深入了解数据校验（Bean Validation）：ValidatorFactory和Validator等核心API【享学Java】（下）

public class ValidatorImpl implements Validator, ExecutableValidator {
  private static final Collection<Class<?>> DEFAULT_GROUPS = Collections.<Class<?>>singletonList( Default.class );
  // 分组Group校验的顺序问题
  // 若依赖于校验顺序，可用使用@GroupSequence注解来控制Group顺序
  private final transient ValidationOrderGenerator validationOrderGenerator;
  private final ConstraintValidatorFactory constraintValidatorFactory;
  ...
  // 唯一构造函数~
  public ValidatorImpl(ConstraintValidatorFactory constraintValidatorFactory, BeanMetaDataManager beanMetaDataManager,
      ValueExtractorManager valueExtractorManager, ConstraintValidatorManager constraintValidatorManager,
      ValidationOrderGenerator validationOrderGenerator, ValidatorFactoryScopedContext validatorFactoryScopedContext) {
    this.constraintValidatorFactory = constraintValidatorFactory;
    this.beanMetaDataManager = beanMetaDataManager;
    this.valueExtractorManager = valueExtractorManager;
    this.constraintValidatorManager = constraintValidatorManager;
    this.validationOrderGenerator = validationOrderGenerator;
    this.validatorScopedContext = new ValidatorScopedContext( validatorFactoryScopedContext );
    this.traversableResolver = validatorFactoryScopedContext.getTraversableResolver();
    this.constraintValidatorInitializationContext = validatorFactoryScopedContext.getConstraintValidatorInitializationContext();
  }
  @Override
  public final <T> Set<ConstraintViolation<T>> validate(T object, Class<?>... groups) {
    sanityCheckGroups( groups ); // groups里面的内容不能有null
    @SuppressWarnings("unchecked")
    Class<T> rootBeanClass = (Class<T>) object.getClass();
    BeanMetaData<T> rootBeanMetaData = beanMetaDataManager.getBeanMetaData( rootBeanClass );
    // 若没有约束存在，直接返回~
    if ( !rootBeanMetaData.hasConstraints() ) {
      return Collections.emptySet();
    }
    // ValidationContext这个实体类里面的属性极其多~  持有各种组件的引用
    ValidationContext<T> validationContext = getValidationContextBuilder().forValidate( rootBeanMetaData, object );
    // 找到这个分组们的（带有顺序）
    ValidationOrder validationOrder = determineGroupValidationOrder( groups );
    // ValueContext一个实例用于收集所有相关信息，以验证单个类、属性或方法调用。
    ValueContext<?, Object> valueContext = ValueContext.getLocalExecutionContext(validatorScopedContext.getParameterNameProvider(), object,
        validationContext.getRootBeanMetaData(), PathImpl.createRootPath()
    );
    // 此方法传入的信息量非常大~~ 验证上下文、值上下文，验证器
    // 返回的是失败的消息对象：ConstraintViolation  它是被存储在ValidationContext里的~~~~
    return validateInContext( validationContext, valueContext, validationOrder );
  }
  ... // 省略validateProperty和validateValue
  // 下面实现`ExecutableValidator`的相关方法  它的四个接口方法无非就是两个方法：validateParameters和validateReturnValue 略
  //  beanMetaDataManager.getBeanMetaData( clazz )还是相对比较重要的
  @Override
  public final BeanDescriptor getConstraintsForClass(Class<?> clazz) {
    return beanMetaDataManager.getBeanMetaData( clazz ).getBeanDescriptor();
  }
  @Override
  public final <T> T unwrap(Class<T> type) {
    if ( type.isAssignableFrom( Validator.class ) ) {
      return type.cast( this );
    }
    throw LOG.getTypeNotSupportedForUnwrappingException( type );
  }
  // 返回自己即可。因为它是可以校验方法入参、返回值等等的
  @Override
  public ExecutableValidator forExecutables() {
    return this;
  }
  ... // 省略所有的私有方法们~
}