onlinelistener.java

jsp,过滤器和监听器的简单例子

package MyPackage;

import java.util.ArrayList;
import java.util.List;
import MyPackage.UserBean;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class OnlineListener implements ServletContextListener,ServletContextAttributeListener,HttpSessionListener,HttpSessionAttributeListener {
    private ServletContext application = null ; 
    
    public void contextInitialized(ServletContextEvent sce) {        
    	this.application=sce.getServletContext() ; //初始化一个application对象
    	//设置一个列表属性，用于保存在线用户名
    	
    	this.application.setAttribute("online", new ArrayList()) ;    }
           
    public void sessionDestroyed(HttpSessionEvent se) {
        List online=(List)this.application.getAttribute("online") ; //取得用户列表
        UserBean user = (UserBean)se.getSession().getAttribute("user");//取得当前用户
        online.remove(user) ; //将此用户名从列表中删除
        //将删除后的列表重新设置到application属性中
        this.application.setAttribute("online", online) ;
    }
   
    public void attributeAdded(HttpSessionBindingEvent se) {        
    	List online=(List)this.application.getAttribute("online") ; //取得用户列表   	
    	online.add(se.getValue());        //将当前用户添加到列表中
    	this.application.setAttribute("online", online) ; //将添加后的列表重新设置到application属性中
    }

    public void contextDestroyed(ServletContextEvent arg0) {
    	// TODO Auto-generated method stub
	
    }

    public void attributeAdded(ServletContextAttributeEvent arg0) {
    	// TODO Auto-generated method stub
	
    }

    public void attributeRemoved(ServletContextAttributeEvent arg0) {
    	// TODO Auto-generated method stub
	
    }

    public void attributeReplaced(ServletContextAttributeEvent arg0) {
    	// TODO Auto-generated method stub
	
    }

    public void sessionCreated(HttpSessionEvent arg0) {

    }

    public void attributeRemoved(HttpSessionBindingEvent arg0) {
    	// TODO Auto-generated method stub
	
    }

    public void attributeReplaced(HttpSessionBindingEvent arg0) {
    	// TODO Auto-generated method stub
	
    }   
}