NIO-Reactor模式介绍

Reactor模式常用于java nio编程中，跟生产者消费者模式有点类似，可以认为是只有一个线程的生产者消费者模型，netty底层也是使用Reactor模式作为nio部分的开发

一个简单的Reactor模式

Reactor.java

package com.gbcom.protocol.nio.core;

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

/**
 * 反应器模式，适合nio编码，类似事件驱动编程方式，适合非阻塞IO
 * 
 * 相比较传统的生产者消费者模式，，由于结合nio，不需要开启多个消费者线程，仅仅需要开启一个Reactor线程进行轮询
 * 性能会更高，（reactor 模式 必须结合 nio 也就是 非阻塞的模式使用）
 * 
 * 
 * netty 使用 reactor模式nio部分的编码
 * @author SYZ
 * @date 2016-11-1 上午10:52:58
 * @version 1.0.0
 * @see com.gbcom.protocol.nio.core.Reactor
 */
class Reactor implements Runnable {
	final Selector selector;
	final ServerSocketChannel serverSocket;

	Reactor(int port) throws IOException {
		selector = Selector.open();
		serverSocket = ServerSocketChannel.open();
		serverSocket.socket().bind(new InetSocketAddress(port));
		serverSocket.configureBlocking(false);
		SelectionKey sk = serverSocket.register(selector,
				SelectionKey.OP_ACCEPT);
		sk.attach(new Acceptor());
	}

	/*
	 * Alternatively, use explicit SPI provider: SelectorProvider p =
	 * SelectorProvider.provider(); selector = p.openSelector(); serverSocket =
	 * p.openServerSocketChannel();
	 */
	// class Reactor continued
	public void run() { // normally in a new Thread
		try {
			while (!Thread.interrupted()) {
				selector.select(); //select这个函数是block，
				Set selected = selector.selectedKeys();
				Iterator it = selected.iterator();
				while (it.hasNext())
					dispatch((SelectionKey) (it.next()));
				selected.clear();
			}
		} catch (IOException ex) { /* ... */
		}
	}

	void dispatch(SelectionKey k) {
		Runnable r = (Runnable) (k.attachment());
		if (r != null)
			r.run();
	}

	// class Reactor continued //接收者处理方法
	class Acceptor implements Runnable {
		// inner
		public void run() {
			try {
				SocketChannel c = serverSocket.accept();//1.select()方法仅仅通知有事件到来， 真正的接受 还是要使用 accept
				//每个客户端 应该只执行一次，也就是 new Handler 会重新注册到该select中，以后不会再重复创建了。。。（待测试）
				if (c != null)
					new Handler(selector, c);
			} catch (IOException ex) { /* ... */
			}

		}
	}
	
	/**
	 * Test: (Reactor.main)
	 * @param args
	 * @throws IOException
	 */
	public static void main(String args[]) throws IOException{
		System.out.println(SelectionKey.OP_ACCEPT);
		Reactor reactor = new Reactor(1107);
		Thread t = new Thread(reactor);
//		t.setDaemon(true);
		t.start();
	}
}

Handler.java

package com.gbcom.protocol.nio.core;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;

/**
 * 请求的处理，sk.attach(this);是关键，，也就是直接添加到 选择器中，，如果有事件到来，，直接会调用run方法
 * 
 * 注意 该方法并没有开启线程处理
 * 
 * @author SYZ
 * @date 2016-11-1 上午11:08:04
 * @version 1.0.0
 * @see com.gbcom.protocol.nio.core.Handler
 */
final class Handler implements Runnable {
	final SocketChannel socket;
	final SelectionKey sk;
	ByteBuffer input = ByteBuffer.allocate(0);
	ByteBuffer output = ByteBuffer.allocate(100);
	static final int READING = 0, SENDING = 1;
	int state = READING;

	Handler(Selector sel, SocketChannel c) throws IOException {
		socket = c;
		c.configureBlocking(false);
		// Optionally try first read now
		sk = socket.register(sel, 0);//把channel 注册到选择器中
		sk.attach(this);// 添加到 select中,公用 reactor中的selector线程
		sk.interestOps(SelectionKey.OP_READ);
		sel.wakeup();// 立即执行
	}

	boolean inputIsComplete() {
		return false; /* ... */
	}

	boolean outputIsComplete() {
		return false; /* ... */
	}

	void process() {
		System.out.println("process!");
		/* ... */
	}

	// class Handler continued
	public void run() {
		try {
			if (state == READING)
				read();//IO的read是非阻塞的，但是逻辑是同步，所以有耗时的可能
			else if (state == SENDING)
				send();
		} catch (IOException ex) { /* ... */
		}
	}

	void read() throws IOException {
		socket.read(input);
		if (inputIsComplete()) {
			process();

			state = SENDING;// Normally also do first write now
			sk.interestOps(SelectionKey.OP_WRITE);

			// 设计模式方式
			/*
			 * sk.attach(new Sender()); sk.interest(SelectionKey.OP_WRITE);
			 * sk.selector().wakeup();
			 */

		}
	}

	void send() throws IOException {
		socket.write(output);
		if (outputIsComplete())
			sk.cancel();
	}

	/**
	 * 简单封装，并没有使用
	 * @author SYZ
	 * @date 2016-11-1 上午11:21:38
	 * @version 1.0.0
	 * @see com.gbcom.protocol.nio.core.Sender
	 */
	class Sender implements Runnable {
		public void run() { // ...
			try {
				socket.write(output);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			if (outputIsComplete())
				sk.cancel();
		}
	}

}

以上模式在正常非阻塞IO的情况效果还可以，但是要提供效率，可以使用多线程处理 io之后的业务逻辑，下面看一下多线程Reactor模式

多线程Reactor模式
ReactorWithPool.java

package com.gbcom.protocol.nio.core;

