JAVA过滤器，实现登陆权限限制

java代码:
package com.unionx.wanxue.utils;


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;


import com.unionx.wanxue.domains.UserServiceDTD;


public class LoginFilter implements Filter {


@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub


}


@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
// TODO Auto-generated method stub
 HttpServletRequest httprequest = (HttpServletRequest)request;
   HttpServletResponse httpresponse = (HttpServletResponse)response;
   HttpSession session = httprequest.getSession();
   UserServiceDTD userInfo =(UserServiceDTD)session.getAttribute("userinfo");
   String uri = httprequest.getRequestURI();
//assets，css,lib等url不过滤
   if(uri.contains("/assets/")){
    chain.doFilter(request, response);
   }else if(uri.contains("/css/")){
    chain.doFilter(request, response);
   }else if(uri.contains("/lib/")){
    chain.doFilter(request, response);
   }else if(uri.contains("/js/")){
    chain.doFilter(request, response);
   }else if(uri.contains("/login")){
    chain.doFilter(request, response);
   }else if(uri.contains("/skin")){
    chain.doFilter(request, response);
   }
   else if(uri.contains("/images/")){
    chain.doFilter(request, response);
   }
   else if(uri.contains("/cc/")){
    chain.doFilter(request, response);
   }
   else{
   
    if(userInfo==null){
   
    httprequest.setAttribute("info", "helloword!");
    httprequest.getRequestDispatcher("/login.jsp").forward(httprequest, httpresponse);
    }else{
    chain.doFilter(request, response);
    }
   }
   // http://localhost:8080/meeting/servlet
}


@Override
public void destroy() {
// TODO Auto-generated method stub


}


}


web.xml配置
<filter>
    <filter-name>LoginFilters</filter-name>
    <filter-class>com.unionx.wanxue.utils.LoginFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>LoginFilters</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>