JSP Session处理

ASP程序员经常要在global.asa文件内处理Application_start,Session_Start等

事件，如：用户验证、重定向不同编码页面等，十分方便，然而一向颇受欢迎的JSP并不很支持这种处理，除了商业化服务器JRun支持global.jsa以外，竟连应用率极高的开放源码服务器Tomcat都不支持，这给JSP的开发造成不小障碍,虽然早期Tomcat(5.0以前版本)下可以通过以下方式实现Session-start事件处理

1.       添加Session

session.put(“bind.listener”,new MyListener(getServletContext())

2.       定义MyListener类

import javax.servlet.http.*;

import javax.servlet.*;

public class MyListener implements HttpSessionBindingListener

{

        ServletContext context;

        public ODSessionListener(ServletContext context)

        {

               this.context=context;

        }

        public void valueBound(HttpSessionBindingEvent event)

        {

               System.out.println(“bound”);

        }

        public void valueUnBound(HttpSessionBindingEvent event)

        {

               System.out.println(“unbound”);

        }

}

但处理前提是Session已经建立，并且不能在Session创建时处理验证等事件，通过研究Servlet 2.4（Tomcat5.0内建）终于找到一种可行方法，实现方法如下：

//---------------------- SessionListener.java----------------------------------------------------

package listeners;

import javax.servlet.ServletContext;

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;

// ServletRequestListener为Servlet2.4新增接口
import javax.servlet.ServletRequestListener;

import javax.servlet.ServletRequestEvent;

import javax.servlet.http.HttpServletRequest;

public final class SessionListener

implements HttpSessionListener,ServletRequestListener {

private  HttpServletRequest  request;

public void requestDestroyed(ServletRequestEvent sre) { }

public  void requestInitialized(ServletRequestEvent sre)

 {

          request=(HttpServletRequest)sre.getServletRequest();

    }

    public void sessionCreated(HttpSessionEvent event) {

        String logMsg=event.getSession().getId()

            +"'  '"+request.getRemoteAddr()

            +":"+request.getRemotePort();

        log("sessionCreated('" + logMsg + "')");

    }

    public void sessionDestroyed(HttpSessionEvent event)