NIO Reactor模型(含代码)

已于 2023-03-30 09:45:37 修改
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分类专栏： Java 文章标签： nio Reactor模型 网络编程 java
于 2023-03-29 21:03:50 首次发布
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本文链接：https://blog.youkuaiyun.com/longqicsdn/article/details/129843568
文章详细介绍了NIO中的Reactor模型，包括单Reactor单线程和单Reactor多线程两种实现方式。在单线程模型中，整个服务器的执行流程都在同一个线程中顺序进行，而多线程模型则引入线程池来提高处理速度。代码示例展示了如何使用Selector注册事件并分发到相应的处理器进行处理。

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概览

        我们知道NIO就是调用系统内核的的select/poll/epoll方法来实现，这些系统内核方法会扫描或监控IO，每次将所有的IO的状态返回给NIO线程。让NIO线程可以选择处理读取可读状态的IO流，也可以选择继续监控轮询监控IO的其它状态。

        reactor模型也叫做Dispatcher模型，即分发模型，NIO中分发线程和处理线程策略不同而衍生出了四种网络编程模型：单Reactor单线程、单Reactor多线程、多Reactor多线程。

单Reactor单线程

       这里无非就是整个NIO Server里都是单线程顺序执行，Reactor调用select()方法IO状态为ACCEPT就派发给Acceptor处理，IO状态为OP_READ或OP_WRITE则派发给handler进行处理。

上图Reactor获取到IO状态后，依旧是单线程按顺序进行处理。具体代码如下：

package com.longqi.boottest.io;

import java.net.InetSocketAddress;
import java.net.Socket;
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.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * @author LongQi
 * @projectName boot-integration
 * @description: TODO
 * @date 2023/3/29 20:06
 */

public class SingleReactorSingleThread {

    public static void main(String[] args) {
        int port = 8080;
        Server server = new Server(port);
        server.start();
        sendMessage(port);
    }

    static class Server{
        private int port;
        public Server(int port){
            this.port=port;
        }
        public void start(){
            try {
                ServerSocketChannel server = ServerSocketChannel.open();
                server.configureBlocking(false);
                server.socket().bind(new InetSocketAddress(port));
                Selector selector = Selector.open();
                // 设置select监听的事件
                server.register(selector, SelectionKey.OP_ACCEPT);
                new Thread(new Reactor(selector)).start();
            }catch (Exception e){
                System.out.println("服务器启动失败:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class Reactor implements Runnable{
        private Selector selector;
        private Dispatch dispatch = new Dispatch();
        public Reactor(Selector selector){
            this.selector=selector;
        }

        @Override
        public void run() {
            try{
                while (true){
                    int n = selector.select();
                    if(n > 0){
                        Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                        while (iterator.hasNext()){
                            SelectionKey key = iterator.next();
                            dispatch.dispatch(selector,key);
                            iterator.remove();
                        }
                    }
                }
            }catch (Exception e){
                System.out.println("服务器运行异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class Dispatch{
        private ReadHandler handler = new ReadHandler();
        private Acceptor acceptor = new Acceptor();

        public void dispatch(Selector selector,SelectionKey key){
            if(key.isAcceptable()){
                acceptor.hand(selector,key);
            }
            if(key.isReadable()){
                handler.hand(key);
            }
        }
    }

    static class Acceptor{
        public void hand(Selector selector,SelectionKey key){
            try{
                ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
                SocketChannel clientChannel = serverChannel.accept();
                clientChannel.configureBlocking(false);
                clientChannel.register(selector,SelectionKey.OP_READ);
            }catch (Exception e){
                System.out.println("处理请求异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class ReadHandler{
        public void hand(SelectionKey key){
            try{
                SocketChannel channel = (SocketChannel) key.channel();
                ByteBuffer buffer = ByteBuffer.allocate(1024);
                while (channel.read(buffer)!=-1){
                    //复位，转化为读模式
                    buffer.flip();
                    while (buffer.hasRemaining()){
                        System.out.println("收到客户端"+channel.socket().getPort()+"的信息："+ StandardCharsets.UTF_8.decode(buffer).toString());
                    }
                    //清空缓存区，转化为写模式
                    buffer.clear();
                }
            }catch (Exception e){
                System.out.println("处理请求异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    public static void sendMessage(int port) {
        try{
            Thread.sleep(2000);
            ThreadPoolExecutor clientPool = new ThreadPoolExecutor(200,300,60, TimeUnit.SECONDS,new LinkedBlockingQueue<>(800));
            for(int i=0;i<300;i++){
                clientPool.submit(new Runnable() {
                    @Override
                    public void run() {
                        try{
                            Socket client = new Socket();
                            client.connect(new InetSocketAddress("127.0.0.1",port));
                            client.getOutputStream().write(("hello world,send time:"+System.nanoTime()).getBytes());
                            // 注意TCP粘包，这里不调用close，服务器是收不到消息的
                            client.close();
                        }catch (Exception e){
                            System.out.println("客户端发送信息失败");
                        }
                    }
                });
            }
        }catch (Exception e){
            System.out.println("客户端发送信息失败");
        }
    }
}

