@Component

public class LoginHandlerInterceptor implements HandlerInterceptor {

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

       //拦截逻辑

        Object user = request.getSession().getAttribute("loginUser");

        if (user == null) {

            System.out.println("没有权限请先登陆");

            //未登陆，返回登陆界面

            request.setAttribute("msg","没有权限请先登陆");

            request.getRequestDispatcher("/login").forward(request,response);

            return false;

        } else {

            //已登陆，放行请求

            return true;

        }

    }

}

@Configuration

public class MyWebMvcConfiguration implements WebMvcConfigurer {

    @Autowired

    LoginHandlerInterceptor loginHandlerInterceptor;

    @Override

    public void addViewControllers(ViewControllerRegistry registry) {

        registry.addViewController("/").setViewName("forward:/login");

        registry.setOrder(Ordered.HIGHEST_PRECEDENCE);

    }

    //注册拦截器

    @Override

    public void addInterceptors(InterceptorRegistry registry) {

        //拦截所有的请求

        registry.addInterceptor(loginHandlerInterceptor).addPathPatterns("/**").excludePathPatterns("/login", "/register").excludePathPatterns("/static/**");

    }

}