SpringBoot中拦截器接口：

public interface HandlerInterceptor {
    default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }

    default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
    }

    default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
    }
}

        执行顺序：

                preHandle -> controller中的目标方法 -> postHandle -> afterCompletion(请求处理完成之后)

拦截器设置流程：

1、拦截器的业务逻辑

        需要实现HandlerInteceptor接口

public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HttpSession session = request.getSession();
        Object loginUser = session.getAttribute("loginUser");
        if(loginUser!=null){
            return true;
        }
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}

  2、把配置放在容器中

//配置web功能的都需要实现WebMvcConfigurer,
@Configuration
public class AdminWebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/","/login","/css/**","/fonts/**","/images/**","/js/**");
    }
}

        WebMvcConfigurer接口中有许多web功能：

public interface WebMvcConfigurer {

    default void addInterceptors(InterceptorRegistry registry) {
    }

    default void addResourceHandlers(ResourceHandlerRegistry registry) {
    }

    default void addCorsMappings(CorsRegistry registry) {
    }

    default void addViewControllers(ViewControllerRegistry registry) {
    }

    default void configureViewResolvers(ViewResolverRegistry registry) {
    }

    default void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
    }

    default void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> handlers) {
    }

    default void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    }

......

        增加拦截路径和排除拦截路径：

registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**") //会拦截所有的请求，也包括静态资源
                .excludePathPatterns("/","/login","/css/**","/fonts/**","/images/**","/js/**");

   记录一下/**和/*的区别：

SpringMVC 拦截器拦截 /* 和 /** 的区别：_Simba1949的博客-CSDN博客

        实验：

 将静态资源下的 fonts文件和css文件中设置为/*，然后看访问时候能否放行：

首先是css下的文件：

 css下没有任何文件夹了，直接都是文件，按链接里的解释，是可以访问到的。

接着测试fonts文件夹下，按链接意思应该是会被拦截的：

 所以很明确了：xxx/*的范围只是针对到xxx/  下的所有文件，不会包含文件夹

                        xxx/**的范围就是 xxx/ 下的所有文件夹和文件。