NIO使用的例子

作者：御风逍遥
链接：http://www.jianshu.com/p/a9d030fec081

package nio;

import java.io.IOException; 
import java.net.InetSocketAddress; 
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey; 
import java.nio.channels.Selector; 
import java.nio.channels.ServerSocketChannel; 
import java.nio.channels.SocketChannel; 
import java.util.*; 

public class Server {

    private Selector selector; 
    private ByteBuffer readBuffer = ByteBuffer.allocate(1024); //调整缓存的大小可以看到打印输出的变化 
    private ByteBuffer sendBuffer = ByteBuffer.allocate(1024); //调整缓存的大小可以看到打印输出的变化 

    String str;

    public void start() throws IOException {
        // 打开服务器套接字通道 
        ServerSocketChannel ssc = ServerSocketChannel.open(); 
        // 服务器配置为非阻塞 
        ssc.configureBlocking(false); 
        // 进行服务的绑定 
        ssc.bind(new InetSocketAddress("localhost", 8001));

        // 通过open()方法找到Selector
        selector = Selector.open();
        System.err.println(selector);
        // 注册到selector，等待连接
        ssc.register(selector, SelectionKey.OP_ACCEPT);

        while (!Thread.currentThread().isInterrupted()) { 
            selector.select(); // 线程会在此处阻塞，执行处于阻塞模式的选择操作
            Set keys = selector.selectedKeys(); 
            Iterator keyIterator = keys.iterator(); 
            while (keyIterator.hasNext()) { 
                SelectionKey key = keyIterator.next(); 
                // 判断当前key是否可用，可用的条件是该key没有被取消掉，并且通道选择器都没有关闭 
                if (!key.isValid()) {
                    continue;
                }
                // 判断当前key中包含的通道知否准备好接受一个新的套接字连接
                if (key.isAcceptable()) {  
                    accept(key);
                } else if (key.isReadable()) {
                    read(key);
                } else if (key.isWritable()) {
                    write(key);
                }
                keyIterator.remove(); //该事件已经处理，可以丢弃
            } 
        } 
    }

    private void write(SelectionKey key) throws IOException, ClosedChannelException {
        SocketChannel channel = (SocketChannel) key.channel();
        System.out.println("有数据写入: " + str);
        sendBuffer.clear();
        sendBuffer.put(str.getBytes());
        sendBuffer.flip();
        channel.write(sendBuffer);
        channel.register(selector, SelectionKey.OP_READ);
    }

    private void read(SelectionKey key) throws IOException {
        SocketChannel socketChannel = (SocketChannel) key.channel();
        // 清空buffer，为写入数据做准备
        this.readBuffer.clear();
        int numRead;
        try {
            numRead = socketChannel.read(this.readBuffer);
        } catch (IOException e) {
            // 远程强制关闭连接,取消选择键并关闭通道
            key.cancel();
            socketChannel.close();
            return;
        }
        str = new String(readBuffer.array(), 0, numRead);
        System.out.println("读取到内容： " + str);
        socketChannel.register(selector, SelectionKey.OP_WRITE);
    } 

    private void accept(SelectionKey key) throws IOException {
        // 从key中获取通道的时候需要进行转型
        ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
        // 接受通道中包含的连接
        SocketChannel clientChannel = ssc.accept();
        clientChannel.configureBlocking(false);
        clientChannel.register(selector, SelectionKey.OP_READ); 
        System.out.println("有新的连接产生： " + clientChannel.getRemoteAddress()); 
    } 

    public static void main(String[] args) throws IOException { 
        System.out.println("server started..."); 
        new Server().start(); 
    } 
}

package nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Scanner;
import java.util.Set;

public class Client {

    ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
    ByteBuffer readBuffer = ByteBuffer.allocate(1024);

    public void start() throws IOException {
        // 打开socket通道
        SocketChannel sc = SocketChannel.open();
        // 设置为非阻塞
        sc.configureBlocking(false);
        // 连接服务器地址和端口
        sc.connect(new InetSocketAddress("localhost", 8001));
        // 打开选择器
        Selector selector = Selector.open();
        // 注册连接服务器socket的动作
        sc.register(selector, SelectionKey.OP_CONNECT);

        Scanner scanner = new Scanner(System.in);
        while (true) {
            // 选择一组键，其相应的通道已为 I/O 操作准备就绪
            // 此方法执行处于阻塞模式的选择操作
            selector.select();
            // 返回此选择器的已选择键集
            Set keys = selector.selectedKeys();
            System.out.println("keys=" + keys.size());
            Iterator keyIterator = keys.iterator();
            while (keyIterator.hasNext()) {
                SelectionKey key = keyIterator.next();
                keyIterator.remove();
                // 判断此通道上是否正在进行连接操作
                if (key.isConnectable()) {
                    sc.finishConnect();
                    sc.register(selector, SelectionKey.OP_WRITE);
                    System.out.println("server connected...");
                    break;
                } else if (key.isWritable()) { // 写数据
                    System.out.print("please input message:");
                    String message = scanner.nextLine();
                    // ByteBuffer writeBuffer =
                    // ByteBuffer.wrap(message.getBytes());
                    writeBuffer.clear();
                    writeBuffer.put(message.getBytes());
                    // 将缓冲区各标志复位,因为向里面put了数据标志被改变要想从中读取数据发向服务器,就要复位
                    writeBuffer.flip();
                    sc.write(writeBuffer);

                    // 注册写操作,每个chanel只能注册一个操作，最后注册的一个生效
                    // 如果你对不止一种事件感兴趣，那么可以用“位或”操作符将常量连接起来
                    // int interestSet = SelectionKey.OP_READ |
                    // SelectionKey.OP_WRITE;
                    // 使用interest集合
                    sc.register(selector, SelectionKey.OP_READ);
                    sc.register(selector, SelectionKey.OP_WRITE);
                    sc.register(selector, SelectionKey.OP_READ);

                } else if (key.isReadable()) {// 读取数据
                    System.out.print("receive message:");
                    SocketChannel client = (SocketChannel) key.channel();
                    // 将缓冲区清空以备下次读取
                    readBuffer.clear();
                    int num = client.read(readBuffer);
                    System.out.println(new String(readBuffer.array(), 0, num));
                    // 注册读操作，下一次读取
                    sc.register(selector, SelectionKey.OP_WRITE);
                }
            }
        }
    }

    public static void main(String[] args) throws IOException {
        new Client().start();
    }
}