ServerSocketChannel实现文件上传下载

ServerSocketChannel 是 Java NIO 中用来实现基于 TCP 协议的服务器的核心类之一，可以轻松地实现文件上传和下载。

1. 文件上传

以下是一个简单的文件上传服务器示例代码：

try (ServerSocketChannel serverSocketChannel = ServerSocketChannel.open()) {
    serverSocketChannel.bind(new InetSocketAddress(8080));
    System.out.println("Server started on port 8080.");

    while (true) {
        try (SocketChannel socketChannel = serverSocketChannel.accept()) {
            System.out.println("Client connected from " + socketChannel.getRemoteAddress());

            ByteBuffer buffer = ByteBuffer.allocate(1024);

            // 读取文件名
            socketChannel.read(buffer);
            buffer.flip();
            String fileName = StandardCharsets.UTF_8.decode(buffer).toString();

            // 读取文件内容
            buffer.clear();
            try (FileChannel fileChannel = FileChannel.open(Paths.get(fileName), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
                while (socketChannel.read(buffer) > 0) {
                    buffer.flip();
                    fileChannel.write(buffer);
                    buffer.clear();
                }
            }

            System.out.println("File uploaded: " + fileName);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
} catch (IOException e) {
    e.printStackTrace();
}

客户端代码：

try (SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("localhost", 8080))) {
    Path path = Paths.get("test.txt");
    ByteBuffer buffer = ByteBuffer.allocate(1024);

    // 发送文件名
    buffer.put(path.getFileName().toString().getBytes());
    buffer.flip();
    socketChannel.write(buffer);
    buffer.clear();

    // 发送文件内容
    try (FileChannel fileChannel = FileChannel.open(path)) {
        while (fileChannel.read(buffer) > 0) {
            buffer.flip();
            socketChannel.write(buffer);
            buffer.clear();
        }
    }

    System.out.println("File uploaded.");
} catch (IOException e) {
    e.printStackTrace();
}

2. 文件下载

以下是一个简单的文件下载服务器示例代码：

try (ServerSocketChannel serverSocketChannel = ServerSocketChannel.open()) {
    serverSocketChannel.bind(new InetSocketAddress(8080));
    System.out.println("Server started on port 8080.");

    while (true) {
        try (SocketChannel socketChannel = serverSocketChannel.accept()) {
            System.out.println("Client connected from " + socketChannel.getRemoteAddress());

            ByteBuffer buffer = ByteBuffer.allocate(1024);

            // 读取文件名
            socketChannel.read(buffer);
            buffer.flip();
            String fileName = StandardCharsets.UTF_8.decode(buffer).toString();

            // 发送文件内容
            buffer.clear();
            try (FileChannel fileChannel = FileChannel.open(Paths.get(fileName))) {
                while (fileChannel.read(buffer) > 0) {
                    buffer.flip();
                    socketChannel.write(buffer);
                    buffer.clear();
                }
            }

            System.out.println("File downloaded: " + fileName);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
} catch (IOException e) {
    e.printStackTrace();
}

客户端代码：

try (SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("localhost", 8080))) {
    Path path = Paths.get("test.txt");
    ByteBuffer buffer = ByteBuffer.allocate(1024);

    // 发送文件名
    buffer.put(path.getFileName().toString().getBytes());
    buffer.flip();
    socketChannel.write(buffer);
    buffer.clear();

    // 接收文件内容
    try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
        while (socketChannel.read(buffer) > 0) {
            buffer.flip();
            fileChannel.write(buffer);
            buffer.clear();
        }
    }

    System.out.println("File downloaded.");
} catch (IOException e) {
    e.printStackTrace();
}

以上就是使用 ServerSocketChannel 实现文件上传和下载的简单示例。注意在实际生产环境中需要对代码进行优化和处理可能的异常情况。