详述Spring对Bean Validation支持的核心API：Validator、SmartValidator、LocalValidatorFactoryBean...【享学Spring】（中）

public class CustomValidatorBean extends SpringValidatorAdapter implements Validator, InitializingBean {
  // javax.validation.ValidatorFactory
  @Nullable
  private ValidatorFactory validatorFactory;
  @Nullable
  private MessageInterpolator messageInterpolator;
  @Nullable
  private TraversableResolver traversableResolver;
  ... // 省略所有set方法（木有get方法）
  // 默认设置~~~~初始化
  @Override
  public void afterPropertiesSet() {
    if (this.validatorFactory == null) {
      this.validatorFactory = Validation.buildDefaultValidatorFactory();
    }
    // 这一句就是new ValidatorContextImpl( this )
    ValidatorContext validatorContext = this.validatorFactory.usingContext();
    // 插值器
    MessageInterpolator targetInterpolator = this.messageInterpolator;
    if (targetInterpolator == null) {
      targetInterpolator = this.validatorFactory.getMessageInterpolator();
    }
    validatorContext.messageInterpolator(new LocaleContextMessageInterpolator(targetInterpolator));
    if (this.traversableResolver != null) {
      validatorContext.traversableResolver(this.traversableResolver);
    }
    // 把已经配置好的这个Validator设置进去~
    setTargetValidator(validatorContext.getValidator());
  }
}

// @since 3.0  这个类非常的丰富  实现了接口javax.validation.ValidatorFactory
// 实现了ApplicationContextAware拿到Spring上下文...
// 但其实，它的实际工作都是委托式，自己只提供了各式各样的配置~~~（主要是配置JSR）
public class LocalValidatorFactoryBean extends SpringValidatorAdapter implements ValidatorFactory, ApplicationContextAware, InitializingBean, DisposableBean {
  ... // 省略所有的配置属性
  ... // 省略所有的get/set
  ... // 省略afterPropertiesSet()进行的默认配置初始化  最终调用setTargetValidator(this.validatorFactory.getValidator());
  // 备注：还记得上文吗？上文的validator校验器是从上下文拿的，这里是从工厂拿的
  // 省略所有对ValidatorFactory接口的方法实现~
}

// @since 4.0.1
public class OptionalValidatorFactoryBean extends LocalValidatorFactoryBean {
  @Override
  public void afterPropertiesSet() {
    try {
      super.afterPropertiesSet();
    } catch (ValidationException ex) {
      LogFactory.getLog(getClass()).debug("Failed to set up a Bean Validation provider", ex);
    }
  }
}

public class SpringConstraintValidatorFactory implements ConstraintValidatorFactory {
  private final AutowireCapableBeanFactory beanFactory;
  public SpringConstraintValidatorFactory(AutowireCapableBeanFactory beanFactory) {
    Assert.notNull(beanFactory, "BeanFactory must not be null");
    this.beanFactory = beanFactory;
  }
  // 注意：此处是直接调用了create方法，放进容器
  @Override
  public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key) {
    return this.beanFactory.createBean(key);
  }
  // Bean Validation 1.1 releaseInstance method
  public void releaseInstance(ConstraintValidator<?, ?> instance) {
    this.beanFactory.destroyBean(instance);
  }
}

public class MessageSourceResourceBundleLocator implements ResourceBundleLocator {
  private final MessageSource messageSource;
  public MessageSourceResourceBundleLocator(MessageSource messageSource) {
    Assert.notNull(messageSource, "MessageSource must not be null");
    this.messageSource = messageSource;
  }
  @Override
  public ResourceBundle getResourceBundle(Locale locale) {
    return new MessageSourceResourceBundle(this.messageSource, locale);
  }
}

//@since 27.02.2003 java.util.ResourceBundle  它是JDK提供来读取国际化的属性配置文件的  是个抽象类
public class MessageSourceResourceBundle extends ResourceBundle {
  private final MessageSource messageSource;
  private final Locale locale;
  public MessageSourceResourceBundle(MessageSource source, Locale locale) {
    Assert.notNull(source, "MessageSource must not be null");
    this.messageSource = source;
    this.locale = locale;
  }
  public MessageSourceResourceBundle(MessageSource source, Locale locale, ResourceBundle parent) {
    this(source, locale);
    setParent(parent);
  }
  @Override
  @Nullable
  protected Object handleGetObject(String key) {
    try {
      return this.messageSource.getMessage(key, null, this.locale);
    } catch (NoSuchMessageException ex) {
      return null;
    }
  }
  // @since 1.6
  @Override
  public boolean containsKey(String key) {
    try {
      this.messageSource.getMessage(key, null, this.locale);
      return true;
    }
    catch (NoSuchMessageException ex) {
      return false;
    }
  }
  @Override
  public Enumeration<String> getKeys() {
    throw new UnsupportedOperationException("MessageSourceResourceBundle does not support enumerating its keys");
  }
  @Override
  public Locale getLocale() {
    return this.locale;
  }
}