Spring Validation方法实现原理分析

Spring Validation方法实现原理分析

最近要做动态数据的提交处理，即需要分析提交数据字段定义信息后才能明确对应的具体字段类型，进而做数据类型转换和字段有效性校验，然后做业务处理后提交数据库，自己开发一套校验逻辑的话周期太长，因此分析了Spring Validation的实现原理，复用了其底层花样繁多的Validator，在此将分析Spring Validation原理的过程记录下，不深入细节

如何使用Spring Validation

Spring Bean初始化时校验Bean是否符合jsR-303规范

1、手动添加BeanValidationPostProcessor Bean

2、在model类中定义校验规则，如@Max、@Min、@NotEmpty

3、声明Bean，综合代码如下：

@Bean

public BeanPostProcessor beanValidationPostProcessor() {

return new BeanValidationPostProcessor();

}

@Bean

public UserModel getUserModel() {

UserModel userModel = new UserModel();

userModel.setUsername(null);

userModel.setPassword("123");

return ushttp://erModel;

}

@Data

class UserModel {

@NotNull(message = "username can not be null")

@Pattern(regexp = "[a-zA-Z0-9_]{5,10}", message = "username is illegal")

private String username;

@Size(min = 5, max = 10, message = "password's length is illegal")

private String password;

}

4、BeanValidationPostProcessor Bean内部有个boolean类型的属性afterInitialization，默认是false，如果是false，在postProcessBeforeInitialization过程中对bean进行验证，否则在postProcessAfterInitialization过程对bean进行验证

5、此种校验使用了spring的BeanPostProcessor逻辑

6、校验底层调用了doValidate方法，进一步调用validator.validate，默认validator为HibernateValidator，validation-api包为java规范，Spring默认的规范实现为hibernate-validator包，此hibernate非ORM框架Hibernate

protected void doValidate(Object bean) {

Assert.state(this.validator != null, "No Validator set");

Set> result = this.validator.validate(bean);

7、HibernateValidator默认调用ValidatorFactoryImpl来生成validator，后面展开将ValidatorFactoryImpl

支持方法级别的JSR-303规范

1、手动添加MethodValidationPostProcessor Bean

2、类上加上@Validated注解（也支持自定义注解，创建MethodValidationPostProcessor Bean时传入）

3、在方法的参数中加上验证注解，比如@Max、@Min、@NotEmpty、@NotNull等，如

@Component

@Validated

public class BeanForMethodValidation {

public void validate(@NotEmpty String name, @Min(10) int age) {

System.out.println("validate, name: " + name + ", age: " + age);

}

}

4、MethodValidationPostProcessor内部使用aop完成对方法的调用

public void afterPropertiesSet() {

Pointcut pointcut = new `AnnotationMatchingPointcut`(this.validatedAnnotationType, true);

this.advisor = new `DefaultPointcutAdvisor`(pointcut, createMethodValidationAdvice(this.validator));

}

protected Advice createMethodValidationAdvice(@Nullable Validator validator) {

return (validator != null ? new `MethodValidationInterceptor`(validator) : new MethodValidationInterceptor());

}

5、底层同样默认调用ValidatorFactoryImpl来生成validator，由validator完成校验

直接编码调用校验逻辑，如

public class Person {

@NotNull(message = "性别不能为空")

private Gender gender;

@Min(10)

private Integer age;

...

}

ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();

Validator validator = validatorFactory.getValidator();

Person person = new Person();

person.setGender(Gender.Man);

validator.validate(person);

同上，默认调用ValidatorFactoryImpl来生成validator，由validator完成具体校验

在Spring controller方法参数中使用valid或validated注解标注待校验参数

1、先熟悉下Spring的请求调用流程

2、可以看到在各种resolver处理请求参数的过程中做了参数校验

3、底层统一调用了DataBinder的validate方法

4、DataBinder的作用：Binder that allows for setting property values onto a target object, including support for validation and binding result analysis，也就是binder处理了request提交的字符串形式的参数，将其转换成服务端真正需要的类型，binder提供了对validation的支持，可以存放校验结果

5、DataBinder的validator默认在ConfigurableWebBindingInitializer中初始化，默认使用OptionalValidatorFactoryBean，该Bean继承了LocalValidatorFactoryBean，LocalValidatorFactoryBean组合了ValidatorFactory、自定义校验属性等各种校验会用到的信息，默认使用ValidatorFactoryImpl来获取validator

