this.messageListener = messageListener;

        // 创建MQTT客户端
        client = new MqttClient(brokerUrl, clientId, persistence);

        // 设置断开连接时的缓冲区选项
        client.setBufferOpts(disconnectedBufferOptions);

        // 设置回调函数
        client.setCallback(this);

        // 设置连接选项
        options = new MqttConnectOptions();
        options.setCleanSession(cleanSession);
    }

    /**
     * 连接到 MQTT 代理服务器
     *
     * @throws MqttException 如果连接失败
     */
    public void connect() throws MqttException {
        IMqttToken token = client.connectWithResult(options);
        token.waitForCompletion();
    }

    /**
     * 订阅一个主题
     *
     * @param topic 主题名称
     * @throws MqttException 如果订阅失败
     */
    public void subscribe(String topic) throws MqttException {
        client.subscribe(topic, messageListener);
    }

    /**
     * 向一个主题发布一个消息
     *
     * @param topic   主题名称
     * @param message 消息内容
     * @throws MqttException 如果发布失败
     */
    public void publish(String topic, String message) throws MqttException {
        MqttMessage mqttMessage = new MqttMessage(message.getBytes());
        client.publish(topic, mqttMessage);
    }

    /**
     * 断开与MQTT代理服务器的连接
     *
     * @throws MqttException 如果断开连接失败
     */
    public void disconnect() throws MqttException {
        client.disconnect();
    }

    @Override
    public void connectionLost(Throwable cause) {
        // 与MQTT代理服务器的连接断开时的回调函数
    }

    @Override
    public void messageArrived(String topic, MqttMessage message) throws Exception {
        // 接收到新消息时的回调函数
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
        // 发布消息完成时的回调函数
    }
}

希望这能满足您的需求。