SpringBoot @Validated原理解析

文章目录

一、开发使用`@Validated` 出现问题
- 1.1 代码
- 1.2 请求
- 1.3 响应
二、源码：
- RequestResponseBodyMethodProcessor.resolveArgument()
- ConstraintTree#validateSingleConstraint
- InvocableHandlerMethod.getMethodArgumentValues()
- ErrorsMethodArgumentResolver.resolveArgument

一、开发使用`@Validated` 出现问题

开发过程中遇到一个问题：通过@RequestBody发送post请求的接口，接收参数为 TOUserAppModifyAddrReq,TOUserAppModifyAddrReq 有一个父类ToModifyAddrReq，调用接口时报错``

1.1 代码

引入依赖：

后边代码分析中会用到其中依赖传递的hibernate-validator-5.3.6.Final.jar，参数校验逻辑在其中。

<!-- spring-boot web依赖 -->
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><exclusions><exclusion><artifactId>jackson-databind</artifactId><groupId>com.fasterxml.jackson.core</groupId></exclusion></exclusions>
</dependency>

TOUserAppModifyAddrReq.java

public class ToUserAppModifyAddrReq extends ToModifyAddrReq{@NotNull(message="订单号不能为空z")private  String escOrderId;@NotNull(message="申请类型不能为空")private  String applyType;@NotNull(message="购买人ID不能为空")private  String buyerOnlyId;public String getBuyerOnlyId() {return buyerOnlyId;}public void setBuyerOnlyId(String buyerOnlyId) {this.buyerOnlyId = buyerOnlyId;}public String getEscOrderId() {return escOrderId;}public void setEscOrderId(String escOrderId) {this.escOrderId = escOrderId;}public String getApplyType() {return applyType;}public void setApplyType(String applyType) {this.applyType = applyType;}
}

ToModifyAddrReq.java

public class ToModifyAddrReq {@NotNull(message = "订单号不能为空f")private  String escOrderId;private  String applyType;private  String sellerOnlyId;public String getSellerOnlyId() {return sellerOnlyId;}public void setSellerOnlyId(String sellerOnlyId) {this.sellerOnlyId = sellerOnlyId;}public String getEscOrderId() {return escOrderId;}public void setEscOrderId(String escOrderId) {this.escOrderId = escOrderId;}public String getApplyType() {return applyType;}public void setApplyType(String applyType) {this.applyType = applyType;}
}

Controller 代码如下：

这里使用@Validated 校验入参，@RequestBody

@ResponseBody
@RequestMapping("/toUserModifyAddressPage")
public ReturnData toUserModifyAddressPage(@Validated @RequestBody RequestData<ToUserAppModifyAddrReq> req, BindingResult bindingResult){……if(bindingResult.hasErrors()){log.warn("toMerchantModifyAddressPage illegal params:" + bindingResult.getAllErrors().get(0).getDefaultMessage());}……
}

1.2 请求

curl --location --request POST 'http://retailorder-ordersignandcancelservice.http.beta.uledns.com/orderSignAndCancelService/order/toUserModifyAddressPage.do' \
--header 'User-Agent: Apipost client Runtime/+https://www.apipost.cn/' \
--header 'Content-Type: application/json' \
--data '{"head":{"requestTime":1635924914426,"requestId":"fa774d76e52649499043204a1ecc0a01","moduleApp":"my-myShoppingOrderWeb"},"dataBody":{"applyType":"USER","escOrderId":"621073000058578405","buyerOnlyId":10000040365}
}'

1.3 响应

{"result":null,"returnCode":"0002","returnMsg":"订单号不能为空f"}

这里看到，校验成功，显示订单号不能为空f, 这里为什么出现这个错误呢？原因是，@Validated 校验中，会把参数父类中的字段escOrderId 也校验，但是父类中的escOrderId字段值为空，这里其实是代码有问题，继承写的有问题，不需要重写父类属性，修改下即可。

但具体为什么如此，我下面分析下代码，，，，

二、源码：

接口接收请求是通过 @RequestBody, spring的方法参数解析器（HandlerMethodArgumentResolver），参数校验这块肯定是在对应的方法参数解析器里执行的。如下是@RequestBody注解对应的参数解析器RequestResponseBodyMethodProcessor。

RequestResponseBodyMethodProcessor.resolveArgument()

直接定位到resolveArgument这个方法，很明显，该方法是根据参数类型找到支持的消息转换器（Message Converter），然后从request body中读取信息，最后转换成对应的参数实体。

WebDataBinder主要是完成对象属性校验的。如果你熟悉@ModelAttribute注解对应的方法参数解析器（ModelAttributeMethodProcessor），是先通过WebDataBinder进行入参属性绑定，然后再进行校验。

