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

new Thread(new ReactorTask()).start();

}

public static class ReactorTask implements Runnable{

private Selector selector;

public ReactorTask() {

try{

//1.打开ServerSocketChannel，用于监听客户端的连接，它是所有客户端连接的父管道

ServerSocketChannel acceptorSvr = ServerSocketChannel.open();

//2.绑定监听端口

acceptorSvr.socket().bind(new InetSocketAddress(InetAddress.getByName("localhost"), 9999));

//3.设置连接为非阻塞模式

acceptorSvr.configureBlocking(false);

//4.创建Reactor线程，创建多路复用器并启动线程

selector = Selector.open();

//5.将ServerSocketChannel注册到Reactor线程的多路复用器Selector上，监听Accept事件

SelectionKey key = acceptorSvr.register(selector, SelectionKey.OP_ACCEPT);

} catch (UnknownHostException e){

e.printStackTrace();

} catch (IOException e){

e.printStackTrace();

}

}//ReactorTask

@Override

public void run() {

//6.在run方法中的无限循环体内，轮询准备就绪的Key

while (true){

try{

selector.select(1000);

Set selectedKeys = selector.selectedKeys();

Iterator it = selectedKeys.iterator();

SelectionKey key = null;

while (it.hasNext()){

key = (SelectionKey) it.next();

it.remove();

try{

if (key.isValid()){

//处理新接入的请求消息

if(key.isAcceptable()){

//7.多路复用器监听到有新的客户端接入，处理新的接入请求，完成TCP三次握手，建立物理链路

ServerSocketChannel ssc = (ServerSocketChannel) key.channel();

SocketChannel sc = ssc.accept();

//8.设置客户端链路为非阻塞模式

sc.configureBlocking(false);

sc.socket().setReuseAddress(true);

//9.将新接入的客户端连接注册到Reactor线程的多路复用器上，监听读操作，读取客户端发送的网络消息

sc.register(selector, SelectionKey.OP_READ);

}

if(key.isReadable()){

//10.异步读取客户端请求消息到缓存区

SocketChannel sc = (SocketChannel) key.channel();

ByteBuffer readBuffer = ByteBuffer.allocate(64*1024);

int readBytes = sc.read(readBuffer);

//11.对ByteBuffer进行编解码，如果有半包消息指针reset，继续读取后续的报文

if(readBytes > 0){

readBuffer.flip();

byte[] bytes = new byte[readBuffer.remaining()];

readBuffer.get(bytes);

String body = new String(bytes, "UTF-8");

System.out.println("Server receive a order: \"" + body + "\"");

readBuffer.clear();

String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(System.currentTimeMillis()).toString() : "OTHER ORDER";

//写应答

byte[] bytes2 = ("CurrentTime is: " + currentTime).getBytes();

ByteBuffer writeBuffer = ByteBuffer.allocate(bytes2.length);

writeBuffer.put(bytes2);

writeBuffer.flip();

sc.write(writeBuffer);

} else if(readBytes < 0) {

//对端链路关闭

key.cancel();

sc.close();

}else ;// 读到0字节，忽略

}

}

}catch (Exception e){

if(key != null){

key.cancel();

if(key.channel() != null)

key.channel().close();

}

}

}//while

}catch (Throwable t){

t.printStackTrace();

}

}//while

}//run

}