eventqueue.java

java异步事件池

/*
 * Created on 2003-12-8
 *
 * To change the template for this generated file go to
 * Window - Preferences - Java - Code Generation - Code and Comments
 */
package com.product.util.event;

import java.util.Vector;

import com.product.util.CollectionUtil;




/**
 * @author Renzhichao
 *
 * To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Generation - Code and Comments
 */
public final class EventQueue {
    private Vector queue ;
    
    class Semaphore {
        private int count;
        public Semaphore(int n) {
            this.count = n;
        }

        public synchronized void acquire() {
            while(count == 0) {
                try {
                    wait();
                } catch (InterruptedException e) {
                    //keep trying
                }
            }
            count--;
        }
        
        public synchronized void release() {
            count++;
            notifyAll(); //alert a thread that's blocking on this semaphore
        }
    }
    
    Semaphore sem = null ;//信号量！

    
    private void loadQueue(){
        Event[] evts = EventSerialManager.load() ;        
        queue = CollectionUtil.getInstance().convertArrarToVetor(evts) ;
        if (null==queue){
            queue = new Vector() ;
        }
        sem = new Semaphore(queue.size()) ;
    }
    
    private static EventQueue inst = new EventQueue() ;
    
    private EventQueue(){
        loadQueue() ;        
    }
    
    public static EventQueue getInstance(){
        return inst ;
    }
    
    /**
     * 将一个Event放入到队列中来！
     * 这个Event如果没有序列化，会自动进行序列化！
     * @param evt
     */
    public void putEvent(Event evt){        
        //首先判断这个Event是否是已经序列化的！
        if (!evt.isSerialized()){
            EventSerialManager.writeEvent(evt) ;
        }
        //用生产者模式来激活所有的消费者。
        queue.add(evt) ;
        sem.release() ;
    }
        
    /**
     * 如果队列不为空，返回第一个Event。
     * 如果队列为空，返回空。
     * @return
     */
    public synchronized Event getEvent(){
        sem.acquire() ;//消费者线程获得信号量。
        if (null!=queue&&queue.size()>0){
            return (Event) queue.remove(0) ;
        }
        else { 
            return null ;
        }
    }
    
    public synchronized Event getEvent(String className){
        sem.acquire() ;
        if (null!=queue&&queue.size()>0){
            if (queue.get(0).getClass().getName().equals(className)){
                return (Event)queue.remove(0) ;
            }
            else {
                sem.release() ;
                return null ;
            }
        }
        else {            
            return null ;
        }
    }
}