Java nio Socket非阻塞模式

NIO 有一个主要的类Selector,这个类似一个观察者，只要我们把需要探知的socketchannel告诉Selector,我们接着做别的事情，当有 事件发生时，他会通知我们，传回一组SelectionKey,我们读取这些Key,就会获得我们刚刚注册过的socketchannel,然后，我们从 这个Channel中读取数据，放心，包准能够读到，接着我们可以处理这些数据。
Selector内部原理实际是在做一个对所注册的channel的轮询访问，不断的轮询(目前就这一个算法)，一旦轮询到一个channel有所注册的事情发生，比如数据来了，他就会站起来报告，交出一把钥匙，让我们通过这把钥匙来读取这个channel的内容。
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。

server端代码:

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();   
        }   
    }   
}  

client端代码:

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();   
        }   
       
    }   
}