JAVA并发处理经验(四)并行模式与算法6：NIO网络编程

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一、前言

首先我们必须了解NIO的一些基本概念

channel：是NIO中的一个通道，类似我们说的流。---管道

Buffer：理解为byte数组。与channel交流。----水流

Selector：有一个SelectableChancel实现，用线程管理------选择器

二、NIO编程

2.1 NIO服务端

package pattern.nio;import java.io.IOException;import java.net.InetAddress;import java.net.InetSocketAddress;import java.net.ServerSocket;import java.net.Socket;import java.nio.ByteBuffer;import java.nio.channels.*;import java.nio.channels.spi.SelectorProvider;import java.util.*;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * Created by ycy on 16/1/19. */public class NioServer {    //选择器    private Selector selector;    //线程池    private ExecutorService tp = Executors.newCachedThreadPool();    //给定大小的map    public static Map<Socket, Long> time_stat = new HashMap<Socket, Long>(10240);    public void startServer() throws Exception {        //1'由selectorPrivider返回一个创建者,并打开一个选择器        selector = SelectorProvider.provider().openSelector();        //2'打开套接字通道        ServerSocketChannel ssc = ServerSocketChannel.open();        //block - 如果为 true，则此通道将被置于阻塞模式；如果为 false，则此通道将被置于非阻塞模式        ssc.configureBlocking(false);        InetSocketAddress isa = new InetSocketAddress(65500);        // InetSocketAddress isa=new InetSocketAddress(8000);        //获取与此通道关联的服务器套接字。将 ServerSocket 绑定到特定地址（IP 地址和端口号）        ssc.socket().bind(isa);        //将通道注册到选择器,        SelectionKey accpetKey = ssc.register(selector, SelectionKey.OP_ACCEPT);        try {            for (; ; ) {                selector.select();//消费阻塞                Set readykeys = selector.selectedKeys();//获取已经准备好的keys                Iterator i = readykeys.iterator();//迭代                long e = 0;                while (i.hasNext()) {                    SelectionKey sk = (SelectionKey) i.next();                    i.remove();//必须消除,防止重复消费                    if (sk.isAcceptable()) {                        doAccept(sk);//如果为接受状态,接受                    } else if (sk.isValid() && sk.isReadable()) {//如果是可读                        if (!time_stat.containsKey(((SocketChannel) sk.channel()).socket())) {                            //将socket方法如map                            time_stat.put(((SocketChannel) sk.channel()).socket(),                                    System.currentTimeMillis());//增加一个时间戳                            //读取                            doRead(sk);                        }                    } else if (sk.isValid() && sk.isWritable()) {                        //写                        doWrite(sk);                        e = System.currentTimeMillis();                        long b = time_stat.remove(((SocketChannel) sk.channel()).socket());                        System.out.println("spend:" + (e - b) + "ms");//输入处理写入耗时                    }                }            }        } catch (ClosedSelectorException e) {            System.out.println("外面捕捉不做事");        }    }    /*    与客户端建立连接     */    private void doAccept(SelectionKey sk) {        try {            ServerSocketChannel server = (ServerSocketChannel) sk.channel();            SocketChannel clientChannel;            clientChannel = server.accept();//生成一个channel表示与客户端通信            clientChannel.configureBlocking(false);//非阻塞模式            //Register this channel for reading            SelectionKey clientKey = clientChannel.register(selector, SelectionKey.OP_READ);            //Allocate an Echoclient instance adn attach it to this selction key            EchoClient echoClient = new EchoClient();//回复给客服端口的全部信息            clientKey.attach(echoClient);//附加实例,整个连接共享实例            InetAddress clientAddress = clientChannel.socket().getInetAddress();            System.out.println("Acceprted connection form " + clientAddress.getHostAddress() + ".")            ;        } catch (Exception e) {            e.printStackTrace();        }    }    //执行读得操作    private void doRead(SelectionKey sk) {        SocketChannel channel = (SocketChannel) sk.channel();        ByteBuffer bb = ByteBuffer.allocate(8192);        int len;        try {            len = channel.read(bb);            if (len < 0) {                disconnect(sk);                return;            }        } catch (Exception e) {            System.out.println("faild to read from client");            e.printStackTrace();            disconnect(sk);            return;        }        bb.flip();        tp.execute(new HanldeMsg(sk, bb));    }    private void disconnect(SelectionKey sk) {        try {            SocketChannel channel = (SocketChannel) sk.channel();            channel.close();            //sk.cancel();            sk.selector().close();        } catch (IOException e) {            e.printStackTrace();        }    }    //执行写操作    private void doWrite(SelectionKey sk) {        SocketChannel channel = (SocketChannel) sk.channel();        EchoClient echoClient = (EchoClient) sk.attachment();        LinkedList<ByteBuffer> outq = echoClient.getOutputQuquq();        ByteBuffer bb = outq.getLast();        try {            int len = channel.write(bb);            if (len == -1) {                disconnect(sk);                return;            }            if (bb.remaining() == 0) {                //已经完成                outq.removeLast();            }        } catch (Exception e) {            System.out.println("Faild to write to client");            e.printStackTrace();            disconnect(sk);        }        if (outq.size() == 0) {//很重要            sk.interestOps(SelectionKey.OP_READ);        }    }    /////////////////内部匿名类/////////////////////    class EchoClient {        private LinkedList<ByteBuffer> outq;        EchoClient() {            outq = new LinkedList<ByteBuffer>();        }        public LinkedList<ByteBuffer> getOutputQuquq() {            return outq;        }        public void enqueue(ByteBuffer bb) {            outq.addFirst(bb);        }    }    //将接受的数据压入EchClient,需要处理业务在这u处理,处理完成之后重新注册事件op_write    class HanldeMsg implements Runnable {        SelectionKey sk;        ByteBuffer bb;        public HanldeMsg(SelectionKey sk, ByteBuffer bb) {            this.sk = sk;            this.bb = bb;        }        public void run() {            EchoClient echoClient = (EchoClient) sk.attachment();            echoClient.enqueue(bb);            sk.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);            //强迫selector立即返回            selector.wakeup();        }    }}

