java 通过socket传来的MappedByteBuffer 用RandomAccessFile随机写入文件块 最后拼接成完整文件 完整代码

以下是一个示例代码，展示了如何使用 `MappedByteBuffer` 和 `RandomAccessFile` 来接收通过 Socket 传来的文件块，并将其按顺序写入磁盘，最终拼接成完整文件。

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;

public class FileReceiver {
    private static final int PORT = 9999;
    private static final String SAVE_PATH = "/path/to/save/file.txt";
    private static final int BUFFER_SIZE = 4096; // 缓冲区大小

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(PORT);
        System.out.println("等待连接...");

        Socket socket = serverSocket.accept();
        System.out.println("连接成功.");

        DataInputStream dataInputStream = new DataInputStream(socket.getInputStream());
        RandomAccessFile randomAccessFile = new RandomAccessFile(SAVE_PATH, "rw");
        FileChannel fileChannel = randomAccessFile.getChannel();

        long fileSize = dataInputStream.readLong();
        long receivedSize = 0;
        while (receivedSize < fileSize) {
            long remaining = fileSize - receivedSize;
            int bufferSize = (int) Math.min(remaining, BUFFER_SIZE);
            MappedByteBuffer buffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, receivedSize, bufferSize);

            int bytesRead = dataInputStream.read(buffer.array(), 0, bufferSize);
            buffer.limit(bytesRead);
            buffer.force();

            receivedSize += bytesRead;
        }

        fileChannel.close();
        randomAccessFile.close();
        dataInputStream.close();
        socket.close();
        serverSocket.close();

        System.out.println("文件接收完成.");
    }
}

这个示例代码创建了一个服务器端，监听指定端口。当客户端连接成功后，服务器端接收文件的大小信息，并通过 `MappedByteBuffer` 和 `RandomAccessFile` 来接收和写入文件块。最后，关闭相关资源并打印完成信息。

请注意，这只是一个简单的示例，实际使用中可能需要添加错误处理、进度显示和其他的功能。