Springboot2.x中的hibernate-validator（2）POST请求

清疚 2023-07-17 02:41 22阅读 0赞

### 1、ConstraintViolationException与MethodArgumentNotValidException ###

一般情况下我们会发现对GET请求的入参做参数校验时抛出ConstraintViolationException异常，而对POST请求的RequestBody做参数校验时会抛出MethodArgumentNotValidException异常。这与Spring中绑定GET参数和POST参数的方式不同有关。

### 2、MethodArgumentNotValidException异常的来源 ###

Post绑定参数依靠WebDataBinder来实现将参数绑定到JavaBean对象上。  
RequestResponseBodyMethodProcessor中的resolveArgument会将MethodParameter转换为controller中定义的JavaBean。

@Override
    	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
    			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception { 
    
    		parameter = parameter.nestedIfOptional();
    		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) { 
    				validateIfApplicable(binder, parameter);
    				if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) { 
    					throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
    				}
    			}
    			if (mavContainer != null) { 
    				mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
    			}
    		}
    
    		return adaptArgumentIfNecessary(arg, parameter);
    	}

其中validateIfApplicable在对parameter进行校验，若binder绑定的结果中有错误，则会抛出MethodArgumentNotValidException异常。

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;
    			}
    		}
    	}

从validateIfApplicable中可以发现参数校验生效的条件是能找到@Validated注解或者其他以Valid开头的注解。这与[Springboot2.x中的hibernate-validator（1）GET请求][Springboot2.x_hibernate-validator_1_GET]中以@Validated注解为切点的方式不一样。  
binder.validate

public void validate(Object... validationHints) { 
    		Object target = getTarget();
    		Assert.state(target != null, "No target to validate");
    		BindingResult bindingResult = getBindingResult();
    		// Call each validator with the same binding result
    		for (Validator validator : getValidators()) { 
    			if (!ObjectUtils.isEmpty(validationHints) && validator instanceof SmartValidator) { 
    				((SmartValidator) validator).validate(target, bindingResult, validationHints);
    			}
    			else if (validator != null) { 
    				validator.validate(target, bindingResult);
    			}
    		}
    	}

进入ValidatorImpl之后就与[Springboot2.x中的hibernate-validator（1）GET请求][Springboot2.x_hibernate-validator_1_GET]类似了。  
剩下需要探讨的问题就是这两个所使用的validator是同一个吗？

[Springboot2.x_hibernate-validator_1_GET]: https://blog.csdn.net/weixin_36142042/article/details/104949871