@Overridepublic Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {parameter = parameter.nestedIfOptional();//消息转换Object arg = readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());String name = Conventions.getVariableNameForParameter(parameter);if (binderFactory != null) {WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);if (arg != null) {//遍历参数注解validateIfApplicable(binder, parameter);//如果校验结果有异常，且目标方法中最后有Errors（BindingResult 继承 Errors）类型的参数，则抛出异常if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());}}if (mavContainer != null) {// BindingResult结果,放入 ModelAndViewContainer 对象中保存起来mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());}}return adaptArgumentIfNecessary(arg, parameter);}

简单说一下validateIfApplicable方法的逻辑，遍历当前参数methodParam所有的注解，如果注解是@Validated或注解的名字以‘Valid’开头，则使用WebDataBinder对象执行校验逻辑。

//简单说一下validateIfApplicable方法的逻辑，遍历当前参数methodParam所有的注解，
// 如果注解是@Validated或注解的名字以‘Valid’开头，则使用WebDataBinder对象执行校验逻辑。
protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {Annotation[] annotations = parameter.getParameterAnnotations();for (Annotation ann : annotations) {Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class);if (validatedAnn != null || ann.annotationType().getSimpleName().startsWith("Valid")) {Object hints = (validatedAnn != null ? validatedAnn.value() : AnnotationUtils.getValue(ann));Object[] validationHints = (hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});binder.validate(validationHints);break;}}
}

ConstraintTree#validateSingleConstraint

通过 hibernate-validator-5.3.6.Final-sources.jar 对参数进行校验，下面是部分代码

org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree#validateSingleConstraint ，判断valueContext中 currentValue中是否有值：

子类中对应的字段：

父类中对应的字段：

这里可以看出父类中的字符值为空，且父类中设置了 @NotNull 注解 ,此处就会返回到 Set<ConstraintViolation<T>> localViolations中，接着设置到 constraintViolations 中，

最后会把BindingResult结果放到ModelAndViewContainer对象中保存起来，记住BindingResult.MODEL_KEY_PREFIX这个key prefix。

BindingResult结果也已经拿到了，该怎么传递给方法呢？

请求，通过DispatcherServlet.doDispatch() ，

RequestHandlerMappingAdapter，

InvocableHandlerMethod.getMethodArgumentValues()为请求获取入参信息,

HandlerMethodArgumentResolverComposite#resolveArgument获取对应方法解析器RequestResponseBodyMethodProcessor，并解析方法参数，

InvocableHandlerMethod.getMethodArgumentValues()

这里遍历方法参数，逐个解析，当解析完@Validated @RequestBody RequestData<ToUserAppModifyAddrReq> req参数，进入参数BindingResult bindingResult的解析，

/*** Get the method argument values for the current request.*/private Object[] getMethodArgumentValues(NativeWebRequest request, ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {MethodParameter[] parameters = getMethodParameters();Object[] args = new Object[parameters.length];// 不同参数，不同的参数解析器for (int i = 0; i < parameters.length; i++) {MethodParameter parameter = parameters[i];parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);args[i] = resolveProvidedArgument(parameter, providedArgs);if (args[i] != null) {continue;}if (this.argumentResolvers.supportsParameter(parameter)) {try {args[i] = this.argumentResolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);continue;}catch (Exception ex) {if (logger.isDebugEnabled()) {logger.debug(getArgumentResolutionErrorMessage("Failed to resolve", i), ex);}throw ex;}}if (args[i] == null) {throw new IllegalStateException("Could not resolve method parameter at index " +parameter.getParameterIndex() + " in " + parameter.getMethod().toGenericString() +": " + getArgumentResolutionErrorMessage("No suitable resolver for", i));}}return args;}

通过BindingResult bindingResult参数，获取到ErrorsMethodArgumentResolver 解析器。

private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);if (result == null) {for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) {if (logger.isTraceEnabled()) {logger.trace("Testing if argument resolver [" + methodArgumentResolver + "] supports [" +parameter.getGenericParameterType() + "]");}if (methodArgumentResolver.supportsParameter(parameter)) {result = methodArgumentResolver;this.argumentResolverCache.put(parameter, result);break;}}}return result;}

ErrorsMethodArgumentResolver.resolveArgument

看到ErrorsMethodArgumentResolver这个参数解析器的注释和源码，的确是针对BindingResult这种参数类型的。BindingResult.MODEL_KEY_PREFIX这个常量在这里出现了，在ModelAndViewContainer对象中拿到BindingResult对象。注意最后面抛出了一个IllegalStateException异常，也就是在ModelAndViewContainer对象中没有找到BindingResult对象的时候才会抛出这个异常。

@Override
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {ModelMap model = mavContainer.getModel();if (model.size() > 0) {int lastIndex = model.size()-1;String lastKey = new ArrayList<String>(model.keySet()).get(lastIndex);if (lastKey.startsWith(BindingResult.MODEL_KEY_PREFIX)) {return model.get(lastKey);}}throw new IllegalStateException("An Errors/BindingResult argument is expected to be declared immediately after the model attribute, " +"the @RequestBody or the @RequestPart arguments to which they apply: " + parameter.getMethod());
}