onlinecounterlistener.java

来自「IBM提供的购物车」· Java 代码 · 共 44 行

package com.webshop.listener;

import javax.servlet.http.*;
import javax.servlet.*;

/**
 * @version 	1.0
 * @author
 */
public class OnLineCounterListener implements HttpSessionListener {

private int count;
	private ServletContext context = null;
	
	public OnLineCounterListener()
	{
		count=0;
		//setContext();
	}
	//创建一个session时激发
	public void sessionCreated(HttpSessionEvent se) 
	{
		count++;
		setContext(se);
		
	}
	//当一个session失效时激发
	public void sessionDestroyed(HttpSessionEvent se) 
	{
		count--;
		setContext(se);
	}
	//设置context的属性，它将激发attributeReplaced或attributeAdded方法
	public void setContext(HttpSessionEvent se)
	{
		if(context==null)
		context=se.getSession().getServletContext();
		context.setAttribute("onLine",new Integer(count));
		
	}	
   

}