一个简单的异步Http连接器

      前两天看了Tomcat连接器部分的源码，Tomcat 4默认的连接器随意已经过时了，但是是一个很好的学习工具。它里面用了多线程的机制使得HttpProcesor异步处理。我但是也是看了很长时间，最后大部分看懂了，但是还有很多没有看懂。我自己写了一个很简单的一个连接器HttpConnector，一个HttpProcessor，帮助大家理解它，先看看程序吧。


BootStrap类很简单，就是使得HttpConnector监听socket请求，这个很好理解。

public class BootStrap {
	public static void main(String[] args){
		HttpConnector connector = new HttpConnector();
		connector.start();
		System.out.println("Server is started, listened in 9999!");
	}
}

    下面是一个比较复杂的HttpConnector类，它首先会创建ServerSocket,然后启动线程，创建minProcessors个HttpProcesor，并使它们都启动起来。

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Stack;


public class HttpConnector implements Runnable{
	private ServerSocket serverSocket;
	
	private int minProcessors = 1;
	
	private int maxProcessors = 5;
	
	private int curProcessors = 0;
	
	private Stack<HttpProcessor> processors = new Stack<HttpProcessor>();
	
	private boolean stopped = false;
	
	public void run() {
		try {
			while(!stopped){
				Socket socket = serverSocket.accept();
				
				HttpProcessor processor = createProcessor();
				
				if(processor != null) {
					processor.assign(socket);
				} else {
					System.out.println("Socket is no resource to be handled!");
				}
				
				socket.close();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public void recycle(HttpProcessor processor){
		processors.push(processor);
	}
	
	public void start(){
		try {
			serverSocket = new ServerSocket(9999);
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		Thread thread = new Thread(this);
		thread.start();
		
		while(curProcessors < minProcessors){
			if(maxProcessors > 0 && curProcessors >= maxProcessors){
				break;
			}
			HttpProcessor processor = newProcessor();
			processors.push(processor);
		}
	}

	private HttpProcessor newProcessor() {
		HttpProcessor processor = new HttpProcessor(this,curProcessors++);
		processor.start();
		return processor;
	}
	
	private HttpProcessor createProcessor(){
		synchronized(processors){
			if(processors.size() > 0){
				return processors.pop();
			} else {
				if(maxProcessors > 0 && curProcessors < maxProcessors){
					return newProcessor();
				} else {
					if(maxProcessors < 0){
						return newProcessor();
					} else {
						return null;
					}
				}
			}
		}
	}
	
}

      下来一个是HttpProcessor，在线程启动后，会调用await方法，使得当前线程等待，有个Socket请求来临之后，调用assign方法，使得当前线程继续运行，但是assign方法会返回，HttpConnector就可以继续相应请求了。在HttpProcessor处理完了之后，HttpPrcoessor会重新放到栈中，就可以进行复用了。这个来的线程同步感觉看了很久还是明白了，但是我估计
现在还写不出来。

import java.net.Socket;


public class HttpProcessor implements Runnable{
	private HttpConnector connector;
	
	private int processorId;
	
	private Socket socket;
	
	private boolean avaliable = false;
	
	private boolean stopped = false;
	
	public HttpProcessor(HttpConnector connector, int processorId){
		this.connector = connector;
		this.processorId = processorId;
	}
	
	public void run(){
		while(!stopped){
			Socket socket = await();
			
			process(socket);
			
			connector.recycle(this);	
		}
	}
	
	public void process(Socket socket){
		System.out.println("Processor " + processorId + " Process socket :" + socket.getPort());
	}
	
	public void start(){
		Thread thread = new Thread(this);
		thread.start();
	}
	
	public synchronized Socket await(){
		while(!avaliable){
			try {
				System.out.println("Process " + processorId + " is ready!");
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		
		avaliable = false;
		Socket socket = this.socket;
		notifyAll();
		return socket;
	}
	
	public synchronized void assign(Socket socket){
		while(avaliable){
			try {
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		avaliable = true;
		this.socket = socket;
		notifyAll();
	}
}

     最后贴上客户端程序，这个我们是来测试服务器端运行的，也很好理解。

import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;


public class Client {
	public static void main(String[] args){
		for(int i = 0; i < 100; i++){
			Socket socket = null;
			try {
				socket = new Socket(InetAddress.getByName("127.0.0.1"),9999);
				System.out.println("Socket is started, socket id is:" + socket.getPort());
			} catch (UnknownHostException e) {
				e.printStackTrace();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}