通知控制器方法 *before* @Valid 注释被处理 [英] advise controller method *before* @Valid annotation is handled

问题描述

我正在使用 Spring MVC 4.1 向一个安静的网络服务添加速率限制.

I am adding rate-limiting to a restful webservice using Spring MVC 4.1.

我创建了一个可以应用于控制器方法的 @RateLimited 注释.Spring AOP 方面会拦截对这些方法的调用，并在请求过多时抛出异常:

I created a @RateLimited annotation that I can apply to controller methods. A Spring AOP aspect intercepts calls to these methods and throws an exception if there have been too many requests:

@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class RateLimitingAspect {

    @Autowired
    private RateLimitService rateLimitService;

    @Before("execution(* com.example..*.*(.., javax.servlet.ServletRequest+, ..)) " +
            "&& @annotation(com.example.RateLimited)")
    public void wait(JoinPoint jp) throws Throwable {

        ServletRequest request =
            Arrays
                .stream(jp.getArgs())
                .filter(Objects::nonNull)
                .filter(arg -> ServletRequest.class.isAssignableFrom(arg.getClass()))
                .map(ServletRequest.class::cast)
                .findFirst()
                .get();
        String ip = request.getRemoteAddr();
        int secondsToWait = rateLimitService.secondsUntilNextAllowedAttempt(ip);
        if (secondsToWait > 0) {
          throw new TooManyRequestsException(secondsToWait);
        }
    }

这一切都很完美，除非 @RateLimited 控制器方法的参数标记为 @Valid，例如:

This all works perfectly, except when the @RateLimited controller method has parameters marked as @Valid, e.g.:

@RateLimited
@RequestMapping(method = RequestMethod.POST)
public HttpEntity<?> createAccount(
                           HttpServletRequest request,
                           @Valid @RequestBody CreateAccountRequestDto dto) {

...
}

问题:如果验证失败，验证器抛出MethodArgumentNotValidException，由@ExceptionHandler处理，返回错误响应给客户端，永远不会触发我的@Before 从而绕过速率限制.

The problem: if validation fails, the validator throws MethodArgumentNotValidException, which is handled by an @ExceptionHandler, which returns an error response to the client, never triggering my @Before and therefore bypassing the rate-limiting.

如何以优先于参数验证的方式拦截这样的网络请求?

我想过使用 Spring Interceptors 或普通 servlet 过滤器，但它们是通过简单的 url-patterns 映射的，我需要通过 GET/POST/PUT/etc 进行区分.

I've thought of using Spring Interceptors or plain servlet Filters, but they are mapped by simple url-patterns and I need to differentiate by GET/POST/PUT/etc.

推荐答案

我最终放弃了寻找 AOP 解决方案的尝试，而是创建了一个 Spring Interceptor.拦截器 preHandle 处理所有请求并监视处理程序为 @RateLimited 的请求.

I eventually gave up on trying to find an AOP solution and created a Spring Interceptor instead. The interceptor preHandles all requests and watches for requests whose handler is @RateLimited.

@Component
public class RateLimitingInterceptor extends HandlerInterceptorAdapter {

    @Autowired
    private final RateLimitService rateLimitService;

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

        if (HandlerMethod.class.isAssignableFrom(handler.getClass())) {
            rateLimit(request, (HandlerMethod)handler);
        }
        return super.preHandle(request, response, handler);
    }

    private void rateLimit(HttpServletRequest request, HandlerMethod handlerMethod) throws TooManyRequestsException {

        if (handlerMethod.getMethodAnnotation(RateLimited.class) != null) {
            String ip = request.getRemoteAddr();
            int secondsToWait = rateLimitService.secondsUntilNextAllowedInvocation(ip);
            if (secondsToWait > 0) {
                throw new TooManyRequestsException(secondsToWait);
            } else {
                rateLimitService.recordInvocation(ip);
            }
        }
    }
}

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