Spring controller校验入参的方法详解
作者：有信仰
项目中使用Springboot,在Controller中配置了@NotNull和@Valid,@Notnull不生效,@Valid生效,返回http status为400,本文给大家介绍了Spring controller校验入参的方法,需要的朋友可以参考下
问题描述
项目中使用Springboot，在Controller中配置了@NotNull和@Valid，@Notnull不生效，@Valid生效，返回http status为400。
@RestController
@RequestMapping("/demo")
public class DemoController {
@Override
@PostMapping("/user")
public CreateUserRsp createUser(
@NotNull @Size(min = 1, max = 64) @RequestHeader(value = "token") String token,
@NotNull @Valid @RequestBody CreateUserReq createUserReq) {
// 业务逻辑
}
}
原因分析
controller接收到请求，首先会进行参数解析，解析相关的类：
为什么@RequestBody中的@Valid生效了？
参数中@RequestBody注解是使用RequestResponseBodyMethodProcessor解析的，下面重点看下这个。
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer, NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
parameter = parameter.nestedIfOptional();
Object arg = this.readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());
String name = Conventions.getVariableNameForParameter(parameter);
if (binderFactory != null) {
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
if (arg != null) {
// 重点
this.validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && this.isBindExceptionRequired(binder, parameter)) {
throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
}
}
if (mavContainer != null) {
mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
}
}
return this.adaptArgumentIfNecessary(arg, parameter);
}
protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {
Annotation[] annotations = parameter.getParameterAnnotations();
Annotation[] var4 = annotations;
int var5 = annotations.length;
for(int var6 = 0; var6 < var5; ++var6) {
Annotation ann = var4[var6];
// 重点，解析参数的注解
Object[] validationHints = ValidationAnnotationUtils.determineValidationHints(ann);
if (validationHints != null) {
// 执行校验
binder.validate(validationHints);
break;
}
}
}
可以看出，@Valid和@Validated注解都可以解析到：
public static Object[] determineValidationHints(Annotation ann) {
if (ann instanceof Validated) {
return ((Validated)ann).value();
} else {
Class<? extends Annotation> annotationType = ann.annotationType();
if ("javax.validation.Valid".equals(annotationType.getName())) {
return EMPTY_OBJECT_ARRAY;
} else {
Validated validatedAnn = (Validated)AnnotationUtils.getAnnotation(ann, Validated.class);
if (validatedAnn != null) {
return validatedAnn.value();
} else {
return annotationType.getSimpleName().startsWith("Valid") ? convertValidationHints(AnnotationUtils.getValue(ann)) : null;
}
}
}
}
为什么@RequestHeader中的@NotNull没有生效？
按照上面的思路，我们看下RequestHeaderMapMethodArgumentResolver，里面并没有调用validate相关的代码。
怎么样才能生效？
在类上加@Validated。并且加maven依赖
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-validation</artifactId> </dependency>
@Validated生效原理
后处理器MethodValidationPostProcessor中给使用了@Validated注解的类创建了个切面。实际执行切面逻辑的是MethodValidationInterceptor
public class MethodValidationPostProcessor extends AbstractBeanFactoryAwareAdvisingPostProcessor implements InitializingBean {
private Class<? extends Annotation> validatedAnnotationType = Validated.class;
public void afterPropertiesSet() {
Pointcut pointcut = new AnnotationMatchingPointcut(this.validatedAnnotationType, true);
this.advisor = new DefaultPointcutAdvisor(pointcut, this.createMethodValidationAdvice(this.validator));
}
protected Advice createMethodValidationAdvice(@Nullable Validator validator) {
return validator != null ? new MethodValidationInterceptor(validator) : new MethodValidationInterceptor();
}
}
请求执行时，MethodValidationInterceptor中先判断方法和类上有没有@Validated，
public Object invoke(MethodInvocation invocation) throws Throwable {
if (this.isFactoryBeanMetadataMethod(invocation.getMethod())) {
return invocation.proceed();
} else {
// 方法和类上有没有@Validated
Class<?>[] groups = this.determineValidationGroups(invocation);
ExecutableValidator execVal = this.validator.forExecutables();
Method methodToValidate = invocation.getMethod();
Object target = invocation.getThis();
Assert.state(target != null, "Target must not be null");
Set result;
try {
// 校验
result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
} catch (IllegalArgumentException var8) {
methodToValidate = BridgeMethodResolver.findBridgedMethod(ClassUtils.getMostSpecificMethod(invocation.getMethod(), target.getClass()));
result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
}
if (!result.isEmpty()) {
// 校验失败的异常
throw new ConstraintViolationException(result);
} else {
Object returnValue = invocation.proceed();
result = execVal.validateReturnValue(target, methodToValidate, returnValue, groups);
if (!result.isEmpty()) {
throw new ConstraintViolationException(result);
} else {
return returnValue;
}
}
}
}
实际校验的类是ValidatorImpl。代码一直跟下去，能找到最终执行校验的地方。---注意，ValidatorImpl已经是hibernate-validator提供的了。
private void validateMetaConstraints(BaseBeanValidationContext<?> validationContext, ValueContext<?, Object> valueContext, Object parent, Iterable<MetaConstraint<?>> constraints) {
Iterator var5 = constraints.iterator();
while(var5.hasNext()) {
MetaConstraint<?> metaConstraint = (MetaConstraint)var5.next();
this.validateMetaConstraint(validationContext, valueContext, parent, metaConstraint);
if (this.shouldFailFast(validationContext)) {
break;
}
}
}
总结
controller中requestBody中直接可以用@Valid或@Validated校验，如果想校验方法中单个参数，需要在方法或类上加@Validated，这样会开启方法校验的切面，切面中会拿到方法签名中每个字段的注解然后进行校验。
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