 单Reactor多线程

       这里NIO Server里都是单个Reactor调用select()方法，然后派发给handler时使用线程池进行处理。大大提升处理速度。

上图Reactor获取到IO状态后，可读可写的channel由线程池开线程进行处理。具体代码如下：

package com.longqi.boottest.io;

import java.net.InetSocketAddress;
import java.net.Socket;
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.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * @author LongQi
 * @projectName boot-integration
 * @description: TODO
 * @date 2023/3/29 20:06
 */

public class SingleReactorMultiThread{

    public static void main(String[] args) {
        int port = 8080;
        Server server = new Server(port);
        server.start();
        sendMessage(port);
    }

    static class Server{
        private int port;
        public Server(int port){
            this.port=port;
        }
        public void start(){
            try {
                ServerSocketChannel server = ServerSocketChannel.open();
                server.configureBlocking(false);
                server.socket().bind(new InetSocketAddress(port));
                Selector selector = Selector.open();
                // 设置select监听的事件
                server.register(selector, SelectionKey.OP_ACCEPT);
                new Thread(new Reactor(selector)).start();
            }catch (Exception e){
                System.out.println("服务器启动失败:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class Reactor implements Runnable{
        private Selector selector;
        private Dispatch dispatch = new Dispatch();
        public Reactor(Selector selector){
            this.selector=selector;
        }

        @Override
        public void run() {
            try{
                while (true){
                    int n = selector.select();
                    if(n > 0){
                        Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                        while (iterator.hasNext()){
                            SelectionKey key = iterator.next();
                            dispatch.dispatch(selector,key);
                            iterator.remove();
                        }
                    }
                }
            }catch (Exception e){
                System.out.println("服务器运行异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class Dispatch{
        private Acceptor acceptor = new Acceptor();
        private ThreadPoolExecutor handPool = new ThreadPoolExecutor(200,300,60, TimeUnit.SECONDS,new LinkedBlockingQueue<>(800));

        public void dispatch(Selector selector,SelectionKey key){
            if(key.isAcceptable()){
                acceptor.hand(selector,key);
            }
            if(key.isReadable()){
                handPool.submit(new ReadHandler(key));
            }
        }
    }

    static class Acceptor{
        public void hand(Selector selector,SelectionKey key){
            try{
                ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
                SocketChannel clientChannel = serverChannel.accept();
                clientChannel.configureBlocking(false);
                clientChannel.register(selector,SelectionKey.OP_READ);
            }catch (Exception e){
                System.out.println("处理请求异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    static class ReadHandler implements Runnable{
        private SelectionKey key;
        public ReadHandler(SelectionKey key){
            this.key = key;
        }

        @Override
        public void run() {
            try{
                SocketChannel channel = (SocketChannel) key.channel();
                ByteBuffer buffer = ByteBuffer.allocate(1024);
                while (channel.read(buffer)!=-1){
                    //复位，转化为读模式
                    buffer.flip();
                    while (buffer.hasRemaining()){
                        System.out.println("收到客户端"+channel.socket().getPort()+"的信息："+ StandardCharsets.UTF_8.decode(buffer).toString());
                    }
                    //清空缓存区，转化为写模式
                    buffer.clear();
                }
            }catch (Exception e){
                System.out.println("处理请求异常:"+e.getMessage());
                e.printStackTrace();
            }
        }
    }

    public static void sendMessage(int port) {
        try{
            Thread.sleep(2000);
            ThreadPoolExecutor clientPool = new ThreadPoolExecutor(200,300,60, TimeUnit.SECONDS,new LinkedBlockingQueue<>(800));
            for(int i=0;i<300;i++){
                clientPool.submit(new Runnable() {
                    @Override
                    public void run() {
                        try{
                            Socket client = new Socket();
                            client.connect(new InetSocketAddress("127.0.0.1",port));
                            client.getOutputStream().write(("hello world,send time:"+System.nanoTime()).getBytes());
                            // 注意TCP粘包，这里不调用close，服务器是收不到消息的
                            client.close();
                        }catch (Exception e){
                            System.out.println("客户端发送信息失败");
                        }
                    }
                });
            }
        }catch (Exception e){
            System.out.println("客户端发送信息失败");
        }
    }
}

 多Reactor多线程

       这里NIO Server里有两个Reactor，一个分发给acceptor，一个分发给处理线程。

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