项目场景：

最近帮同事在看一个后端接口数据关于类型、长度、字符内容规范化的任务，想到了使用Valid注解的方式来完成，但是在实际使用的时候，发现前后端数据在不同场景下交互方式的差异，会导致Valid注解使用不生效。

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问题描述

@RequestParam数据校验不生效：

public JsonResult createApplication( @NotBlank @Size(min = 1, max = 500) @RequestParam String filePath,……}

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原因分析：

Spring在解析不同入参时，使用不同的解析器，有的解析器会触发Valid逻辑，有的不会。

@RequestParam等非body注解解析器不提供valid逻辑，详见org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver

@Override@Nullablepublic final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);MethodParameter nestedParameter = parameter.nestedIfOptional();Object resolvedName = resolveEmbeddedValuesAndExpressions(namedValueInfo.name);if (resolvedName == null) {throw new IllegalArgumentException("Specified name must not resolve to null: [" + namedValueInfo.name + "]");}Object arg = resolveName(resolvedName.toString(), nestedParameter, webRequest);if (arg == null) {if (namedValueInfo.defaultValue != null) {arg = resolveEmbeddedValuesAndExpressions(namedValueInfo.defaultValue);}else if (namedValueInfo.required && !nestedParameter.isOptional()) {handleMissingValue(namedValueInfo.name, nestedParameter, webRequest);}arg = handleNullValue(namedValueInfo.name, arg, nestedParameter.getNestedParameterType());}else if ("".equals(arg) && namedValueInfo.defaultValue != null) {arg = resolveEmbeddedValuesAndExpressions(namedValueInfo.defaultValue);}if (binderFactory != null) {WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);try {arg = binder.convertIfNecessary(arg, parameter.getParameterType(), parameter);}catch (ConversionNotSupportedException ex) {throw new MethodArgumentConversionNotSupportedException(arg, ex.getRequiredType(),namedValueInfo.name, parameter, ex.getCause());}catch (TypeMismatchException ex) {throw new MethodArgumentTypeMismatchException(arg, ex.getRequiredType(),namedValueInfo.name, parameter, ex.getCause());}// Check for null value after conversion of incoming argument valueif (arg == null && namedValueInfo.defaultValue == null &&namedValueInfo.required && !nestedParameter.isOptional()) {handleMissingValueAfterConversion(namedValueInfo.name, nestedParameter, webRequest);}}handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest);return arg;}

@RequestBody注解解析器会调用valid逻辑，详见org.springframework.web.method.annotation.ModelAttributeMethodProcessor#validateIfApplicable

protected void validateValueIfApplicable(WebDataBinder binder, MethodParameter parameter,Class<?> targetType, String fieldName, @Nullable Object value) {for (Annotation ann : parameter.getParameterAnnotations()) {Object[] validationHints = ValidationAnnotationUtils.determineValidationHints(ann);if (validationHints != null) {for (Validator validator : binder.getValidators()) {if (validator instanceof SmartValidator) {try {((SmartValidator) validator).validateValue(targetType, fieldName, value,binder.getBindingResult(), validationHints);}catch (IllegalArgumentException ex) {// No corresponding field on the target class...}}}break;}}}

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解决方案：

Spring解析参数的逻辑没办法调整，只能在方法调用时进行更改。

如果要在方法层面使用valid注解，就需要添加一个bean：org.springframework.validation.beanvalidation.MethodValidationPostProcessor

@Configuration
@EnableAutoConfiguration
public class ConfigurationFactory {@Beanpublic MethodValidationPostProcessor methodValidationPostProcessor(){return new MethodValidationPostProcessor();}}

然后再添加一个全局异常捕获就好了。

@Slf4j
@RestControllerAdvice
public class GlobalException {@ResponseStatus(HttpStatus.BAD_REQUEST)@ExceptionHandler({HandlerMethodValidationException.class})public Result handlerMethodValidationException(HandlerMethodValidationException e) {// 判断异常中是否有错误信息，如果存在就使用异常中的消息，否则使用默认消息if (!StringUtils.isEmpty(e.getMessage())) {return ResultUtil.failureMsg(e.getMessage());}return ResultUtil.failure(ResultEnum.SERVICE_FAILURE);}
}