在web项目 我们常常使用拦截器做权限验证和登陆验证 

1.创建一个拦截器实现类 标注@Componet

@Componentpublic class LoginInterceputer implements HandlerInterceptor {    /**     * 进入controller层之前拦截请求     * @param httpServletRequest     * @param httpServletResponse     * @param o 为函数对象     * @return     * @throws Exception     */    @Override    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {        System.out.println(o);        System.out.println("进入controller之前拦截");        return true;    }    @Override    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {        System.out.println("--------------处理请求完成后视图渲染之前的处理操作---------------");    }    @Override    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {        System.out.println("---------------视图渲染之后的操作-------------------------0");    }}

2.通过javaconfig的方式进行拦截器配置

@Configurationpublic class WebConfig implements WebMvcConfigurer {    @Autowired    LoginInterceputer loginInterceputer;    @Override    public void addInterceptors(InterceptorRegistry registry) {        // 自定义拦截器，添加拦截路径和排除拦截路径        registry.addInterceptor(loginInterceputer).addPathPatterns(new String[]{"/**"}).excludePathPatterns(new String[]{"/login"});    }}