jdk供的无阻塞I/O

 jdk供的无阻塞I/O（NIO）有效解决了多线程服务器存在的线程开销问题，但在使用上略显得复杂一些。在NIO中使用多线程，主要目的已不是为了应对每个客户端请求而分配独立的服务线程，而是通过多线程充分使用用多个CPU的处理能力和处理中的等待时间，达到提高服务能力的目的。
    这段时间在研究NIO，写篇博客来记住学过的东西。还是从最简单的Hello World开始，
client多线程请求server端，server接收client的名字，并返回Hello! ＋名字的字符格式给client。当然实际应用并不这么简单，实际可能是访问文件或者数据库获取信息返回给client。非阻塞的NIO有何神秘之处？代码：

1)server端代码

Java代码
/**
*   
* @author Jeff
*
*/
public class HelloWorldServer {   

    static int BLOCK = 1024;   
    static String name = "";   
    protected Selector selector;   
    protected ByteBuffer clientBuffer = ByteBuffer.allocate(BLOCK);   
    protected CharsetDecoder decoder;   
    static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();   

    public HelloWorldServer(int port) throws IOException {   
        selector = this.getSelector(port);   
        Charset charset = Charset.forName("GB2312");   
        decoder = charset.newDecoder();   
    }   

    // 获取Selector   
    protected Selector getSelector(int port) throws IOException {   
        ServerSocketChannel server = ServerSocketChannel.open();   
        Selector sel = Selector.open();   
        server.socket().bind(new InetSocketAddress(port));   
        server.configureBlocking(false);   
        server.register(sel, SelectionKey.OP_ACCEPT);   
        return sel;   
    }   

    // 监听端口   
    public void listen() {   
        try {   
            for (;;) {   
                selector.select();   
                Iterator iter = selector.selectedKeys().iterator();   
                while (iter.hasNext()) {   
                    SelectionKey key = (SelectionKey) iter.next();   
                    iter.remove();   
                    process(key);   
                }   
            }   
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
    }   

    // 处理事件   
    protected void process(SelectionKey key) throws IOException {   
        if (key.isAcceptable()) { // 接收请求   
            ServerSocketChannel server = (ServerSocketChannel) key.channel();   
            SocketChannel channel = server.accept();   
            //设置非阻塞模式   
            channel.configureBlocking(false);   
            channel.register(selector, SelectionKey.OP_READ);   
        } else if (key.isReadable()) { // 读信息   
            SocketChannel channel = (SocketChannel) key.channel();   
            int count = channel.read(clientBuffer);   
            if (count > 0) {   
                clientBuffer.flip();   
                CharBuffer charBuffer = decoder.decode(clientBuffer);   
                name = charBuffer.toString();   
                // System.out.println(name);   
                SelectionKey sKey = channel.register(selector,   
                        SelectionKey.OP_WRITE);   
                sKey.attach(name);   
            } else {   
                channel.close();   
            }   

            clientBuffer.clear();   
        } else if (key.isWritable()) { // 写事件   
            SocketChannel channel = (SocketChannel) key.channel();   
            String name = (String) key.attachment();   
               
            ByteBuffer block = encoder.encode(CharBuffer   
                    .wrap("Hello !" + name));   
               

            channel.write(block);   

            //channel.close();   

        }   
    }   

    public static void main(String[] args) {   
        int port = 8888;   
        try {   
            HelloWorldServer server = new HelloWorldServer(port);   
            System.out.println("listening on " + port);   
               
            server.listen();   
               
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
    }   
}
/**
*
* @author Jeff
*
*/
public class HelloWorldServer {

static int BLOCK = 1024;
static String name = "";
protected Selector selector;
protected ByteBuffer clientBuffer = ByteBuffer.allocate(BLOCK);
protected CharsetDecoder decoder;
static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();

public HelloWorldServer(int port) throws IOException {
   selector = this.getSelector(port);
   Charset charset = Charset.forName("GB2312");
   decoder = charset.newDecoder();
}

// 获取Selector
protected Selector getSelector(int port) throws IOException {
   ServerSocketChannel server = ServerSocketChannel.open();
   Selector sel = Selector.open();
   server.socket().bind(new InetSocketAddress(port));
   server.configureBlocking(false);
   server.register(sel, SelectionKey.OP_ACCEPT);
   return sel;
}

// 监听端口
public void listen() {
   try {
    for (;;) {
     selector.select();
     Iterator iter = selector.selectedKeys().iterator();
     while (iter.hasNext()) {
      SelectionKey key = (SelectionKey) iter.next();
      iter.remove();
      process(key);
     }
    }
   } catch (IOException e) {
    e.printStackTrace();
   }
}

// 处理事件
protected void process(SelectionKey key) throws IOException {
   if (key.isAcceptable()) { // 接收请求
    ServerSocketChannel server = (ServerSocketChannel) key.channel();
    SocketChannel channel = server.accept();
    //设置非阻塞模式
    channel.configureBlocking(false);
    channel.register(selector, SelectionKey.OP_READ);
   } else if (key.isReadable()) { // 读信息
    SocketChannel channel = (SocketChannel) key.channel();
    int count = channel.read(clientBuffer);
    if (count > 0) {
     clientBuffer.flip();
     CharBuffer charBuffer = decoder.decode(clientBuffer);
     name = charBuffer.toString();
     // System.out.println(name);
     SelectionKey sKey = channel.register(selector,
       SelectionKey.OP_WRITE);
     sKey.attach(name);
    } else {
     channel.close();
    }

    clientBuffer.clear();
   } else if (key.isWritable()) { // 写事件
    SocketChannel channel = (SocketChannel) key.channel();
    String name = (String) key.attachment();
   
