import  javax.servlet.http.*;
 import  javax.servlet.*;
 import  java.io.IOException;
 public   class  CheckUser  implements  Filter{
     public   void  init(FilterConfig filterConfig)  throws  ServletException {

    }
     public   void  doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)  throws  IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest)servletRequest;
        HttpSession session = req.getSession();
        Object user_id = session.getAttribute("user_id");
         if (user_id !=  null ){
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            
        }
    }
     public   void  destroy() {

    }
}