import java.io.*;import java.net.ServerSocket;import java.net.Socket;import java.util.Scanner;public class FileUploadDownloadExample {// 服务器监听端口private static final int PORT = 8888;// 文件存储目录private static final String FILE_DIR = “files/”;public static void main(String[] args) {// 创建文件存储目录File dir = new File(FILE_DIR);if (!dir.exists()) {dir.mkdirs();}// 启动服务器线程new Thread(FileUploadDownloadExample::startServer).start();// 客户端功能选择Scanner scanner = new Scanner(System.in);while (true) {System.out.println("请选择操作：");System.out.println("1. 上传文件");System.out.println("2. 下载文件");System.out.println("3. 退出");int choice = scanner.nextInt();scanner.nextLine(); // 消耗换行符switch (choice) {case 1:System.out.println("请输入要上传的文件路径：");String uploadFilePath = scanner.nextLine();uploadFile(uploadFilePath);break;case 2:System.out.println("请输入要下载的文件名：");String downloadFileName = scanner.nextLine();downloadFile(downloadFileName);break;case 3:System.out.println("退出程序");System.exit(0);default:System.out.println("无效选择，请重新输入");}}
}// 启动服务器，处理文件上传和下载请求
private static void startServer() {try (ServerSocket serverSocket = new ServerSocket(PORT)) {System.out.println("服务器已启动，监听端口：" + PORT);while (true) {Socket clientSocket = serverSocket.accept();System.out.println("客户端连接：" + clientSocket.getInetAddress());// 为每个客户端创建一个线程处理请求new Thread(() -> handleClient(clientSocket)).start();}} catch (IOException e) {e.printStackTrace();}
}// 处理客户端请求
private static void handleClient(Socket clientSocket) {try (ObjectInputStream ois = new ObjectInputStream(clientSocket.getInputStream());ObjectOutputStream oos = new ObjectOutputStream(clientSocket.getOutputStream())) {// 读取请求类型String requestType = ois.readUTF();if ("upload".equals(requestType)) {// 处理文件上传handleFileUpload(ois);oos.writeUTF("上传成功");} else if ("download".equals(requestType)) {// 处理文件下载String fileName = ois.readUTF();boolean fileExists = handleFileDownload(fileName, oos);if (fileExists) {oos.writeUTF("下载成功");} else {oos.writeUTF("文件不存在");}}} catch (IOException e) {e.printStackTrace();} finally {try {clientSocket.close();} catch (IOException e) {e.printStackTrace();}}
}// 处理文件上传
private static void handleFileUpload(ObjectInputStream ois) throws IOException {// 读取文件名String fileName = ois.readUTF();// 创建文件输出流try (FileOutputStream fos = new FileOutputStream(FILE_DIR + fileName)) {// 读取文件内容byte[] buffer = new byte[4096];int bytesRead;while ((bytesRead = ois.read(buffer)) != -1) {fos.write(buffer, 0, bytesRead);}}System.out.println("文件上传成功：" + fileName);
}// 处理文件下载
private static boolean handleFileDownload(String fileName, ObjectOutputStream oos) throws IOException {File file = new File(FILE_DIR + fileName);if (!file.exists()) {return false;}// 发送文件名oos.writeUTF(fileName);// 发送文件内容try (FileInputStream fis = new FileInputStream(file)) {byte[] buffer = new byte[4096];int bytesRead;while ((bytesRead = fis.read(buffer)) != -1) {oos.write(buffer, 0, bytesRead);}}System.out.println("文件下载成功：" + fileName);return true;
}// 客户端上传文件
private static void uploadFile(String filePath) {File file = new File(filePath);if (!file.exists()) {System.out.println("文件不存在：" + filePath);return;}try (Socket socket = new Socket("localhost", PORT);ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());FileInputStream fis = new FileInputStream(file)) {// 发送上传请求oos.writeUTF("upload");oos.flush();// 发送文件名oos.writeUTF(file.getName());oos.flush();// 发送文件内容byte[] buffer = new byte[4096];int bytesRead;while ((bytesRead = fis.read(buffer)) != -1) {oos.write(buffer, 0, bytesRead);}oos.flush();// 接收服务器响应System.out.println(ois.readUTF());} catch (IOException e) {e.printStackTrace();}
}// 客户端下载文件
private static void downloadFile(String fileName) {try (Socket socket = new Socket("localhost", PORT);ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());ObjectInputStream ois = new ObjectInputStream(socket.getInputStream())) {// 发送下载请求oos.writeUTF("download");oos.flush();// 发送文件名oos.writeUTF(fileName);oos.flush();// 接收服务器响应String response = ois.readUTF();if ("文件不存在".equals(response)) {System.out.println(response);return;}// 创建文件输出流try (FileOutputStream fos = new FileOutputStream("downloads/" + fileName)) {// 创建下载目录File dir = new File("downloads/");if (!dir.exists()) {dir.mkdirs();}// 接收文件内容byte[] buffer = new byte[4096];int bytesRead;while ((bytesRead = ois.read(buffer)) != -1) {fos.write(buffer, 0, bytesRead);}}System.out.println("文件下载成功：" + fileName);} catch (IOException e) {e.printStackTrace();}
}}