import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.channels.spi.*;
import java.net.*;
import java.util.*;
public class NBTest {
      public NBTest()
      {
      }
      public void startServer() throws Exception
      {
            int channels = 0;
            int nKeys = 0;
            int currentSelector = 0;
            //使用Selector
            Selector selector = Selector.open();
            //建立Channel 并绑定到9000端口
            ServerSocketChannel ssc = ServerSocketChannel.open();
            InetSocketAddress address = new InetSocketAddress(InetAddress.getLocalHost(),9000);
            ssc.socket().bind(address);
            //使设定non-blocking的方式。
            ssc.configureBlocking(false);
            //向Selector注册Channel及我们有兴趣的事件
            SelectionKey s = ssc.register(selector, SelectionKey.OP_ACCEPT);
            printKeyInfo(s);
            while(true) //不断的轮询
            {
                  debug("NBTest: Starting select");
                  //Selector通过select方法通知我们我们感兴趣的事件发生了。
                  nKeys = selector.select();
                  //如果有我们注册的事情发生了，它的传回值就会大于0
                  if(nKeys > 0)
                  {
                        debug("NBTest: Number of keys after select operation: " +nKeys);
                        //Selector传回一组SelectionKeys
                        //我们从这些key中的channel()方法中取得我们刚刚注册的channel。
                        Set selectedKeys = selector.selectedKeys();
                        Iterator i = selectedKeys.iterator();
                        while(i.hasNext())
                        {
                              s = (SelectionKey) i.next();
                              printKeyInfo(s);
                              debug("NBTest: Nr Keys in selector: " +selector.keys().size());
                              //一个key被处理完成后，就都被从就绪关键字（ready keys）列表中除去
                              i.remove();
                              if(s.isAcceptable())
                              {
                                    // 从channel()中取得我们刚刚注册的channel。
                                    Socket socket = ((ServerSocketChannel) s.channel()).accept();
                                    SocketChannel sc = socket.getChannel();
                                    sc.configureBlocking(false);
                                    sc.register(selector, SelectionKey.OP_READ SelectionKey.OP_WRITE);
                                    System.out.println(++channels);
                              }
                              else
                              {
                                    debug("NBTest: Channel not acceptable");
                              }
                        }
                  }
                  else
                  {
                        debug("NBTest: Select finished without any keys.");
                  }
            }
      }
      private static void debug(String s)
      {
            System.out.println(s);
      }
      private static void printKeyInfo(SelectionKey sk)
      {
            String s = new String();
            s = "Att: " + (sk.attachment() == null ? "no" : "yes");
            s += ", Read: " + sk.isReadable();
            s += ", Acpt: " + sk.isAcceptable();
            s += ", Cnct: " + sk.isConnectable();
            s += ", Wrt: " + sk.isWritable();
            s += ", Valid: " + sk.isValid();
            s += ", Ops: " + sk.interestOps();
            debug(s);
      }
      public static void main (String args[])
      {
            NBTest nbTest = new NBTest();
            try
            {
                  nbTest.startServer();
            }
            catch(Exception e)
            {
                  e.printStackTrace();
            }
      }
}