import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.channels.spi.*;
import java.net.*;
import java.util.*;
import java.nio.charset.*;

/**
 * Description:
 * <br/>Copyright (C), 2008-2010, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee kongyeeku@163.com
 * @version  1.0
 */
public class NServer
{
	//用于檢測所有Channel狀態的Selector
	private Selector selector = null;
	//定義實現編碼、解碼的字符集對象
	private Charset charset = Charset.forName("UTF-8");
    public void init()throws IOException
    {
		selector = Selector.open();
		//通過open方法來打開一個未綁定的ServerSocketChannel實例
		ServerSocketChannel server = ServerSocketChannel.open();
		InetSocketAddress isa = new InetSocketAddress(
			"127.0.0.1", 30000); 
		//將該ServerSocketChannel綁定到指定IP地址
		server.socket().bind(isa);
		//設置ServerSocket以非阻塞方式工作
		server.configureBlocking(false);
		//將server注冊到指定Selector對象
		server.register(selector, SelectionKey.OP_ACCEPT);
		while (selector.select() > 0) 
		{
			//依次處理selector上的每個已選擇的SelectionKey
			for (SelectionKey sk : selector.selectedKeys())
			{
				//從selector上的已選擇Key集中刪除正在處理的SelectionKey
				selector.selectedKeys().remove(sk);
				//如果sk對應的通道包含客戶端的連接請求
				if (sk.isAcceptable())
				{
					//調用accept方法接受連接，產生服務器端對應的SocketChannel
					SocketChannel sc = server.accept();
					//設置采用非阻塞模式
					sc.configureBlocking(false);
					//將該SocketChannel也注冊到selector
					sc.register(selector, SelectionKey.OP_READ);
					//將sk對應的Channel設置成準備接受其他請求
					sk.interestOps(SelectionKey.OP_ACCEPT);
				}
				//如果sk對應的通道有數據需要讀取
				if (sk.isReadable())
				{
					//獲取該SelectionKey對應的Channel，該Channel中有可讀的數據
					SocketChannel sc = (SocketChannel)sk.channel();
					//定義準備執行讀取數據的ByteBuffer
					ByteBuffer buff = ByteBuffer.allocate(1024);
					String content = "";
					//開始讀取數據
					try
					{
						while(sc.read(buff) > 0)
						{
							buff.flip();
							content += charset.decode(buff);
						}
						//打印從該sk對應的Channel里讀取到的數據
						System.out.println("=====" + content);
						//將sk對應的Channel設置成準備下一次讀取
						sk.interestOps(SelectionKey.OP_READ);
					}
					//如果捕捉到該sk對應的Channel出現了異常，即表明該Channel
					//對應的Client出現了問題，所以從Selector中取消sk的注冊
					catch (IOException ex)
					{
						//從Selector中刪除指定的SelectionKey
						sk.cancel();
						if (sk.channel() != null)
						{
							sk.channel().close();
						}
					}
					//如果content的長度大于0，即聊天信息不為空
					if (content.length() > 0)
					{
						//遍歷該selector里注冊的所有SelectKey
						for (SelectionKey key : selector.keys())
						{
							//獲取該key對應的Channel
							Channel targetChannel = key.channel();
							//如果該channel是SocketChannel對象
							if (targetChannel instanceof SocketChannel)
							{
								//將讀到的內容寫入該Channel中
								SocketChannel dest = (SocketChannel)targetChannel;
								dest.write(charset.encode(content));
							}
						}
					}
				}
			}
		}
    }
	
	public static void main(String[] args)
		throws IOException
	{
		new NServer().init();
	}
}