public abstract class SelectionKey {
    public static final int OP_READ
    public static final int OP_WRITE
    public static final int OP_CONNECT
    public static final int OP_ACCEPT
    public abstract SelectableChannel channel();
    public abstract Selector selector();
    public abstract void cancel();
    public abstract boolean isValid();
    public abstract int interestOps();
    public abstract void interestOps(int ops);
    public abstract int readyOps();
    public final boolean isReadable()
    public final boolean isWritable()
    public final boolean isConnectable()
    public final boolean isAcceptable()
    public final Object attach(Object ob)
    public final Object attachment()
}

channel.register(this.selector, SelectionKey.OP_READ);

public abstract class AbstractNioServer {
    protected final static String CHARSET = "utf-8";
 protected String ip;
 protected Integer port;
 protected Selector selector;
 public AbstractNioServer(String ip, Integer port) {
        this.ip = ip;
 this.port = port;
 }
    /**
 * 客戶端連接請(qǐng)求
 *
 * @param key
 */
 protected abstract void accept(SelectionKey key) throws IOException;
 /**
 * 讀取數(shù)據(jù)
 *
 * @param key
 */
 protected abstract void read(SelectionKey key) throws IOException;
 /**
 * 初始化服務(wù)器
 *
 * @throws IOException
 */ public void init() throws IOException {
        //設(shè)置服務(wù)器地址端口
 SocketAddress address = new InetSocketAddress(this.ip, this.port);
 //創(chuàng)建服務(wù)端通道
 ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
 //綁定服務(wù)器地址
 serverSocketChannel.bind(address);
 //設(shè)置為非阻塞模式
 serverSocketChannel.configureBlocking(false);
 //創(chuàng)建一個(gè)選擇器
 this.selector = Selector.open();
 //將服務(wù)器通道注冊(cè)到選擇器中，ServerSocketChannel只支持accept事件注冊(cè)，validOps返回16
 serverSocketChannel.register(this.selector, SelectionKey.OP_ACCEPT);
 }
    public void start() throws IOException {
        this.init();
 while (true) {
            int count = this.selector.select();
 if (count == 0) {
                //沒(méi)有就緒的選擇鍵
 continue;
 }
            Iterator<SelectionKey> iterator = this.selector.selectedKeys().iterator();
 while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
 if (!key.isValid()) {
                    continue;
 }
                if (key.isAcceptable()) {
                    //連接請(qǐng)求
 accept(key);
 } else if (key.isReadable()) {
                    //修改鍵的感興趣事件，防止被 select 重復(fù)調(diào)用，處理完事件后及時(shí)恢復(fù)
 key.interestOps(key.interestOps() & (~SelectionKey.OP_READ));
 //讀取消息
 read(key);
 }
                iterator.remove();
 }
        }
    }
    /**
 * 恢復(fù)鍵的感興趣事件
 * @param key
 */
 protected void resumeInterOpsRead(SelectionKey key) {
        //還原key的感興趣事件
 key.interestOps(key.interestOps() | SelectionKey.OP_READ);
 //喚醒selector的select事件
 key.selector().wakeup();
 }
}

public class SingleNioServer extends AbstractNioServer {
    public static void main(String[] args) {
        SingleNioServer server = new SingleNioServer("127.0.0.1", 1008);
 try {
            server.start();
 } catch (IOException e) {
            e.printStackTrace();
 }
    }
    public SingleNioServer(String ip, Integer port) {
        super(ip, port);
 }
    @Override
 protected void accept(SelectionKey key) throws IOException {
        ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
 //SocketChannel支持 read、write、connect 事件注冊(cè)，validOps返回13=1+4+8
 SocketChannel channel = serverChannel.accept();
 if (channel == null) {
            return;
 }
        System.out.println("新的連接請(qǐng)求");
 channel.configureBlocking(false);
 //如果是阻塞通道進(jìn)行注冊(cè)，會(huì)拋出 IllegalBlockingModeException 異常
 channel.register(this.selector, SelectionKey.OP_READ);
 }
    @Override
 protected void read(SelectionKey key) throws IOException {
        SocketChannel channel = (SocketChannel) key.channel();
 try {
            ByteBuffer buffer = ByteBuffer.allocate(1024);
 int len = channel.read(buffer);
 buffer.flip();
 if (len > 0) {
                String str = Charset.forName(CHARSET).decode(buffer).toString();
 System.out.println("客戶端消息：" + str);
 String msg = "消息已收到";
 byte[] sendData = msg.getBytes(CHARSET);
 ByteBuffer sendBuffer = ByteBuffer.wrap(sendData);
 channel.write(sendBuffer);
 super.resumeInterOpsRead(key);
 } else if (len == -1) {
                System.out.println("socket client close");
 key.cancel();
 channel.close();
 }
        } catch (IOException ex) {
            key.cancel();
 channel.close();
 }
    }
}

public class MulitpleNioServer extends AbstractNioServer {
    public static void main(String[] args) throws IOException {
        MulitpleNioServer server = new MulitpleNioServer("127.0.0.1", 1008);
 server.start();
 }
    /**
 * 線程池
 */
 private ExecutorService executorService = Executors.newFixedThreadPool(5);
 public MulitpleNioServer(String ip, Integer port) {
        super(ip, port);
 }
    @Override
 protected void accept(SelectionKey key) throws IOException {
        ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
 //SocketChannel支持 read、write、connect 事件注冊(cè)，validOps返回13=1+4+8
 SocketChannel channel = serverChannel.accept();
 System.out.println("新的連接請(qǐng)求");
 channel.configureBlocking(false);
 channel.register(this.selector, SelectionKey.OP_READ);
 }
    @Override
 protected void read(SelectionKey key) throws IOException {
        executorService.submit(new Runnable() {
            @Override
 public void run() {
                readData(key);
 }
        });
 }
    private void readData(SelectionKey key) {
        SocketChannel channel = (SocketChannel) key.channel();
 try {
            ByteBuffer buffer = ByteBuffer.allocate(1024);
 if (channel.isOpen()) {
                if (channel.isConnected()) {
                    int len = channel.read(buffer);
 buffer.flip();
 if (len > 0) {
                        String str = Charset.forName(CHARSET).decode(buffer).toString();
 System.out.println("客戶端消息：" + str);
 String msg = "消息已收到";
 byte[] sendData = msg.getBytes(CHARSET);
 ByteBuffer sendBuffer = ByteBuffer.wrap(sendData);
 channel.write(sendBuffer);
 } else if (len == -1) {
                        System.out.println("socket client close1");
 key.cancel();
 channel.close();
 }
                    super.resumeInterOpsRead(key);
 }
            }
        } catch (IOException ex) {
            System.out.println("client is close2");
 key.cancel();
 try {
                channel.close();
 } catch (IOException e) {
                e.printStackTrace();
 }
        }
    }
}