NIO编程

Posted junjiang3

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相关概念

  • 缓冲区Buffer
    Buffer是一个对象,它包含一些要写入或者要读出的数据。在NIO库中,所有数据都是用缓冲区处理的。缓冲区实质上是一个数组,最常用的缓冲区是ByteBuffer。

  • 通道 Channel
    通道像一个自来水管一样,网络数据通过Channel读取和写入。其和流的区别是,流只能在一个方向上移动,而通道可以用于读、写或者二者同时进行。

  • 多路复用器 Selector
    多路复用器提供选择就绪的任务的能力。简单来说Selector会不断的轮询注册在其上的Channel。

NIO服务端时序图

技术分享图片

  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通道。
  2. 绑定监听的端口,设置为非阻塞模式
  3. 创建Reactor线程,创建多路复用器并启动线程
  4. 将ServerSocketChannel注册到Reactor线程的多路复用器Selector上,监听ACCEPT事件
  5. 多路复用器在线程run方法的无限循环体内轮询准备就绪的Key
  6. 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。
  7. 设置客户端链路为非阻塞模式。
  8. 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。
  9. 异步读取客户端请求消息到缓冲区
  10. 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,将解码成功的消息封装成Task,投递到业务线程池中,进行业务逻辑编排。
  11. 将POJO对象encode成ByteBuffer,调用SocketChannel异步写入接口,将消息异步发送给客户端。

NIO改造后的TimeServer

public class TimeServer {

    public static void main(String[] args) throws IOException {
        int port  = 8080;
        if (args != null && args.length >0){
            try{
                port = Integer.parseInt(args[0]);
            }catch (NumberFormatException e){

            }
        }

        MultiplexerTimeServer timeServer = new MultiplexerTimeServer(port);

        new Thread(timeServer).start();
    }
}

其中,我们创建了一个MultiplexerTimeServer的多路复用类,它是一个独立的线程,负责轮询多路复用器Selector,其代码如下:

public class MultiplexerTimeServer implements Runnable{

    private Selector selector;

    private ServerSocketChannel serverSocketChannel;

    private volatile boolean stop;

    public MultiplexerTimeServer(int port){
        try {
            selector = Selector.open();
            serverSocketChannel =  ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.socket().bind(new InetSocketAddress(port),1024);
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public void stop(){
        this.stop = true;
    }

    public void run() {
        while (!stop){
            try{
                selector.select(1000);
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = selectionKeys.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 (Throwable e) {
                e.printStackTrace();
            }
        }
    }

    private void handleInput(SelectionKey key) throws IOException {
        if (key.isValid()){
            if (key.isAcceptable()){
                ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
                SocketChannel sc = ssc.accept();
                sc.configureBlocking(false);
                sc.register(selector,SelectionKey.OP_READ);
            }
            if (key.isReadable()){
                SocketChannel sc = (SocketChannel)key.channel();
                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");
                    String curentTime = "QUERY TIME ORDER".equalsIgnoreCase(body)?new Date(
                            System.currentTimeMillis()
                    ).toString():"BAD ORDER";
                    doWrite(sc,curentTime);
                }else if(readBytes<0){
                    key.cancel();
                    sc.close();
                }else{

                }
            }
        }
    }

    private void doWrite(SocketChannel channel,String response) throws IOException {
        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);
        }
    }
}

NIO客户端时序图

技术分享图片

  1. 打开SocketChannel,绑定客户端本地地址
  2. 设置SocketChannel为非阻塞模式,同时设置客户端连接的TCP参数
  3. 异步连接服务端
  4. 判断是否连接成功,如果连接成功,则直接注册读状态未到多路复用器中。
  5. 向Reactor线程的多路复用器注册OP_CONNECT状态位,监听服务端的TCP ACK应答。
  6. 创建Reactor线程,创建多路复用器启动线程
  7. 多路复用器在线程run方法的无限循环体中轮询准备就绪的Key
  8. 接受connect事件进行处理
  9. 判断连接成功,如果连接成功,注册读事件到多路复用器
  10. 注册读事件到多路复用器
  11. 异步读客户端请求到缓冲区
  12. 对ByteBuffer进行编解码,如果有半包消息接受缓冲区Reset,继续读取后续的报文,将解码成功的消息封装成Task,投递到业务线程池中,进行业务逻辑编排。

NIO改造后 TimeClient

public class TimeClient {

    public static void main(String[] args) throws IOException {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.parseInt(args[0]);
            } catch (NumberFormatException e) {

            }
        }
        new Thread(new TimeClientHandle("127.0.0.1",port)).start();
    }
}

与之前不同的地方在于通过创建TimeClientHandle线程来处理异步连接和读写操作 ,因此下面我们看看TimeClientHandle的实现。

public class TimeClientHandle implements Runnable{
    private String host;
    private int port;
    private Selector selector;
    private SocketChannel socketChannel;
    private volatile boolean stop;

    public TimeClientHandle(String host, int port) {
        this.host = host == null ? "127.0.0.1":host;
        this.port = port;
        try {
            selector = Selector.open();
            socketChannel = SocketChannel.open();
            socketChannel.configureBlocking(false);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public void run() {
        try {
            doConnect();
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
        while (!stop){
            try{
                selector.select(1000);
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> it = selectionKeys.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 (IOException e) {
                e.printStackTrace();
                System.exit(1);
            }
        }
    }

    private void handleInput(SelectionKey key) throws IOException {
        if (key.isValid()){
            SocketChannel sc = (SocketChannel) key.channel();
            if (key.isConnectable()){
                if (sc.finishConnect()){
                    sc.register(selector,SelectionKey.OP_READ);
                    doWrite(sc);
                }else{
                    System.exit(1);
                }
            }
            if (key.isReadable()){
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                int readBytes = sc.read(readBuffer);
                if (readBytes > 0){
                    byte[] bytes = new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes,"UTF-8");
                    System.out.println(body);
                    this.stop = true;
                }else if(readBytes < 0){
                    key.cancel();
                    sc.close();
                }else{

                }
            }
        }
    }

    private void doConnect() throws IOException {
        if (socketChannel.connect(new InetSocketAddress(host,port))){
            socketChannel.register(selector, SelectionKey.OP_READ);
            doWrite(socketChannel);
        }else{
            socketChannel.register(selector,SelectionKey.OP_CONNECT);
        }
    }

    private void doWrite(SocketChannel sc) throws IOException {
        byte[] bytes = "QUERY TIME ORDER".getBytes();
        ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
        writeBuffer.put(bytes);
        writeBuffer.flip();
        sc.write(writeBuffer);
        if (!writeBuffer.hasRemaining()){
            System.out.println("succeed");
        }
    }
}



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