2.2NIO main方法

package pattern.nio;/** * Created by ycy on 16/1/20. */public class NioMain {    public static void main(String[] args) throws Exception {        NioServer nioServer=new NioServer();        nioServer.startServer();    }}

2.3 NIO客户端

package pattern.nio;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.nio.channels.spi.SelectorProvider;import java.util.Iterator;/** * Created by ycy on 16/1/20. */public class NioClient {    private Selector selector;    public void init(String ip,int port) throws IOException {        SocketChannel channel=SocketChannel.open();        channel.configureBlocking(false);        this.selector= SelectorProvider.provider().openSelector();        channel.connect(new InetSocketAddress(ip,port));        channel.register(selector,SelectionKey.OP_CONNECT);    }    public void working() throws IOException {        while (true){            if (!selector.isOpen()){                break;            }                selector.select();                Iterator<SelectionKey> ite=this.selector.selectedKeys().iterator();                while (ite.hasNext()){                    SelectionKey key=ite.next();                    ite.remove();                    //连接事件                    if (key.isConnectable()){                        connect(key);                    }else if(key.isReadable()){                        read(key);                    }                }        }    }    /*    连接     */    public void connect(SelectionKey key) throws IOException {       SocketChannel channel=(SocketChannel)key.channel();        //如果正在连接,则连接完成        if(channel.isConnectionPending()){            channel.finishConnect();        }        channel.configureBlocking(false);        channel.write(ByteBuffer.wrap(new String("HELLO" ).getBytes()));        channel.register(this.selector,SelectionKey.OP_READ);    }    public void read(SelectionKey key) throws IOException {        SocketChannel channel=(SocketChannel)key.channel();        //读取缓冲区        ByteBuffer bb=ByteBuffer.allocate(1000);        channel.read(bb);        byte[] data=bb.array();        String msg=new String(data).trim();        System.out.println("客户端收到信息:"+msg);        channel.close();        key.selector().close();    }    public static void main(String[] args) throws IOException {        NioClient nioClient=new NioClient();        nioClient.init("127.0.0.1",65500);        nioClient.working();    }}

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