JavaWeb - 过滤器之登录

package com.imooc.sm.global;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class LoginFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request=(HttpServletRequest)servletRequest;
        HttpServletResponse response = (HttpServletResponse)servletResponse;
        String path = request.getServletPath();
        if(path.toLowerCase().indexOf("login")!=-1){
            filterChain.doFilter(request,response);
        }
        else{
            HttpSession session = request.getSession();
            Object obj =session.getAttribute("USER");
            if(obj!=null){
                filterChain.doFilter(request,response);
            }
            else{
                response.sendRedirect(request.getContextPath()+"/toLogin.do");
            }
        }
    }
    public void destroy() {
    }
}

<filter>
  <filter-name>Login</filter-name>
  <filter-class>com.imooc.sm.global.LoginFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>Login</filter-name>
  <url-pattern>*.jsp</url-pattern>
</filter-mapping>
<filter-mapping>
  <filter-name>Login</filter-name>
  <url-pattern>*.do</url-pattern>
</filter-mapping>