BIO和NIO编程(待完善)-编程知识

BIO和NIO编程(待完善)

IO模型

BIO

NIO

常见问题

IO模型

Java共支持3种网络编程IO模式：BIO，NIO，AIO

BIO

同步阻塞模型，一个客户端连接对应一个处理线程

代码示例：

Server端：

public class BioServer {private static ExecutorService executorService = Executors.newFixedThreadPool(10);public static void main(String[] args) throws IOException {ServerSocket serverSocket = new ServerSocket(8888);System.out.println("服务器启动成功");while (true) {Socket socket = serverSocket.accept();System.out.println("客户端连接成功");executorService.execute(() -> {try (BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()))) {String message;while ((message = reader.readLine()) != null) {System.out.println("收到消息: " + message);writer.write("已收到消息: " + message);writer.newLine();writer.flush();}} catch (IOException e) {e.printStackTrace();}});}}
}

Client端：

public class BioClient {public static void main(String[] args) throws IOException {Socket socket = new Socket("localhost", 8888);BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));BufferedReader consoleReader = new BufferedReader(new InputStreamReader(System.in));String message;while ((message = consoleReader.readLine()) != null) {writer.write(message);writer.newLine();writer.flush();System.out.println("发送消息: " + message);System.out.println("收到回复: " + reader.readLine());}socket.close();}
}

执行结果：

存在问题：

IO操作是阻塞操作，连接时读写会造成线程阻塞
线程太多会造成CPU异常

应用场景：

BIO 方式适用连接数较小且固定的架构，这种方式对服务器资源要求比较高，但代码简单易理解。

NIO

同步非阻塞，服务器实现模式为一个线程可以处理多个请求(连接)，客户端发送的连接请求都会注册到多路复用器selector上，多路复用器轮询到连接有IO请求就进行处理，JDK1.4开始引入。

应用场景：

NIO方式适用于连接数目多且连接比较短（轻操作）的架构，如聊天服务器，弹幕系统，服务器间通讯，编程比较复杂。

代码

public class BioSelectorServer {public static void main(String[] args) throws IOException {ServerSocketChannel serverSocket = ServerSocketChannel.open();serverSocket.socket().bind(new InetSocketAddress(9000));// 设置非阻塞serverSocket.configureBlocking(false);// 创建多路复用器Selector selector = Selector.open();// 注册serversocket到selector， 关注连接事件serverSocket.register(selector, SelectionKey.OP_ACCEPT);System.out.println("服务启动成功");while (true) {// 阻塞等待需要处理的事件selector.select();Set<SelectionKey> selectionKeys = selector.selectedKeys();Iterator<SelectionKey> iterator = selectionKeys.iterator();while (iterator.hasNext()) {SelectionKey key = iterator.next();// 如果是连接事件  > 获取连接并且注册读事件if (key.isAcceptable()) {ServerSocketChannel server = (ServerSocketChannel) key.channel();SocketChannel socketChannel = server.accept();socketChannel.configureBlocking(false);socketChannel.register(selector, SelectionKey.OP_READ);System.out.println("客户端连接成功");} else if (key.isReadable()) {SocketChannel socketChannel = (SocketChannel) key.channel();ByteBuffer byteBuffer = ByteBuffer.allocate(128);int len = socketChannel.read(byteBuffer);if (len > 0) {System.out.println("接收到消息:" + new String(byteBuffer.array()));} else {System.out.println("客户端断开连接");socketChannel.close();}}// 从事件集合里删除本次处理的key，防止下次select重复处理iterator.remove();}}}
}

NIO的三大核心组件: