java实现网络代理

要实现Java网络代理，可以使用Java提供的Socket类和ServerSocket类。以下是一个简单的示例代码：

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class ProxyServer {
    private static final int PROXY_PORT = 8080;
    private static final String TARGET_HOST = "目标主机的IP地址";
    private static final int TARGET_PORT = 80;

    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(PROXY_PORT);

            while (true) {
                Socket clientSocket = serverSocket.accept();

                Thread proxyThread = new Thread(() -> {
                    try {
                        // 连接目标主机
                        Socket targetSocket = new Socket(TARGET_HOST, TARGET_PORT);

                        // 处理客户端请求
                        Thread clientThread = new Thread(() ->
                                handleRequest(clientSocket.getInputStream(), targetSocket.getOutputStream()));
                        clientThread.start();

                        // 处理目标主机响应
                        handleResponse(targetSocket.getInputStream(), clientSocket.getOutputStream());

                        // 等待线程完成
                        clientThread.join();

                        // 关闭连接
                        targetSocket.close();
                        clientSocket.close();
                    } catch (IOException | InterruptedException e) {
                        e.printStackTrace();
                    }
                });

                proxyThread.start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void handleRequest(InputStream clientInput, OutputStream targetOutput) {
        try {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = clientInput.read(buffer)) != -1) {
                targetOutput.write(buffer, 0, bytesRead);
                targetOutput.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void handleResponse(InputStream targetInput, OutputStream clientOutput) {
        try {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = targetInput.read(buffer)) != -1) {
                clientOutput.write(buffer, 0, bytesRead);
                clientOutput.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}