使用Java实现HTTP和HTTPS代理服务详解

public static void main(String[] args) {
    try {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("Server started, waiting for client...");
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("Client connected: " + socket.getInetAddress().getHostAddress());
            new Thread(()->{
                try(InputStream inputStream = socket.getInputStream()) {
                    BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                    while (reader.ready()){
                        System.out.println(reader.readLine());
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

//替换域名部分，将http://www.baidu.com 变成 /
private static String replaceDomain(String line) {
    String reqUrl = line.split("\s+")[1];
    //http://www.baidu.com/
    // 提取域名部分
    int endIndex = reqUrl.indexOf("/", 8); // 从第 8 个字符开始搜索斜杠
    String domain = endIndex != -1 ? reqUrl.substring(0, endIndex + 1) : reqUrl;
    // 替换
    return line.replaceFirst(domain, "/");
}
//Connection部分，将Proxy-Connection 变成 Connection
private static String replaceConnection(String line) {
    String prefix = "Proxy-Connection: ";
    return line.replaceFirst(prefix, "Connection: ");
}

private static Object[] getHeader(String str) {
    String hostPrefix = "Host: ";
    String contentLengthPrefix = "Content-Length: ";
    String host = null;
    Integer contentLength = null;
    String[] line = str.split("\r\n");
    for (String l : line) {
        if (l.startsWith(hostPrefix)) {
            host = l.substring(hostPrefix.length());
        } else if (l.startsWith(contentLengthPrefix)) {
            contentLength = Integer.parseInt(l.substring(contentLengthPrefix.length()));
        }
    }
    return new Object[]{host, contentLength};
}

//获取host
String address = (String) getHeader(sb.toString())[0];
//分割host和端口
String[] split = address.split(":");
String host = split[0];
int port = split.length > 1 ? Integer.parseInt(split[1]) : 80;
System.out.println(sb.toString());
//初始化socket连接
socket = new Socket(host, port);
//写入第一次请求的数据
socket.getOutputStream().write(sb.toString().getBytes());

//创建新线程执行socket读取
Socket finalSocket = socket;
new Thread(() -> {
    try {
        InputStream socketInputStream = finalSocket.getInputStream();

        byte[] socketBt = new byte[1024];
        int socketlen = -1;
        while ((socketlen = socketInputStream.read(socketBt)) != -1) {
            System.out.println(new String(socketBt, 0, socketlen));
            clientSocket.getOutputStream().write(socketBt, 0, socketlen);
        }
        socketInputStream.close();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            finalSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}).start();

InputStream inputStream = clientSocket.getInputStream();
StringBuilder sb = new StringBuilder();
byte[] bt = new byte[1024];
int len = -1;
boolean isFirstLine = true;
int contentLength = -1;
while ((len = inputStream.read(bt)) != -1) {
    
    //第一次请求
    if (socket == null) {

        if (isFirstLine) {
            isFirstLine = false;

            String replace = replaceDomain(bt, len);
            
            //跳过HTTPS连接
            if (replace.startsWith("CONNECT")) {
                len = -1;
                break;
            }
            sb.append(replace);
        } else {
            sb.append(new String(bt, 0, len));
        }
        if (contentLength == -1) {
            Integer length = (Integer) getHeader(new String(bt, 0, len))[1];
            if (length != null) {
                contentLength = length;
            }
            int crlfcrlf = findCRLFCRLF(bt, len) + 4;
            contentLength -= (len - crlfcrlf);
        }
        //长度到达结束
        if (contentLength == 0) {
            break;
        }
        if (sb.toString().endsWith("\r\n\r\n")) {
            break;
        }
    } else {
        //首行需要修改
        if (isFirstLine) {
            String replace = replaceDomain(bt, len);
            socket.getOutputStream().write(replace.getBytes());
        } else {
            socket.getOutputStream().write(bt, 0, len);
        }
    }
}

if __name__ == '__main__':
    # 定义服务器的端口
    PORT = 8000
    # 创建请求处理程序
    Handler = http.server.SimpleHTTPRequestHandler
    # 设置工作目录
    os.chdir("C:\Windows\Media")
    # 创建服务器
    with socketserver.TCPServer(("", PORT), Handler) as httpd:
        print(f"服务启动在端口 {PORT}")
        httpd.serve_forever()