已通过Chrome测试WebSocket，如何用Java实现访问并打印响应？

下面提供两种常用的Java实现方案，实现你给出的JS代码功能：连接指定WebSocket服务端，接收消息并打印。

方案一：Java 11+原生WebSocket API #

JDK 11及以上版本自带了WebSocket客户端API，无需额外依赖：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.WebSocket;
import java.util.concurrent.CompletionStage;

public class NativeWebSocketClient {
    public static void main(String[] args) {
        // 替换为你的WebSocket地址
        String wsUrl = "ws://address:port";

        HttpClient client = HttpClient.newHttpClient();
        WebSocket webSocket = client.newWebSocketBuilder()
                .buildAsync(URI.create(wsUrl), new WebSocket.Listener() {
                    // 接收消息时触发，对应JS的onmessage
                    @Override
                    public CompletionStage<?> onText(WebSocket webSocket, CharSequence data, boolean last) {
                        System.out.println("收到消息: " + data);
                        return WebSocket.Listener.super.onText(webSocket, data, last);
                    }

                    @Override
                    public void onOpen(WebSocket webSocket) {
                        System.out.println("WebSocket连接已建立");
                        WebSocket.Listener.super.onOpen(webSocket);
                    }

                    @Override
                    public CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason) {
                        System.out.println("WebSocket连接关闭，状态码: " + statusCode + ", 原因: " + reason);
                        return WebSocket.Listener.super.onClose(webSocket, statusCode, reason);
                    }

                    @Override
                    public void onError(WebSocket webSocket, Throwable error) {
                        System.err.println("WebSocket发生错误: " + error.getMessage());
                        WebSocket.Listener.super.onError(webSocket, error);
                    }
                })
                .join();

        // 保持主线程存活，避免程序退出
        try {
            Thread.currentThread().join();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }
}

方案二：使用OkHttp库 #

OkHttp是常用的HTTP客户端库，WebSocket实现简洁易用，需先引入依赖：

Maven依赖 #

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>4.12.0</version> <!-- 使用最新稳定版即可 -->
</dependency>

客户端代码 #

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.WebSocket;
import okhttp3.WebSocketListener;
import okio.ByteString;

public class OkHttpWebSocketClient {
    public static void main(String[] args) {
        String wsUrl = "ws://address:port";

        OkHttpClient client = new OkHttpClient();

        Request request = new Request.Builder().url(wsUrl).build();
        WebSocketListener listener = new WebSocketListener() {
            // 对应JS的onmessage
            @Override
            public void onMessage(WebSocket webSocket, String text) {
                System.out.println("收到消息: " + text);
            }

            @Override
            public void onMessage(WebSocket webSocket, ByteString bytes) {
                // 处理二进制消息，如果服务端有发送的话
                System.out.println("收到二进制消息: " + bytes.hex());
            }

            @Override
            public void onOpen(WebSocket webSocket, okhttp3.Response response) {
                System.out.println("WebSocket连接已建立");
            }

            @Override
            public void onClosed(WebSocket webSocket, int code, String reason) {
                System.out.println("WebSocket连接关闭，状态码: " + code + ", 原因: " + reason);
            }

            @Override
            public void onFailure(WebSocket webSocket, Throwable t, okhttp3.Response response) {
                System.err.println("WebSocket发生错误: " + t.getMessage());
            }
        };

        WebSocket webSocket = client.newWebSocket(request, listener);

        // 保持主线程存活
        try {
            Thread.currentThread().join();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }
}

内容的提问来源于stack exchange，提问作者Alessandro Provenzano