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随着分布式技术的普及和海量数据的增长，io的能力越来越重要，java提供的io模块提供了足够的扩展性来适应。 我是李福春，我在准备面试，今天的问题是： java中的io有哪几种？ java中的io分3类： 1，BIO ,即同步阻塞IO,对应java.io包提供的工具；基于流模型，虽然直观，代码实现也简单，但是扩展性差，消耗资源大，容易成为系统的瓶颈； 2，NIO，同步非阻塞io,对应java.nio包提供的工具，基于io多路复用； 核心类： Channel ,Selector , Buffer , Charset   selector是io多路复用的基础，实现了一个线程高效管理多个客户端连接，通过事件监听处理感兴趣的事件。 3，AIO,即异步非阻塞io, 基于事件和回调

io的类层级

java各种IO的例子

java.io客户端连接服务端例子

package org.example.mianshi.io;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.InetAddress;import java.net.ServerSocket;import java.net.Socket;/** * 说明：传统流式io 客户端连接服务端例子 * @author carter * 创建时间： 2020年03月25日 9:58 下午 **/public class JavaIOApp {    public static void main(String[] args) {        final Server server = new Server();        new Thread(server).start();        try (                Socket socket = new Socket(InetAddress.getLocalHost(), server.getPort());        ) {            final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));            bufferedReader.lines().forEach(System.out::println);        } catch (IOException e) {            e.printStackTrace();        }    }    public static class Server implements Runnable {        private ServerSocket serverSocket;        public int getPort() {            return serverSocket.getLocalPort();        }        @Override        public void run() {            try (ServerSocket serverSocket = new ServerSocket(0);) {                this.serverSocket = serverSocket;                while (true) {                    final Socket socket = serverSocket.accept();                    new RequestHandler(socket).start();                }            } catch (IOException e) {                e.printStackTrace();            }        }        private class RequestHandler extends Thread {            private Socket socket;            public RequestHandler(Socket socket) {                this.socket = socket;            }            @Override            public void run() {                try (                        final PrintWriter printWriter = new PrintWriter(socket.getOutputStream());                ) {                    printWriter.write("hello world");                    printWriter.flush();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

使用连接池优化

package org.example.mianshi.io;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.InetAddress;import java.net.ServerSocket;import java.net.Socket;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * 说明：传统流式io 客户端连接服务端例子 * @author carter * 创建时间： 2020年03月25日 9:58 下午 **/public class ThreadPoolJavaIOApp {    public static void main(String[] args) {        final Server server = new Server();        new Thread(server).start();        try (                Socket socket = new Socket(InetAddress.getLocalHost(), server.getPort());        ) {            final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));            bufferedReader.lines().forEach(System.out::println);        } catch (IOException e) {            e.printStackTrace();        }    }    public static class Server implements Runnable {        private ExecutorService threadPool = Executors.newFixedThreadPool(4);        private ServerSocket serverSocket;        public int getPort() {            return serverSocket.getLocalPort();        }        @Override        public void run() {            try (ServerSocket serverSocket = new ServerSocket(0);) {                this.serverSocket = serverSocket;                while (true) {                    final Socket socket = serverSocket.accept();                    threadPool.submit(new RequestHandler(socket));                }            } catch (IOException e) {                e.printStackTrace();            }finally {                threadPool.shutdown();            }        }        private class RequestHandler implements Runnable {            private Socket socket;            public RequestHandler(Socket socket) {                this.socket = socket;            }            @Override            public void run() {                try (                        final PrintWriter printWriter = new PrintWriter(socket.getOutputStream());                ) {                    printWriter.write("hello world");                    printWriter.flush();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

java.nio例子

package org.example.mianshi.io;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.net.InetAddress;import java.net.InetSocketAddress;import java.net.Socket;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.nio.charset.Charset;/** * 说明：nio的客户端连接服务端例子 * @author carter * 创建时间： 2020年03月25日 10:32 下午 **/public class JavaNioApp {    public static void main(String[] args) {        new Server().start();        try (                Socket socket = new Socket(InetAddress.getLocalHost(), 8888);        ) {            final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));            bufferedReader.lines().forEach(System.out::println);        } catch (IOException e) {            e.printStackTrace();        }    }    public static class Server extends Thread {        @Override        public void run() {            try {                ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();                serverSocketChannel.bind(new InetSocketAddress(InetAddress.getLocalHost(), 8888));                serverSocketChannel.configureBlocking(false);                final Selector selector = Selector.open();                serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);                while (true) {                    selector.select();                    selector.selectedKeys().forEach(selectionKey -> {                        sayHelloWorld((ServerSocketChannel) selectionKey.channel());                    });                }            } catch (IOException e) {                e.printStackTrace();            }        }        private void sayHelloWorld(ServerSocketChannel channel) {            try (SocketChannel socketChannel = channel.accept()) {                socketChannel.write(Charset.defaultCharset().encode("hello world nio"));            } catch (IOException e) {                e.printStackTrace();            }        }    }}


java.nio2例子

package org.example.mianshi.io;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.net.InetAddress;import java.net.InetSocketAddress;import java.net.Socket;import java.nio.channels.AsynchronousServerSocketChannel;import java.nio.channels.AsynchronousSocketChannel;import java.nio.channels.CompletionHandler;import java.nio.charset.Charset;/** * 说明：TODO * @author carter * 创建时间： 2020年03月25日 10:54 下午 **/public class JavaNio2App {    public static void main(String[] args) {        new Server().start();        try (                Socket socket = new Socket(InetAddress.getLocalHost(), 9999);        ) {            final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));            bufferedReader.lines().forEach(System.out::println);        } catch (IOException e) {            e.printStackTrace();        }    }    public static class Server extends Thread {        @Override        public void run() {            try {                AsynchronousServerSocketChannel serverSocketChannel = AsynchronousServerSocketChannel.open()                        .bind(new InetSocketAddress(InetAddress.getLocalHost(), 9999));                serverSocketChannel.accept(serverSocketChannel, new CompletionHandler
   
    () {                    @Override                    public void completed(AsynchronousSocketChannel socketChannel,                                          AsynchronousServerSocketChannel serverSocketChannel1) {//                        serverSocketChannel1.accept(socketChannel, this);                        socketChannel.write(Charset.defaultCharset().encode("hello world nio2 "));                        try {                            socketChannel.close();                        } catch (IOException e) {                            e.printStackTrace();                        }                    }                    @Override                    public void failed(Throwable exc, AsynchronousServerSocketChannel attachment) {                        exc.printStackTrace();                    }                });            } catch (IOException e) {                e.printStackTrace();            }        }    }}
   

本例子暂时无法运行。只为展示过程；

小结

本篇主要介绍了java提供的3中io，即 BIO,NIO,AIO ; 并提供了一些示例代码辅助理解。

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