在Java中，BIO、NIO和AIO代表了不同的I/O操作模式。以下是每个模型的简要描述以及相应的代码示例。
BIO (Blocking I/O)
- 作用：传统阻塞式I/O，适合低并发场景。
- 用法：使用
java.io包中的类，如ServerSocket来监听连接请求，并为每个新连接创建一个新的线程处理读写。
// 创建服务器端的ServerSocket对象，监听8080端口
ServerSocket serverSocket = new ServerSocket(8080);
while (true) {// 阻塞等待客户端连接Socket socket = serverSocket.accept();// 为每个客户端连接创建一个新线程new Thread(new ClientHandler(socket)).start();
}class ClientHandler implements Runnable {private final Socket socket;public ClientHandler(Socket socket) {this.socket = socket;}@Overridepublic void run() {try (BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));PrintWriter out = new PrintWriter(socket.getOutputStream(), true)) {String inputLine;while ((inputLine = in.readLine()) != null) {if ("bye".equals(inputLine)) break;out.println("Echo: " + inputLine);}} catch (IOException e) {e.printStackTrace();} finally {try { socket.close(); } catch (IOException e) {}}}
}
NIO (Non-blocking I/O)
- 作用：非阻塞式I/O，适合高并发场景。
- 用法：使用
java.nio包，包括Selector、Channel接口等。
// 创建Selector对象
Selector selector = Selector.open();
// 创建ServerSocketChannel并配置为非阻塞模式
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
serverSocketChannel.socket().bind(new InetSocketAddress(8080));
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);while (true) {selector.select(); // 等待就绪事件Set<SelectionKey> selectedKeys = selector.selectedKeys();Iterator<SelectionKey> iterator = selectedKeys.iterator();while (iterator.hasNext()) {SelectionKey key = iterator.next();iterator.remove();if (key.isAcceptable()) {// 处理新的客户端连接ServerSocketChannel ssc = (ServerSocketChannel) key.channel();SocketChannel clientChannel = ssc.accept();clientChannel.configureBlocking(false);clientChannel.register(selector, SelectionKey.OP_READ);} else if (key.isReadable()) {// 处理读取数据SocketChannel clientChannel = (SocketChannel) key.channel();ByteBuffer buffer = ByteBuffer.allocate(256);int bytesRead = clientChannel.read(buffer);if (bytesRead == -1) {clientChannel.close();} else {buffer.flip();byte[] data = new byte[buffer.remaining()];buffer.get(data);System.out.println("Received: " + new String(data, StandardCharsets.UTF_8));buffer.clear();}}}
}
AIO (Asynchronous I/O) 或 NIO.2
- 作用：异步非阻塞式I/O，进一步简化并发编程。
- 用法：从Java 7开始提供的
java.nio.channels.AsynchronousChannel及其子类，例如AsynchronousServerSocketChannel和AsynchronousSocketChannel。
// 创建异步服务器通道
AsynchronousServerSocketChannel serverChannel = AsynchronousServerSocketChannel.open().bind(new InetSocketAddress(8080));// 接受连接请求，设置完成处理器
serverChannel.accept(null, new CompletionHandler<AsynchronousSocketChannel, Void>() {@Overridepublic void completed(AsynchronousSocketChannel result, Void attachment) {// 当接受到新的连接时，再次准备接受下一个连接serverChannel.accept(null, this);// 读取客户端发送的数据result.read(ByteBuffer.allocate(256), result, new CompletionHandler<Integer, AsynchronousSocketChannel>() {@Overridepublic void completed(Integer result, AsynchronousSocketChannel channel) {ByteBuffer buffer = ByteBuffer.allocate(result);try {channel.read(buffer).get();buffer.flip();System.out.println("Received: " + new String(buffer.array(), StandardCharsets.UTF_8));} catch (InterruptedException | ExecutionException e) {e.printStackTrace();}}@Overridepublic void failed(Throwable exc, AsynchronousSocketChannel channel) {try {channel.close();} catch (IOException e) {e.printStackTrace();}}});}@Overridepublic void failed(Throwable exc, Void attachment) {exc.printStackTrace();}
});
请注意，这些代码片段是为了演示目的而简化了错误处理和其他细节。在实际应用中，您需要添加适当的异常处理逻辑，并根据具体需求调整资源管理和业务逻辑。