JAVA NIO 入门

package com.vista.Server;

import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
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.nio.charset.CharsetDecoder;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Set;

public class SelectorServer
{
    private static int DEFAULT_SERVERPORT = 6018;//默认端口
    private static int DEFAULT_BUFFERSIZE = 1024;//默认缓冲区大小为1024字节
    private static String DEFAULT_CHARSET = "GB2312";//默认码集
    private static String DEFAULT_FILENAME = "bigfile.dat";
    private ServerSocketChannel channel;
    private LinkedList<SocketChannel> clients;
    private Selector selector;//选择器
    private ByteBuffer buffer;//字节缓冲区
    private int port;
    private Charset charset;//字符集
    private CharsetDecoder decoder;//解码器
   
   
    public SelectorServer(int port) throws IOException
    {
        this.port = port;
        this.clients = new LinkedList<SocketChannel>();
        this.channel = null;
        this.selector = Selector.open();//打开选择器
        this.buffer = ByteBuffer.allocate(DEFAULT_BUFFERSIZE);
        this.charset = Charset.forName(DEFAULT_CHARSET);
        this.decoder = this.charset.newDecoder();
       
    }
   
     private class HandleClient
     {
         private String strGreeting = "welcome to VistaQQ";
         public HandleClient() throws IOException
         {
         }
         public String readBlock()
         {//读块数据
             return this.strGreeting;
         }
         public void close()
         {
            
         }
    }

    protected void handleKey(SelectionKey key) throws IOException
    {//处理事件
          if (key.isAcceptable())
          { // 接收请求
              ServerSocketChannel server = (ServerSocketChannel) key.channel();//取出对应的服务器通道
              SocketChannel channel = server.accept();
              channel.configureBlocking(false);
              channel.register(selector, SelectionKey.OP_READ);//客户socket通道注册读操作
          }
          else if (key.isReadable())
          { // 读信息
              SocketChannel channel = (SocketChannel) key.channel();
              int count = channel.read(this.buffer);
              if (count > 0)
              {
                this.buffer.flip();
                CharBuffer charBuffer = decoder.decode(this.buffer);
                System.out.println("Client >>" + charBuffer.toString());
                SelectionKey wKey = channel.register(selector,
                    SelectionKey.OP_WRITE);//为客户sockt通道注册写操作
                wKey.attach(new HandleClient());
              }
              else
              {//客户已经断开
                channel.close();
              }
              this.buffer.clear();//清空缓冲区
         }
         else if (key.isWritable())
         { // 写事件
              SocketChannel channel = (SocketChannel) key.channel();
              HandleClient handle = (HandleClient) key.attachment();//取出处理者
              ByteBuffer block = ByteBuffer.wrap(handle.readBlock().getBytes());
              channel.write(block);
             // channel.socket().getInputStream().(block);
//              PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(
//                        channel.socket().getOutputStream())), true);
//              out.write(block.toString());

        }

    }
    public void listen() throws IOException
    { //服务器开始监听端口，提供服务
        ServerSocket socket;
        channel = ServerSocketChannel.open(); // 打开通道
        socket = channel.socket();   //得到与通到相关的socket对象
        socket.bind(new InetSocketAddress(port));   //将scoket榜定在制定的端口上
        //配置通到使用非阻塞模式，在非阻塞模式下，可以编写多道程序同时避免使用复杂的多线程
        channel.configureBlocking(false);   
        channel.register(selector, SelectionKey.OP_ACCEPT);
        try
        {
            while(true)
            {//     与通常的程序不同，这里使用channel.accpet()接受客户端连接请求，而不是在socket对象上调用accept(),这里在调用accept()方法时如果通道配置为非阻塞模式,那么accept()方法立即返回null，并不阻塞
                this.selector.select();
                Iterator iter = this.selector.selectedKeys().iterator();
                while(iter.hasNext())
                {
                    SelectionKey key = (SelectionKey)iter.next();
                    iter.remove();
                    this.handleKey(key);
                   
                }
            }
        }
        catch(IOException ex)
        {
            ex.printStackTrace();
        }
    }
    public static void main(String[] args) throws IOException
    {
        System.out.println("服务器启动");
        SelectorServer server = new SelectorServer(SelectorServer.DEFAULT_SERVERPORT);
        server.listen(); //服务器开始监听端口，提供服务
    }

}