很经典的一段代码:

list线程安全

线程锁

定时器

package com.gyarmy.servletListener;



import java.util.Collections;

import java.util.LinkedList;

import java.util.List;

import java.util.ListIterator;

import java.util.Timer;

import java.util.TimerTask;



import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import javax.servlet.http.HttpSession;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;



public class Test2 implements HttpSessionListener,ServletContextListener{

	

	private List<HttpSession> list = Collections.synchronizedList(new LinkedList<HttpSession>());

	private Object lock = new Object();

	

	@Override

	public void sessionCreated(HttpSessionEvent se) {

		// TODO Auto-generated method stub

		HttpSession session  = se.getSession();

		

		

		synchronized (lock) {

			list.add(session);

		}

		

		System.out.println("sessionCreated");

	}



	@Override

	public void sessionDestroyed(HttpSessionEvent se) {

		// TODO Auto-generated method stub

		



		System.out.println("sessionDestroyed");

	}



	@Override

	public void contextDestroyed(ServletContextEvent sce) {

		// TODO Auto-generated method stub

		

	}



	@Override

	public void contextInitialized(ServletContextEvent sce) {

		// TODO Auto-generated method stub

		

		Timer time = new Timer();

		time.schedule(new MyTimeTask(list,lock), 0, 1000*60*5);

	}



}



class MyTimeTask extends TimerTask{



	private List<HttpSession> list;

	private Object lock;

	

	public MyTimeTask(List<HttpSession> list,Object lock)

	{

		this.list = list;

		this.lock = lock;

	}

	@Override

	public void run() {

		// TODO Auto-generated method stub

		

		synchronized (lock) {

			//删除session

			ListIterator<HttpSession> listIterator = list.listIterator();

			while(listIterator.hasNext())

			{

				HttpSession session = listIterator.next();

				

				if(System.currentTimeMillis()-session.getLastAccessedTime()>1000*60*5)

				{

					//删除这个session

					session.invalidate();

					listIterator.remove();

				}

			}

			

		}



	}

		

}