NIO demo

使用NIO编程的优点:

1.客户端发起的连接操作是异步的，可以通过在多路复用器注册OP_CONNECT等待后续结果，不需要像之前的客户端那样被同步阻塞.

2.SocketChannel的读写操作都是异步的，如果没有可读写的数据它不会同步等待，直接返回，这样I/O通信线程就可以处理其他的链路，不需要同步等待这个链路可用。

３．线程模型的优化：由于ＪＤＫ的Ｓｅｌｅｃｔｏｒ在Ｌｉｎｕｘ等主流操作系统上通过ｅｐｏｌｌ实现，它没有连接句柄数的限制（只受限于操作系统的最大句柄数或者单个进程的句柄限制），这意味着一个Ｓｅｌｅｃｔｏｒ线程可以同时处理成千上万个客户端连接，而且性能不会随着客户端的增加而线性下降。因此，它非常适合做高性能、高负载的网络服务器。

Server:

package netty.chapter2;

public class TimeServer {

    public static void main(String[] args) {
        int port = 8090;
        MultiplexerTimeServer timeServer = new MultiplexerTimeServer(port);
        new Thread(timeServer,"NIO-MultiplexerTimeServer-001").start();
    }

}

package netty.chapter2;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Date;
import java.util.Iterator;
import java.util.Set;

public class MultiplexerTimeServer implements Runnable{
    
    private Selector selector;
    
    private ServerSocketChannel servChannel;
    
    private volatile boolean stop;
    
    /**
     * @Description 初始化多路复用器，绑定监听端口
     */
    public MultiplexerTimeServer(int port) {
        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.
            servChannel = ServerSocketChannel.open();
            //2.绑定监听端口，设置连接为非阻塞模式
            servChannel.socket().bind(new InetSocketAddress(port), 1024);
            servChannel.configureBlocking(false);
            //3.创建多路复用器
            selector = Selector.open();
            //4.将ServerSocketChannel注册到多路复用器Selector上，监听ACCEPT事件
            servChannel.register(selector, SelectionKey.OP_ACCEPT);
            System.out.println("The time server is started in port:"+port);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }
    
    public void stop(){
        this.stop = true;
    }

    public void run() {
        while(!stop){
            try {
                //5.轮询准备就绪的Key
                selector.select(1000);
                Set<SelectionKey> selectedKeys = selector.selectedKeys();
                Iterator<SelectionKey> it = selectedKeys.iterator();
                SelectionKey key = null;
                while(it.hasNext()){
                    key = it.next();
                    it.remove();
                    try {
                        handleInput(key);
                    } catch (Exception e) {
                        if(key != null){
                            key.cancel();
                            if(key.channel() != null)
                                key.channel().close();
                        }
                    }
                    
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        
    }
    
    private void handleInput(SelectionKey key) throws IOException{
        if(key.isValid()){
            //处理新接入的请求消息
            if(key.isAcceptable()){
                //6.处理新的接入请求
                ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
                SocketChannel sc = ssc.accept();
                //7.设置客户端链路为非阻塞模式
                sc.configureBlocking(false);
                //8.将新接入的客户端连接注册到多路复用器上，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()){
                SocketChannel sc = (SocketChannel)key.channel();
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                //9.异步读取客户端请求消息到缓冲区
                int readBytes = sc.read(readBuffer);
                if(readBytes >0){
                    readBuffer.flip();
                    byte[] bytes = new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes,"UTF-8");
                    System.out.println("The time server receive order:"+body);
                    String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(System.currentTimeMillis()).toString() : "BAD ORDER";
                    doWrite(sc, currentTime);
                }else if(readBytes <0){
                    key.cancel();
                    sc.close();
                }else{
                    System.out.println("0 size bytes");
                }
            }
        }
    }
    
    private void doWrite(SocketChannel channel,String response) throws IOException{
        //10.将消息异步发送给客户端
        if(response !=null && response.trim().length()>0){
            byte[] bytes = response.getBytes();
            ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
            writeBuffer.put(bytes);
            writeBuffer.flip();
            channel.write(writeBuffer);
        }
    }

}

Client:

package netty.chapter2;

public class TimeClient {

    public static void main(String[] args) {
        int port = 8090;
        new Thread(new TimeClinetHandle("127.0.0.1", port), "TimeClient-001").start();
    }

}

package netty.chapter2;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class TimeClinetHandle implements Runnable {

    private String host;
    private int port;
    private Selector selector;
    private SocketChannel socketChannel;
    private volatile boolean stop;

    public TimeClinetHandle(String host, int port) {
        this.host = host == null ? "127.0.0.1" : host;
        this.port = port;
        try {
            //1.打开SocketChannel
            socketChannel = SocketChannel.open();
            //2.设置SocketChannel为非阻塞模式
            socketChannel.configureBlocking(false);
            //4.创建多路复用器
            selector = Selector.open();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public void run() {
        try {
            doConnect();
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
        while (!stop) {
            try {
                //5.轮询准备就绪的key
                selector.select(1000);
                Set<SelectionKey> selectedKeys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = selectedKeys.iterator();
                SelectionKey key = null;
                while (iterator.hasNext()) {
                    key = iterator.next();
                    iterator.remove();
                    try {
                        handleInput(key);
                    } catch (Exception e) {
                        if (key != null) {
                            key.cancel();
                            if (key.channel() != null)
                                key.channel().close();
                        }
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
                System.exit(1);
            }
        }
        //多路复用器关闭后，所有注册在上面的Channel和Pipe等资源都会被自动去注册并关闭，所以不需要重复释放资源
        if (selector != null) {
            try {
                selector.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    private void handleInput(SelectionKey key) throws IOException {
        if (key.isValid()) {
            SocketChannel sc = (SocketChannel) key.channel();
            //6.接收connect事件进行处理
            if (key.isConnectable()) {
                //7.连接成功，注册读事件到多路复用器
                if (sc.finishConnect()) {
                    sc.register(selector, SelectionKey.OP_READ);
                    doWrite(sc);
                } else {
                    System.exit(1);
                }
            }
            //8.异步读服务器返回消息到缓冲区
            if (key.isReadable()) {
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                int readBytes = sc.read(readBuffer);
                if (readBytes > 0) {
                    readBuffer.flip();
                    byte[] bytes = new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes, "UTF-8");
                    System.out.println("Now is:" + body);
                    this.stop = true;
                } else if (readBytes < 0) {
                    key.cancel();
                    sc.close();
                } else {
                    System.out.println("0 size bytes.");
                }
            }
        }
    }

    private void doConnect() throws IOException {
        //3.异步连接服务器
        //成功，注册
        if (socketChannel.connect(new InetSocketAddress(host, port))) {
            socketChannel.register(selector, SelectionKey.OP_READ);
            doWrite(socketChannel);
        } else {//注册，监听服务器的ack
            socketChannel.register(selector, SelectionKey.OP_CONNECT);
        }
    }

    private void doWrite(SocketChannel sc) throws IOException {
        //9.调用SocketChannel的异步write接口，将消息异步发送给服务器
        byte[] req = "QUERY TIME ORDER".getBytes();
        ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
        writeBuffer.put(req);
        writeBuffer.flip();
        sc.write(writeBuffer);
        if (!writeBuffer.hasRemaining()) {
            System.out.println("Send order 2 server succeed.");
        }
    }

}