过滤器实现登录拦截

@WebFilter(urlPatterns = {"/*"})
public class LoginFiilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest servletRequest1=(HttpServletRequest) request;
        //放行URL
        if (servletRequest1.getRequestURI().equals("/user/login")){
            filterChain.doFilter(request,response);
        }
        Object user = servletRequest1.getSession().getAttribute("user");
        if (user==null){
            servletRequest1.getRequestDispatcher("/login.jsp").forward(request,response);
        }else {
            //放行请求
            filterChain.doFilter(request,response);
        }
    }
    @Override
    public void destroy() {
    }
}