继续使用上一个案例 用户不登录无法访问重要的web资源

package com.itbear.myFilter;

import java.io.IOException;
import java.io.PrintWriter;

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;

/**
 * Servlet Filter implementation class ImportFilter
 */
public class ImportFilter implements Filter {

    /**
     * Default constructor. 
     */
    public ImportFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse) response;
        HttpServletRequest req = (HttpServletRequest) request;
        
        PrintWriter out = response.getWriter();
        
        //获取session
        HttpSession session = req.getSession();
        Object obj = session.getAttribute("user");
        
        if(null != obj){
            //登录就放行
            chain.doFilter(request, response);
        }
        else{
            //不登录就 先登录
            out.println("先完成登录");
            res.setHeader("Refresh", "3;URL=/mySession/index.jsp");
        }
        
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

Web.xml路径配置

<filter>
    <display-name>ImportFilter</display-name>
    <filter-name>ImportFilter</filter-name>
    <filter-class>com.itbear.myFilter.ImportFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>ImportFilter</filter-name>
    <url-pattern>/importance/*</url-pattern>
  </filter-mapping>
</filter>
``