至此，所有的线索都指向了ValidatorFactoryImpl，下面分析下该类

public Validator `getValidator`() {

return `createValidator`(

constraintValidatorManager.getDefaultConstraintValidatorFactory(),

valueExtractorManager,

validatorFactoryScopedContext,

methodValidationConfiguration

);

}

Validator `createValidator`(ConstraintValidatorFactory constraintValidatorFactory,

ValueExtractorManager valueExtractorManager,

ValidatorFactoryScopedContext validatorFactoryScopedContext,

MethodValidationConfiguration methodValidationConfiguration) {

BeanMetaDataManager beanMetaDataManager = beanMetaDataManagers.computeIfAbsent(

new BeanMetaDataManagerKey( validatorFactoryScopedContext.getParameterNameProvider(), valueExtractorManager, qGZNuqmkmethodValidationConfiguration ),

key -> new BeanMetaDataManager(

`constraintHelper`,

executableHelper,

typeResolutionHelper,

validatorFactoryScopedContext.getParameterNameProvider(),

valueExtractorManager,

validationOrderGenerator,

buildDataProviders(),

methodValidationConfiguration

)

);

return `new ValidatorImpl`(

constraintValidatorFactory,

beanMetaDataManager,

valueExtractorManager,

constraintValidatorManager,

validationOrderGenerator,

validatorFactoryScopedContext

);

}

public final Set> validate(T object, Class>... groups) {

Contracts.assertNotNull( object, MESSAGES.validatedObjectMustNotBeNull() );

sanityCheckGroups( groups );

ValidationContext validationContext = `getValidationContextBuilder().forValidate( object )`;

if ( !validationContext.getRootBeanMetaData().hasConstraints() ) {

return Collections.emptySet();

}

ValidationOrder validationOrder = determineGroupValidationOrder( groups );

ValueContext, Object> valueContext = `ValueContext.getLocalExecutionContext`(

validatorScopedContext.getParameterNameProvider(),

object,

validationContext.getRootBeanMetaData(),

PathImpl.createRootPath()

);

return validateInContext( validationContext, valueContext, validationOrder );

}

1、getValidator->createValidator->ValidatorImpl->validate

在执行过程中封装了beanMetaDataManager、validationContext、valueContext等内容，都是校验时会用到的上下文信息，如待校验bean的所有校验项（含父类和接口）、property、method parameter的校验信息，从ValidatorFactoryScopedContext继承过来的validator通用的各种工具类（如message、script等的处理）等，内容比较复杂

2、分组（group）校验忽略，来到默认分组处理validateConstraintsForDefaultGroup->validateConstraintsForSingleDefaultGroupElement->validateMetaConstraint(注：metaConstraints维护了该bean类型及其父类、接口的所有校验，需要遍历调用validateMetaConstraint)

3、继续调用MetaConstraint的doValidateConstraint方法，根据不同的annotation type走不同的ConstraintTree

public static ConstraintTree of(ConstraintDescriptorImpl composingDescriptor, Type validatedValueType) {

if ( composingDescriptor.getComposingConstraintImpls().isEmpty() ) {

return new SimpleConstraintTree<>( composingDescriptor, validatedValueType );

}

else {

return new ComposingConstraintTree<>( composingDescriptor, validatedValueType );

}

}

4、具体哪些走simple，哪些走composing暂且不管，因为二者都调用了ConstraintTree的'getInitializedConstraintValidator'方法，该步用来获取校验annotation（如DecimalMax、NotEmpty等）对应的validator并初始化validator

5、 ConstraintHelper 类维护了所有builtin的validator，并根据校验annotation（如DecimalMax）分类，validator的描述类中维护了该validator的泛型模板（如BigDecimal），如下：

putConstraints( tmpConstraints, DecimalMax.class, Arrays.asList(

DecimalMaxValidatorForBigDecimal.class,

DecimalMaxValidatorForBigInteger.class,

DecimalMaxValidatorForDouble.class,

DecimalMaxValidatorForFloat.class,

DecimalMaxValidatorForLong.class,

DecimalMaxValidatorForNumber.class,

DecimalMaxValidatorForCharSequence.class,

DecimalMaxValidatorForMonetaryAmount.class

) );

在获取具体bean类的validator时，先根据annotation获取所有的validator，对应方法是ConstraintManager.findMatchingValidatorDescriptor，然后根据被校验对象的类型获取唯一的validator

6、然后根据上下文信息initializeValidator，进而调用validator的isValid方法校验

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