jsp：通过过滤器进行网页的资源管理

一，本例通过继承servlet下的Filter类并实现。

1，通过登陆页面触发session赋值来确认是否登陆，（详见：jsp:通过Session控制登陆时间和内部页面的访问）

2，此例修改为使用过滤器进行全站的网页权限控制。

以下是Fliter类中代码：

package com.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class UserFilter implements Filter{

    public void destroy() {
        // TODO Auto-generated method stub
        
    }
    
    //实现类doFilter进行权限的控制。
    public void doFilter(ServletRequest arg0, ServletResponse arg1,
            FilterChain arg2) throws IOException, ServletException {
        
        HttpServletRequest req=(HttpServletRequest)arg0;
        HttpServletResponse res=(HttpServletResponse)arg1;
        HttpSession session=req.getSession();
        String user=(String)session.getAttribute("user");
        if(user==null||!"yes".equals(user)){
            res.sendRedirect("/Tree/pages/login.jsp");//没有登陆过跳转到登陆页面
        }else{
            arg2.doFilter(arg0, arg1);//如果该session登陆过便放行
            }
    }

    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        
    }

}

 2，web.XML中配置：

在<

<?xml version="1.0" encoding="UTF-8"?>
<display-name></display-name>
  
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>User</servlet-name>
    <servlet-class>com.in.User</servlet-class>
  </servlet>
  
  
  <filter>
  <filter-name>UserFilter</filter-name>
  <filter-class>com.filter.UserFilter</filter-class>
  </filter>
  
  <filter-mapping>
  <filter-name>UserFilter</filter-name>
  <url-pattern>/session/*</url-pattern>//选择需要过滤的文件夹下的所有网页
  </filter-mapping>
  
  
  
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
</web-app>