mysessionlistener.java

老师给的购物车

package com.tarena.shopcart.listener;

import java.io.FileOutputStream;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MySessionListener implements HttpSessionListener,ServletContextListener {

	ServletContext context;
	int users=0;
	public void sessionCreated(HttpSessionEvent event) {
		users++; 
		logout("sessionCreated('"   +   event.getSession().getId()   +   "'),目前有"+users+"个用户");  
		context.setAttribute("users",new   Integer(users)); 


	}

	public void sessionDestroyed(HttpSessionEvent event) {
		users--;
		logout("sessionDestroyed('"   +   event.getSession().getId()   +   "'),目前有"+users+"个用户");   
		context.setAttribute("users",new   Integer(users));

	}
	private void logout(String message){
		PrintWriter out=null;
		try{
			out=new PrintWriter(new FileOutputStream("c:\\session.txt",true));
			out.println(new java.util.Date().toLocaleString()+"::from Listener: "+message);
			out.close();
		}catch(Exception e){
			out.close();
			e.printStackTrace();
		}
	}

	public void contextDestroyed(ServletContextEvent sce) {
		logout("contextDestroyed()-->ServletContext被销毁");  
	    this.context   =   null; 
		
	}

	public void contextInitialized(ServletContextEvent sce) {
		this.context   =   sce.getServletContext();   
		logout("contextInitialized()-->ServletContext初始化了");
		
	}

}