    ByteBuffer block = encoder.encode(CharBuffer
      .wrap("Hello !" + name));
   

    channel.write(block);

    //channel.close();

   }
}

public static void main(String[] args) {
   int port = 8888;
   try {
    HelloWorldServer server = new HelloWorldServer(port);
    System.out.println("listening on " + port);
   
    server.listen();
   
   } catch (IOException e) {
    e.printStackTrace();
   }
}
}


server主要是读取client发过来的信息，并返回一条信息

2)client端代码

Java代码

/**
*   
* @author Jeff
*
*/
public class HelloWorldClient {   

    static int SIZE = 10;   
    static InetSocketAddress ip = new InetSocketAddress("localhost", 8888);   
    static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();   

    static class Message implements Runnable {   
        protected String name;   
        String msg = "";   

        public Message(String index) {   
            this.name = index;   
        }   

        public void run() {   
            try {   
                long start = System.currentTimeMillis();   
                //打开Socket通道   
                SocketChannel client = SocketChannel.open();   
                //设置为非阻塞模式   
                client.configureBlocking(false);   
                //打开选择器   
                Selector selector = Selector.open();   
                //注册连接服务端socket动作   
                client.register(selector, SelectionKey.OP_CONNECT);   
                //连接   
                client.connect(ip);   
                //分配内存   
                ByteBuffer buffer = ByteBuffer.allocate(8 * 1024);   
                int total = 0;   

                _FOR: for (;;) {   
                    selector.select();   
                    Iterator iter = selector.selectedKeys().iterator();   

                    while (iter.hasNext()) {   
                        SelectionKey key = (SelectionKey) iter.next();   
                        iter.remove();   
                        if (key.isConnectable()) {   
                            SocketChannel channel = (SocketChannel) key   
                                    .channel();   
                            if (channel.isConnectionPending())   
                                channel.finishConnect();   
                            channel   
                                    .write(encoder   
                                            .encode(CharBuffer.wrap(name)));   

                            channel.register(selector, SelectionKey.OP_READ);   
                        } else if (key.isReadable()) {   
                            SocketChannel channel = (SocketChannel) key   
                                    .channel();   
                            int count = channel.read(buffer);   
                            if (count > 0) {   
                                total += count;   
                                buffer.flip();   

                                while (buffer.remaining() > 0) {   
                                    byte b = buffer.get();   
                                    msg += (char) b;   
                                       
                                }   

                                buffer.clear();   
                            } else {   
                                client.close();   
                                break _FOR;   
                            }   
                        }   
                    }   
                }   
                double last = (System.currentTimeMillis() - start) * 1.0 / 1000;   
                System.out.println(msg + "used time :" + last + "s.");   
                msg = "";   
            } catch (IOException e) {   
                e.printStackTrace();   
            }   
        }   
    }   

    public static void main(String[] args) throws IOException {   
       
        String names[] = new String[SIZE];   

        for (int index = 0; index < SIZE; index++) {   
            names[index] = "jeff[" + index + "]";   
            new Thread(new Message(names[index])).start();   
        }   
       
    }   
}
/**
*
* @author Jeff
*
*/
public class HelloWorldClient {

static int SIZE = 10;
static InetSocketAddress ip = new InetSocketAddress("localhost", 8888);
static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();

static class Message implements Runnable {
   protected String name;
   String msg = "";

   public Message(String index) {
    this.name = index;
   }

   public void run() {
    try {
     long start = System.currentTimeMillis();
     //打开Socket通道
     SocketChannel client = SocketChannel.open();
     //设置为非阻塞模式
     client.configureBlocking(false);
     //打开选择器
     Selector selector = Selector.open();
     //注册连接服务端socket动作
     client.register(selector, SelectionKey.OP_CONNECT);
     //连接
     client.connect(ip);
     //分配内存
     ByteBuffer buffer = ByteBuffer.allocate(8 * 1024);
     int total = 0;

     _FOR: for (;;) {
      selector.select();
      Iterator iter = selector.selectedKeys().iterator();

      while (iter.hasNext()) {
       SelectionKey key = (SelectionKey) iter.next();
       iter.remove();
       if (key.isConnectable()) {
        SocketChannel channel = (SocketChannel) key
          .channel();
        if (channel.isConnectionPending())
         channel.finishConnect();
        channel
          .write(encoder
            .encode(CharBuffer.wrap(name)));

        channel.register(selector, SelectionKey.OP_READ);
       } else if (key.isReadable()) {
        SocketChannel channel = (SocketChannel) key
          .channel();
        int count = channel.read(buffer);
        if (count > 0) {
         total += count;
         buffer.flip();

         while (buffer.remaining() > 0) {
          byte b = buffer.get();
          msg += (char) b;
         
         }

         buffer.clear();
        } else {
         client.close();
         break _FOR;
        }
       }
      }
     }
     double last = (System.currentTimeMillis() - start) * 1.0 / 1000;
     System.out.println(msg + "used time :" + last + "s.");
     msg = "";
    } catch (IOException e) {
     e.printStackTrace();
    }
   }
}

public static void main(String[] args) throws IOException {

   String names[] = new String[SIZE];

   for (int index = 0; index < SIZE; index++) {
    names[index] = "jeff[" + index + "]";
    new Thread(new Message(names[index])).start();
   }

}
}