NIO三大核心组件

NIO三大核心组件

package com.io;

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.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;

public class NIOServicer2 {


    public static void main(String[] args) throws IOException {
        NIOServicer2 nIOServicer2 = new NIOServicer2();
        nIOServicer2.start();
    }


    public  void start() throws IOException {

        //1.创建一个选择器
        Selector  selector = Selector.open();

        //2.监听socketChannel
        ServerSocketChannel  serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.bind(new InetSocketAddress(8098));
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);

        //3.将ServerSocketChannel 注册到选择器中
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        System.out.println("服务启动.....");
        for(;;){
            //阻塞 有事件通知解除阻塞
            int readyChannels = selector.select();
            //readyChannels 等于0 表示 没有做好准备
            if(readyChannels  == 0) continue;

            //如果有可用的数量，selector会将所有的channel放入到slectionKey的set集合中
            Set<SelectionKey> selectionKeys = selector.selectedKeys();


            //然后通过迭代器的方式将每个链接展示出来
            Iterator iterator = selectionKeys.iterator();
            //如果存在，则继续
            while (iterator.hasNext()){
                //获取selectionKey实例
                SelectionKey selectionKey = (SelectionKey) iterator.next();
                //移除selectionKey
                iterator.remove();

                //7.根据不同的就绪状态，去处理不同的业务逻辑
                //如果是接入事件
                if(selectionKey.isAcceptable()){
                    acceptHandler(serverSocketChannel,selector);
                }
                //如果是可读事件
                if(selectionKey.isReadable()){
                    readHandler(selectionKey,selector);
                }
            }

        }

    }

    /**
     * 接入事件
     */
    private  void acceptHandler(ServerSocketChannel serverSocketChannel,Selector selector) throws IOException {

        System.out.println("链接成功.....");
        //如果是接入事件，创建socketChannel
        SocketChannel socketChannel = serverSocketChannel.accept();
        //将socketChannel设置为非阻塞模式
        socketChannel.configureBlocking(false);
        //将channel注册到selector上，监听可读事件
        socketChannel.register(selector,SelectionKey.OP_READ);
        //回复客户端信息
        socketChannel.write(Charset.forName("UTF-8").encode("success connection"));
    }

    /**
     * 可读事件
     */
    private void readHandler(SelectionKey selectionKey,Selector selector) throws IOException {
        //要从selectionKey中获取到已经就绪的channel
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
        //创建buffer
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

        //循环读取客户端信息
        String request = "";
        while (socketChannel.read(byteBuffer) > 0){
            //将bufer转成读模式
            byteBuffer.flip();
            //读取buffer中的内容
            request += Charset.forName("UTF-8").decode(byteBuffer);
        }
        /**
         * 将channel再次注册到selector 上，监听他的可读事件
         */
        socketChannel.register(selector,SelectionKey.OP_READ);
        //将消息广播给其他变量
        if(request.length() > 0){
            System.out.println(request);
        }
        //回复客户端信息
        socketChannel.write(Charset.forName("UTF-8").encode("success connection"));
    }
}