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

/**
 * 反应器的多线程版本，
 * 
 * http://gee.cs.oswego.edu Multiple Reactor Threads " Using Reactor Pools Use
 * to match CPU and IO rates Static or dynamic construction " Each with own
 * Selector, Thread, dispatch loop Main acceptor distributes to other reacto
 * 
 * 
 * 选择器也会资源紧张（未深究），所以可以创建多个
 * @author SYZ
 * @date 2016-11-1 上午11:46:49
 * @version 1.0.0
 * @see com.gbcom.protocol.nio.core.ReactorWithPool
 */
class ReactorWithPool implements Runnable {
	final Selector mainSelector;
	Selector[] subselectors = new Selector[10];//业务逻辑相关的选择器，，如何创建？？
	// also create threads
	int next = 0;

	final ServerSocketChannel serverSocket;

	ReactorWithPool(int port) throws IOException {
		mainSelector = Selector.open();
		
		for(int i=0;i<10;i++){ //add by myself
			subselectors[i] = Selector.open();
		}
		
		serverSocket = ServerSocketChannel.open();
		serverSocket.socket().bind(new InetSocketAddress(port));
		serverSocket.configureBlocking(false);
		SelectionKey sk = serverSocket.register(mainSelector,
				SelectionKey.OP_ACCEPT);
		sk.attach(new Acceptor());
	}

	/*
	 * Alternatively, use explicit SPI provider: SelectorProvider p =
	 * SelectorProvider.provider(); selector = p.openSelector(); serverSocket =
	 * p.openServerSocketChannel();
	 */
	// class Reactor continued
	public void run() { // normally in a new Thread
		try {
			while (!Thread.interrupted()) {
				mainSelector.select();
				Set selected = mainSelector.selectedKeys();
				Iterator it = selected.iterator();
				while (it.hasNext())
					dispatch((SelectionKey) (it.next()));
				selected.clear();
			}
		} catch (IOException ex) { /* ... */
		}
	}

	void dispatch(SelectionKey k) {
		Runnable r = (Runnable) (k.attachment());
		if (r != null)
			r.run();
	}

	// class Reactor continued //接收者处理方法
	class Acceptor implements Runnable {
		// inner
		public void run() {
			try {
				SocketChannel connection = serverSocket.accept();
				if (connection != null)
					new Handler(subselectors[next], connection);
				if (++next == subselectors.length)
					next = 0;
			} catch (IOException e) {
				e.printStackTrace();
			}

		}
	}

	/**
	 * Test: (Reactor.main)
	 * 
	 * @param args
	 * @throws IOException
	 */
	public static void main(String args[]) throws IOException {
		System.out.println(SelectionKey.OP_ACCEPT);
		ReactorWithPool reactor = new ReactorWithPool(1107);
		Thread t = new Thread(reactor);
		t.setDaemon(true);
		t.start();
	}
}

HandlerWithPool.java

package com.gbcom.protocol.nio.core;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;

import EDU.oswego.cs.dl.util.concurrent.PooledExecutor;


/**
 * 使用线程池处理read之后的事情，主要包括业务逻辑，
 * 注意是处理IO read完之后的事情，不是处理IO的读写操作，适用于业务逻辑比较复杂的情况，
 * 
 * 解决逻辑耗时问题
 * 
 * @author SYZ
 * @date 2016-11-1 上午11:33:03
 * @version 1.0.0
 * @see com.gbcom.protocol.nio.core.HandlerWithPool
 */
public class HandlerWithPool implements Runnable{

	  // uses util.concurrent thread pool
	  static PooledExecutor pool = new PooledExecutor();
	  static final int PROCESSING = 3;
	  
	final SocketChannel socket;
	final SelectionKey sk;
	ByteBuffer input = ByteBuffer.allocate(0);
	ByteBuffer output = ByteBuffer.allocate(100);
	static final int READING = 0, SENDING = 1;
	int state = READING;

	HandlerWithPool(Selector sel, SocketChannel c) throws IOException {
		socket = c;
		c.configureBlocking(false);
		// Optionally try first read now
		sk = socket.register(sel, 0);
		sk.attach(this);// 添加到 select中,公用 reactor中的selector线程
		sk.interestOps(SelectionKey.OP_READ);
		sel.wakeup();// 立即执行
	}

	boolean inputIsComplete() {
		return false; /* ... */
	}

	boolean outputIsComplete() {
		return false; /* ... */
	}

	void process() {
		System.out.println("process!");
		/* ... */
	}

	// class Handler continued
	public void run() {
		try {
			if (state == READING)
				read();
			else if (state == SENDING)
				send();
		} catch (IOException ex) { /* ... */
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	synchronized  void read() throws IOException, InterruptedException {
	    socket.read(input);//非阻塞，模式，直接获取了数据，
	    if (inputIsComplete()) {
	      state = PROCESSING;
	      pool.execute(new Processer());
	    }
	}
	
  synchronized void processAndHandOff() {
	    process();
	    state = SENDING; // or rebind attachment
	    sk.interestOps(SelectionKey.OP_WRITE);
	  }
	  class Processer implements Runnable {
	    public void run() { processAndHandOff(); }
	  }
		  

	void send() throws IOException {
		socket.write(output);
		if (outputIsComplete())
			sk.cancel();
	}

	/**
	 * 简单封装，并没有使用
	 * @author SYZ
	 * @date 2016-11-1 上午11:21:38
	 * @version 1.0.0
	 * @see com.gbcom.protocol.nio.core.Sender
	 */
	class Sender implements Runnable {
		public void run() { // ...
			try {
				socket.write(output);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			if (outputIsComplete())
				sk.cancel();
		}
	}


	

}

NIO-Reactor模式介绍

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