写一个springboot的拦截器

好的，下面是一个简单的 Spring Boot 拦截器示例：

1. 创建一个拦截器类实现 HandlerInterceptor 接口：

@Component
public class MyInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("Before handling the request");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("After handling the request");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("After rendering the view");
    }
}

2. 在 Spring Boot 应用程序类中注册拦截器：

@SpringBootApplication
public class MyApp {

    public static void main(String[] args) {
        SpringApplication.run(MyApp.class, args);
    }

    @Autowired
    private MyInterceptor myInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(myInterceptor);
    }
}

这样，Spring Boot 应用程序中就有了一个名为 "myInterceptor" 的拦截器，它将在每个请求被处理之前和之后执行一些操作。