简单的网络文件共享系统的设计与实现。使用Java代码呈现

网络文件共享系统的设计与实现可以分为以下几个步骤：

1. 设计文件共享协议：定义客户端和服务端之间交互的消息格式和规则。
2. 实现服务端：服务端需要监听客户端的请求，并响应请求。当接收到文件上传请求时，服务端需要将文件保存到指定的位置，并返回上传成功的消息。当接收到文件下载请求时，服务端需要读取指定的文件并将文件数据返回给客户端。
3. 实现客户端：客户端需要向服务端发送请求，并处理服务端响应。当上传文件时，客户端需要将文件数据打包成消息发送给服务端，等待服务端的响应。当下载文件时，客户端需要向服务端发送下载请求，并将接收到的文件数据保存到本地。

以下是一个简单的网络文件共享系统的Java实现：

文件共享协议：

public class Protocol {
    // 消息类型常量
    public static final int UPLOAD_REQUEST = 1; // 上传请求
    public static final int UPLOAD_RESPONSE = 2; // 上传响应
    public static final int DOWNLOAD_REQUEST = 3; // 下载请求
    public static final int DOWNLOAD_RESPONSE = 4; // 下载响应
    
    // 消息格式：消息类型 + 文件名 + 文件数据
    public static byte[] encode(int type, String fileName, byte[] data) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        DataOutputStream dataOut = new DataOutputStream(out);
        dataOut.writeInt(type);
        dataOut.writeUTF(fileName);
        dataOut.writeInt(data.length);
        dataOut.write(data);
        return out.toByteArray();
    }
    
    // 解析消息
    public static Message decode(byte[] data) throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream(data);
        DataInputStream dataIn = new DataInputStream(in);
        int type = dataIn.readInt();
        String fileName = dataIn.readUTF();
        int length = dataIn.readInt();
        byte[] fileData = new byte[length];
        dataIn.readFully(fileData);
        return new Message(type, fileName, fileData);
    }
    
    // 消息类
    public static class Message {
        public int type;
        public String fileName;
        public byte[] data;
        
        public Message(int type, String fileName, byte[] data) {
            this.type = type;
            this.fileName = fileName;
            this.data = data;
        }
    }
}

服务端：

public class Server {
    private ServerSocket serverSocket;
    
    public Server(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }
    
    public void start() throws IOException {
        while (true) {
            Socket socket = serverSocket.accept();
            Thread t = new Thread(new ClientHandler(socket));
            t.start();
        }
    }
    
    private class ClientHandler implements Runnable {
        private Socket socket;
        
        public ClientHandler(Socket socket) {
            this.socket = socket;
        }
        
        @Override
        public void run() {
            try {
                InputStream in = socket.getInputStream();
                OutputStream out = socket.getOutputStream();
                byte[] buffer = new byte[1024];
                int len = in.read(buffer);
                Protocol.Message request = Protocol.decode(Arrays.copyOf(buffer, len));
                if (request.type == Protocol.UPLOAD_REQUEST) { // 处理上传请求
                    FileOutputStream fileOut = new FileOutputStream(request.fileName);
                    fileOut.write(request.data);
                    fileOut.close();
                    Protocol.Message response = new Protocol.Message(Protocol.UPLOAD_RESPONSE, request.fileName, null);
                    out.write(Protocol.encode(response.type, response.fileName, response.data));
                } else if (request.type == Protocol.DOWNLOAD_REQUEST) { // 处理下载请求
                    FileInputStream fileIn = new FileInputStream(request.fileName);
                    byte[] data = new byte[fileIn.available()];
                    fileIn.read(data);
                    fileIn.close();
                    Protocol.Message response = new Protocol.Message(Protocol.DOWNLOAD_RESPONSE, request.fileName, data);
                    out.write(Protocol.encode(response.type, response.fileName, response.data));
                }
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端：

public class Client {
    private String serverHost;
    private int serverPort;
    
    public Client(String serverHost, int serverPort) {
        this.serverHost = serverHost;
        this.serverPort = serverPort;
    }
    
    public void upload(String fileName) throws IOException {
        FileInputStream fileIn = new FileInputStream(fileName);
        byte[] data = new byte[fileIn.available()];
        fileIn.read(data);
        fileIn.close();
        Protocol.Message request = new Protocol.Message(Protocol.UPLOAD_REQUEST, fileName, data);
        Socket socket = new Socket(serverHost, serverPort);
        OutputStream out = socket.getOutputStream();
        out.write(Protocol.encode(request.type, request.fileName, request.data));
        byte[] buffer = new byte[1024];
        int len = socket.getInputStream().read(buffer);
        Protocol.Message response = Protocol.decode(Arrays.copyOf(buffer, len));
        if (response.type == Protocol.UPLOAD_RESPONSE) {
            System.out.println("Upload success: " + response.fileName);
        } else {
            System.out.println("Upload failed: " + response.fileName);
        }
        socket.close();
    }
    
    public void download(String fileName) throws IOException {
        Protocol.Message request = new Protocol.Message(Protocol.DOWNLOAD_REQUEST, fileName, null);
        Socket socket = new Socket(serverHost, serverPort);
        OutputStream out = socket.getOutputStream();
        out.write(Protocol.encode(request.type, request.fileName, request.data));
        byte[] buffer = new byte[1024];
        int len = socket.getInputStream().read(buffer);
        Protocol.Message response = Protocol.decode(Arrays.copyOf(buffer, len));
        if (response.type == Protocol.DOWNLOAD_RESPONSE) {
            FileOutputStream fileOut = new FileOutputStream(response.fileName);
            fileOut.write(response.data);
            fileOut.close();
            System.out.println("Download success: " + response.fileName);
        } else {
            System.out.println("Download failed: " + response.fileName);
        }
        socket.close();
    }
}

使用示例：

public class Main {
    public static void main(String[] args) throws IOException {
        // 启动服务端
        Server server = new Server(8000);
        server.start();
        
        // 创建客户端并上传、下载文件
        Client client = new Client("localhost", 8000);
        client.upload("test.txt");
        client.download("test.txt");
    }
}