过滤器之登陆过滤

次过滤器主要用于，判断用户是否登陆，以防直接访问应用中的网页进行提交

Filter 类的写法，

package  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. * ;

import  com.tarena.crm.domain.admin.Manager;

public   class  LoginFilter   extends  HttpServlet   implements  Filter ... {

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException ...{
        HttpServletRequest req=(HttpServletRequest)request;
        HttpServletResponse res=(HttpServletResponse) response;
        if(req.getSession().getAttribute("manager")==null)...{
            res.sendRedirect("/crm/core/login.jsp");
        }else
        chain.doFilter(request, response);        
    }

    public void init(FilterConfig arg0) throws ServletException ...{
        
    }



}

 web.xml中的写法：

<url-pattern>/core/adminManage/*</url-pattern>对一个目录进行过滤

或者：

<url-pattern>/core/adminManage/test.jsp</url-pattern>对某一个特定网页进行过滤

     < filter >
         < filter-name > setlog </ filter-name >
         < filter-class > filter.LoginFilter </ filter-class >
     </ filter >
     < filter-mapping >
         < filter-name > setlog </ filter-name >
         < url-pattern > /core/adminManage/* </ url-pattern >
     </ filter-mapping >