最近看了《netty in action》，关于netty的线程模型不太理解，于是学习了一下java nio的知识，利用java nio写个简单的服务器便于理解。

java nio有3个重要的概念， Channels ，Buffers ，Selectors。通过他们我们可以用单个的线程监听多个数据通道。
java nio可以进行阻塞的io操作，也可以进行非阻塞的io操作，我们更多是用非阻塞式的操作。

参考文章

Java NIO 系列教程

NIO 入门

完整代码.码云

测试工具

USR-TCP232
SocketTool2

服务器端使用两个线程，一个线程负责 accept 连接，另一个线程负责处理 接收到的数据

accept代码

package me.zingon.nioserver;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.concurrent.BlockingQueue;/*** Created by zhidi on 2018-6-29.*/
public class SocketAccepter implements Runnable{private Integer port = 9999;private ServerSocketChannel server=null;//接受到的连接private BlockingQueue<SocketChannel> queue=null;Selector acceptSelector=Selector.open();public SocketAccepter(Integer port, BlockingQueue<SocketChannel> queue) throws IOException {this.port = port;this.queue = queue;}@Overridepublic void run() {try {this.server = ServerSocketChannel.open();//配置为非阻塞this.server.configureBlocking(false);//注册accept事件this.server.register(acceptSelector, SelectionKey.OP_ACCEPT);this.server.bind(new InetSocketAddress(port));System.out.println("服务器在 "+port +"端口启动");} catch (IOException e) {e.printStackTrace();}try {SocketChannel socketChannel=this.server.accept();} catch (IOException e) {e.printStackTrace();}while (true){int count = 0;try {count = acceptSelector.selectNow();} catch (IOException e) {e.printStackTrace();}if(count ==0 ){continue;}Iterator<SelectionKey> iterator = acceptSelector.selectedKeys().iterator();while (iterator.hasNext()){SelectionKey key = iterator.next();ServerSocketChannel ssc = (ServerSocketChannel) key.channel();try {//接受连接SocketChannel sc = ssc.accept();queue.add(sc);System.out.println("服务器接收连接 ：" + sc);} catch (IOException e) {e.printStackTrace();}iterator.remove();}}}
}

处理线程

package me.zingon.nioserver;import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.BlockingQueue;/*** Created by zhidi on 2018-6-29.*/
public class SocketLoop implements Runnable {//已接受连接private BlockingQueue<SocketChannel> queue;//读selectorprivate Selector readSelector=Selector.open();//写selectorprivate Selector writeSelector=Selector.open();private ByteBuffer readBuf=ByteBuffer.allocate(1024*64);private Queue<String> msgQueue=new LinkedList<>();public SocketLoop(BlockingQueue<SocketChannel> queue) throws IOException {this.queue = queue;}@Overridepublic void run() {System.out.println("服务器处理线程启动");while (true){//处理已接收连接registerNewChannel();try {readFromChannels();writeToChannels();} catch (IOException e) {e.printStackTrace();}}}//给socketChannel注册读/写时间private void registerNewChannel(){SocketChannel sc=null;while( (sc = queue.poll()) != null){try {sc.configureBlocking(false);sc.register(readSelector, SelectionKey.OP_READ);sc.register(writeSelector,SelectionKey.OP_WRITE);} catch (ClosedChannelException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}}//从读就绪的channel中读取数据，添加到msgQueue中private void readFromChannels() throws IOException {int count = readSelector.selectNow();if(count == 0){return;}Iterator<SelectionKey> iterator = readSelector.selectedKeys().iterator();while (iterator.hasNext()){SelectionKey key =  iterator.next();if(!key.isValid()){continue;}SocketChannel channel = (SocketChannel) key.channel();try {channel.read(readBuf);readBuf.flip();StringBuilder sb=new StringBuilder();while(readBuf.hasRemaining()) {sb.append((char)readBuf.get());}readBuf.compact();System.out.println(sb.toString());msgQueue.add(sb.toString());} catch (IOException e) {e.printStackTrace();key.cancel();channel.socket().close();channel.close();}iterator.remove();}}//当写就绪并且msgQueue不为空时，将msgQueue中的数据发送给所有写就绪channelprivate void writeToChannels() throws IOException {int count = writeSelector.selectNow();if(count == 0){return;}Iterator<SelectionKey> iterator = writeSelector.selectedKeys().iterator();String msg=msgQueue.poll();while (iterator.hasNext()){SelectionKey key =  iterator.next();if(!key.isValid()){continue;}if(msg == null){iterator.remove();return;}SocketChannel channel = (SocketChannel) key.channel();byte[] asd=(Thread.currentThread().getName()+msg).getBytes();ByteBuffer bf=ByteBuffer.allocate(asd.length);bf.put(asd);bf.flip();while(bf.hasRemaining()) {try {channel.write(bf);} catch (IOException e) {key.cancel();channel.socket().close();channel.close();e.printStackTrace();}}bf.clear();iterator.remove();}}
}