帮我写一个websocket实现连接到mqtt服务器的java代码

好的，下面是一个基于Java的WebSocket连接MQTT服务器的代码示例：

import java.net.URI;
import java.net.URISyntaxException;
import java.nio.ByteBuffer;
import java.util.Base64;
import java.util.concurrent.CountDownLatch;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.eclipse.paho.client.mqttv3.util.Debug;

import org.java_websocket.WebSocket;
import org.java_websocket.client.WebSocketClient;
import org.java_websocket.handshake.ServerHandshake;

public class MqttWebSocketClient {
    private static final String MQTT_BROKER_URI = "wss://mqtt.example.com";
    private static final String MQTT_CLIENT_ID = "mqtt-websocket-client";
    private static final String MQTT_USERNAME = "your-username";
    private static final String MQTT_PASSWORD = "your-password";

    public static void main(String[] args) {
        try {
            // Create a WebSocket client and connect to the MQTT broker
            WebSocketClient webSocketClient = new WebSocketClient(new URI(MQTT_BROKER_URI)) {
                @Override
                public void onOpen(ServerHandshake handshake) {
                    System.out.println("WebSocket connection established");
                }

                @Override
                public void onMessage(String message) {
                    System.out.println("Received message: " + message);
                }

                @Override
                public void onMessage(ByteBuffer message) {
                    // Convert the binary message to a string and print it
                    byte[] bytes = new byte[message.remaining()];
                    message.get(bytes);
                    String str = Base64.getEncoder().encodeToString(bytes);
                    System.out.println("Received binary message: " + str);
                }

                @Override
                public void onClose(int code, String reason, boolean remote) {
                    System.out.println("WebSocket connection closed: " + reason);
                }

                @Override
                public void onError(Exception ex) {
                    System.out.println("WebSocket connection error: " + ex.getMessage());
                }
            };
            webSocketClient.connect();

            // Wait for the WebSocket connection to be established
            CountDownLatch latch = new CountDownLatch(1);
            while (!webSocketClient.isOpen()) {
                latch.await();
            }

            // Create an MQTT client and connect to the broker over the WebSocket
            MqttConnectOptions connectOptions = new MqttConnectOptions();
            connectOptions.setUserName(MQTT_USERNAME);
            connectOptions.setPassword(MQTT_PASSWORD.toCharArray());

            MqttClient mqttClient = new MqttClient(MQTT_BROKER_URI, MQTT_CLIENT_ID, new MemoryPersistence());
            mqttClient.setCallback(new MqttCallbackHandler());

            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, new TrustManager[] { new X509TrustManager() {
                public void checkClientTrusted(java.security.cert.X509Certificate[] chain, String authType) {
                }

                public void checkServerTrusted(java.security.cert.X509Certificate[] chain, String authType) {
                }

                public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                    return null;
                }
            } }, null);

            SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
            connectOptions.setSocketFactory(sslSocketFactory);

            Debug clientDebug = mqttClient.getDebug();
            clientDebug.dumpClient();
            mqttClient.connect(connectOptions);

            // Subscribe to a topic and publish a message
            mqttClient.subscribe("test/topic");
            mqttClient.publish("test/topic", new MqttMessage("Hello, MQTT over WebSocket!".getBytes()));

            // Wait for the MQTT message to be received
            latch.await();

            // Disconnect from the broker and close the WebSocket client
            mqttClient.disconnect();
            webSocketClient.close();
        } catch (URISyntaxException | InterruptedException | MqttException | Exception ex) {
            System.out.println("Exception: " + ex.getMessage());
        }
    }

    private static class MqttCallbackHandler implements org.eclipse.paho.client.mqttv3.MqttCallback {
        @Override
        public void connectionLost(Throwable cause) {
            System.out.println("MQTT connection lost: " + cause.getMessage());
        }

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

        @Override
        public void deliveryComplete(org.eclipse.paho.client.mqttv3.IMqttDeliveryToken token) {
            System.out.println("MQTT message delivered: " + token.getMessageId());
        }
    }
}

在上面的代码中，我们使用了Java WebSocket API（`org.java_websocket`）来创建WebSocket客户端，并使用Eclipse Paho MQTT客户端库来连接到MQTT服务器。在`main`方法中，我们首先创建一个`WebSocketClient`来连接到MQTT经纪人的WebSocket端点。然后，我们等待WebSocket连接建立，然后创建一个`MqttClient`并使用`MqttConnectOptions`进行连接。我们还使用了一个自定义的`MqttCallbackHandler`来处理MQTT消息。最后，我们订阅一个主题并发布一条消息。在等待MQTT消息时，我们使用一个`CountDownLatch`来阻止主线程退出。在收到MQTT消息后，我们减少`CountDownLatch`的计数器并退出阻塞状态。最后，我们断开与MQTT服务器的连接并关闭WebSocket客户端。