Java NIO Demo

Java NIO Demo

    在读Amoeba源码的时候，里面采用java NIO进行通信管理，以前也了解过一些关于这方面的知识但是都不太系统，最近两天抽时间对这块进行一下扫盲。我主要参考以下两篇文章，个人认为这两篇文章还是不错的入门级文章，讲的比较通俗易懂。
1. http://www.ibm.com/developerworks/cn/education/java/j-nio/section11.html
比较系统的讲述了Channel（通道）、Buffer（缓冲区）、position，limit， capacity in buffer等；其示例代码在：
http://code.google.com/p/astudy/source/browse/trunk/applications/astudy/nio/MultiPortEcho.java?spec=svn141&r=141下

2. http://tutorials.jenkov.com/java-nio/index.html
这个站点也是一个不错的入门级别介绍，虽然是e文，但讲解的比较细致。

3.我的demo
这个小例子，模拟了一个echo服务，客户端向echo服务器发送一段信息，echo收到信息后，返回给客户端，然后，连接关闭。代码如下：

/** */ /***************************************/
客户端代码：
package  com.zxl.channel;

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.nio.charset.Charset;
import  java.util.Set;

public   class  EchoClient  {

    /** *//**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        
        
        SocketChannel channel = SocketChannel.open();
        channel.configureBlocking(false);    
        InetSocketAddress s = new InetSocketAddress("localhost",2000);
        channel.connect(s);
        
        Selector selector = Selector.open();
        channel.register(selector, SelectionKey.OP_CONNECT|SelectionKey.OP_READ);
        
        Charset charset=Charset.forName("GBK");
        
        boolean isFinished = false;
        while(!isFinished){
            int num = selector.select();
            if(num>0){
                Set<SelectionKey> keys = selector.selectedKeys();
                for(SelectionKey k:keys){
                    if(k.isConnectable()){
                        SocketChannel sc = (SocketChannel) k.channel();
                        sc.configureBlocking(false);
                        sc.finishConnect();
                        sc.register(selector, SelectionKey.OP_READ);
                
                        ByteBuffer echoBuffer = ByteBuffer.allocate(1024);
                        ByteBuffer info =charset.encode("好了克隆技术杜洛克防水堵漏开发!");
                        echoBuffer.put(info);
                        
                        echoBuffer.flip();    
                    
                        sc.write(echoBuffer);
                        echoBuffer.clear();
                        
                    }else if (k.isValid() && k.isReadable()) {
                        ByteBuffer echoBuffer = ByteBuffer.allocate(1024);
                        SocketChannel sc = (SocketChannel) k.channel();
                        sc.read(echoBuffer);
                        echoBuffer.flip();
                        
                        System.out.println("echo server return:"+charset.decode(echoBuffer).toString());
                        echoBuffer.clear();
                        
                        isFinished = true;
                        
                        k.cancel();
                        sc.close();
                        selector.close();
                    }
                }
            }    
        }
    }
}

/** */ /*********************************************/
服务端代码：

package  com.zxl.channel;


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;

public   class  MultiPortEchoServer  {

    private Charset charset=Charset.forName("GBK");
    
    private int[] ports;
    
    /** *//**
     * @param args
     */
    public static void main(String[] args) {
        
        int[] ps = {2000,2001};   //默认监听2000,2001端口
        
        new MultiPortEchoServer(ps);

    }
    
    public MultiPortEchoServer(int[] ports){
        this.ports = ports;
        try {
            go();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public void go() throws IOException{
        
        Selector selector = Selector.open();
        
        for(int i=0;i<ports.length;i++){
            ServerSocketChannel channel = ServerSocketChannel.open();
            channel.configureBlocking(false);
            ServerSocket socket = channel.socket();
            InetSocketAddress address = new InetSocketAddress("localhost",ports[i]);
            socket.bind(address);
            
            //注册接受连接事件
            channel.register(selector, SelectionKey.OP_ACCEPT);
            
            System.out.println( "Going to listen on "+ports[i] ); 
        }
        
        while(true){
            
            int num = selector.select();
            Set<SelectionKey> keys = selector.selectedKeys();
            Iterator<SelectionKey> iter = keys.iterator();
            while(iter.hasNext()){
                SelectionKey key = iter.next();
                if((key.readyOps()&SelectionKey.OP_ACCEPT)==SelectionKey.OP_ACCEPT){
                    ServerSocketChannel  ssc = (ServerSocketChannel) key.channel();
                    SocketChannel sc = ssc.accept();
                    sc.configureBlocking(false);
                    
                    sc.register(selector, SelectionKey.OP_READ);
                    iter.remove();
                }else if((key.readyOps()&SelectionKey.OP_READ)==SelectionKey.OP_READ){
                    
                    SocketChannel sc = (SocketChannel) key.channel();
                    
                    if(!sc.isOpen()){
                        selector = Selector.open();
                    }else{
                        ByteBuffer echoBuffer = ByteBuffer.allocate(1024);  
                        
                        //int x = sc.read(echoBuffer);
                        while(sc.read(echoBuffer)>0){
                            
                            System.out.println( "Echoed "+charset.decode(echoBuffer).toString()+" from "+sc.socket().getInetAddress().getHostAddress() );  
                            echoBuffer.flip();
                            sc.write(echoBuffer);
                            echoBuffer.clear();
                        }
                        
                        
                        iter.remove();
                        
                        /**//*返回信息后关闭连接*/
                        key.cancel();
                        sc.close();
                    }
                }
            }
            
            keys.clear();
        }
    }

}