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【Java】基于NIO的多线程服务器端

作者:Burning_BL / 发布于2013/7/1/ 490

在连接数很大的情况下，使用Selector能减少并发线程数，减少上下文切换的消耗，非阻塞IO使得具备流程的读写。


	package main;

	import java.io.IOException;
	import java.net.InetSocketAddress;
	import java.net.ServerSocket;
	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;
	import java.util.concurrent.ExecutorService;
	import java.util.concurrent.Executors;

	public class Server {
	private final int PORT = 1234;
	private ExecutorService pool;
	private ServerSocketChannel ssc;
	private Selector selector;
	private static Charset charset = Charset.forName("utf-8");
	private int n;
	
	public static void main(String[] args) throws IOException{
	 Server server = new Server();
	 server.doService();
	}
	
	public Server() throws IOException{
	 pool = Executors.newFixedThreadPool(5);
	
	 ssc = ServerSocketChannel.open();
	 ssc.configureBlocking(false);
	 ServerSocket ss = ssc.socket();
	 ss.bind(new InetSocketAddress(PORT));
	 selector = Selector.open();
	 ssc.register(selector,SelectionKey.OP_ACCEPT);
	 System.out.println("Server started...");
	}
	
	public void doService(){
	 while(true){
	 try{
	 n = selector.select();
	 }catch (IOException e) {
	 throw new RuntimeException("Selector.select()异常!");
	 }
	 if(n==0)
	 continue;
	 Set<SelectionKey> keys = selector.selectedKeys();
	 Iterator<SelectionKey> iter = keys.iterator();
	 while(iter.hasNext()){
	 SelectionKey key = iter.next();
	 iter.remove();
	 if(key.isAcceptable()){
	 SocketChannel sc = null;
	 try{
	 sc = ((ServerSocketChannel)key.channel()).accept();
	 sc.configureBlocking(false);
	 System.out.println("客户端:"+sc.socket().getInetAddress().getHostAddress()+" 已连接");
	 SelectionKey k = sc.register(selector, SelectionKey.OP_READ);
	 ByteBuffer buf = ByteBuffer.allocate(1024);
	 k.attach(buf);
	 }catch (Exception e) {
	 try{
	 sc.close();
	 }catch (Exception ex) {
	 }
	 }
	 }
	 else if(key.isReadable()){
	 key.interestOps(key.interestOps()&(~SelectionKey.OP_READ));
	 pool.execute(new Worker(key));
	 }
	 }
	 }
	}
	
	public static class Worker implements Runnable{
	 private SelectionKey key;
	 public Worker(SelectionKey key){
	 this.key = key;
	 }
	
	 @Override
	 public void run() {
	 SocketChannel sc = (SocketChannel)key.channel();
	 ByteBuffer buf = (ByteBuffer)key.attachment();
	 buf.clear();
	 int len = 0;
	 try{
	 while((len=sc.read(buf))>0){//非阻塞，立刻读取缓冲区可用字节
	 buf.flip();
	 System.out.println("客户端："+charset.decode(buf).toString());
	 buf.clear();
	 }
	 if(len==-1){
	 System.out.println("客户端断开。。。");
	 sc.close();
	 }
	 //没有可用字节,继续监听OP_READ
	 key.interestOps(key.interestOps()|SelectionKey.OP_READ);
	 key.selector().wakeup();
	 }catch (Exception e) {
	 try {
	 sc.close();
	 } catch (IOException e1) {
	 }
	 }
	 }
	}
	}

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　多线程服务器　

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