Java NIO Channel 使用详情

public static void main(String[] args) throws ioException {
  // 创建一个输入流
  FileInputStream fileInputStream = new FileInputStream("test-file.txt");
  // 通过输入流获取到 channel
  FileChannel fileChannel = fileInputStream.getChannel();

  // 准备好 ByteBuffer
  ByteBuffer buffer = ByteBuffer.allocate(16);
  // 将 输入流 的 channel 的数据读入 buffer 中
  fileChannel.read(buffer);

  // 简单打印 buffer 的内容
  printBuffer(buffer); // shDEQuanZhanBiJi
}

public static void main(String[] args) throws IOException {
  // 指定需要生成的文件名称
  String generateFileName = "generate-file.txt";
  // 创建一个输出流
  FileOutputStream fileOutputStream = new FileOutputStream(generateFileName);
  // 通过输出流获取到 channel
  FileChannel fileChannel = fileOutputStream.getChannel();

  // 准备好 ByteBuffer, 并向里面写入数据
  ByteBuffer buffer = ByteBuffer.allocate(16);
  buffer.put("shDEQuanZhanBiJi".getBytes(StandardCharsets.UTF_8));

  // 将 输入流 的 channel 的数据读入 buffer 中
  fileChannel.write(buffer);
  fileChannel.close();
}

public static void main(String[] args) throws IOException {
  // 指定需要生成的文件名称
  String generateFileName = "generate-file.txt";
  // 创建一个输出流
  FileOutputStream fileOutputStream = new FileOutputStream(generateFileName);
  // 通过输出流获取到 channel
  FileChannel fileChannel = fileOutputStream.getChannel();

  // 准备好 ByteBuffer, 并向里面写入数据
  ByteBuffer buffer = ByteBuffer.allocate(16);
  buffer.put("shDEQuanZhanBiJi".getBytes(StandardCharsets.UTF_8));

  // 将 ByteBuffer 切换到读模式
  buffer.flip();
  // 将 输入流 的 channel 的数据读入 buffer 中
  fileChannel.write(buffer);
  
  fileChannel.close();
}

public static void main(String[] args) throws IOException {
  // 指定需要生成的文件名称
  String targetFileName = "target-file.txt";
  // 创建 RandomAccessFile, 赋予可读(r)、可写(w)的权限
  RandomAccessFile accessFile = new RandomAccessFile(targetFileName, "rw");
  FileChannel fileChannel = accessFile.getChannel();

  // 创建 ByteBuffer 并写入数据
  ByteBuffer buffer = ByteBuffer.allocate(16);
  buffer.put("shDEQuanZhanBiJi".getBytes(StandardCharsets.UTF_8));
  // 切换到 buffer 的读模式
  buffer.flip();
  // 调用 write 将 buffer 的数据写入到 channel, channel 再写数据到磁盘文件
  fileChannel.write(buffer);

  // 相当于清空 buffer
  buffer.clear();
  // 将之前写入到 channel 的数据再读入到 buffer
  fileChannel.read(buffer);

  // 打印 buffer 中的内容
  printBuffer(buffer);

  fileChannel.close();
}

public static void main(String[] args) throws IOException {
  // 打开一个 ServerSocketChannel
  ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
  // 绑定 8080 端口
  serverSocketChannel.bind(new InetSocketAddress(8080));

  // 开始接受客户端连接
  SocketChannel socketChannel = serverSocketChannel.accept();
  // 获取连接成功
  System.out.printf("socketChannel %s connected\n", socketChannel);
  // 准备 ByteBuffer 以从 socketChannel 中读取数据
  ByteBuffer buffer = ByteBuffer.allocate(16);

  // 开始读取数据
  System.out.println("before read");
  int read = socketChannel.read(buffer);
  System.out.printf("read complete, read bytes length: %s \n", read);

  printBuffer(buffer);
}

serverSocketChannel.configureBlocking(false);

public static void main(String[] args) throws IOException {
  // 打开一个 SocketChannel
  SocketChannel socketChannel = SocketChannel.open();
  // 连接到 localhost 的 8080 端口
  socketChannel.connect(new InetSocketAddress("localhost", 8080));

  // 准备 ByteBuffer
  ByteBuffer buffer = ByteBuffer.allocate(16);
  buffer.put(Charset.defaultCharset().encode("test"));

  // 将 buffer 切换成读模式 & 向 channel 中写入数据
  buffer.flip();
  socketChannel.write(buffer);
}

socketChannel java.nio.channels.SocketChannel[connected local=/127.0.0.1:8080 remote=/127.0.0.1:64373] connected
before read
read complete, read bytes length: 4 
BUFFER VALUE: test

public static void main(String[] args) throws IOException {
  DatagramChannel datagramChannel = DatagramChannel.open();

  // 构建 buffer 数据
  ByteBuffer buffer = ByteBuffer.allocate(16);
  buffer.put(Charset.defaultCharset().encode("test"));

  // 切换到 buffer 的读模式
  buffer.flip();
  datagramChannel.send(buffer, new InetSocketAddress("localhost", 8080));
}

public static void main(String[] args) throws IOException {
  DatagramChannel datagramChannel = DatagramChannel.open();
  datagramChannel.bind(new InetSocketAddress(8080));

  ByteBuffer buffer = ByteBuffer.allocate(16);
  datagramChannel.receive(buffer);

  printBuffer(buffer);
}