如何解决 JSR-303 自定义验证器中的依赖关系答案

【问题标题】：How to resolve dependencies in JSR-303 custom validator如何解决 JSR-303 自定义验证器中的依赖关系
【发布时间】：2017-04-10 15:16:47
【问题描述】：

假设有一个像这样的自定义验证注解

@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = {ThirdPartyConstraintValidator.class}) 
@Documented
public @interface ThirdPartyConstraint {
   String message() default "Invalid";

   Class<?>[] groups() default {};

   Class<? extends Payload>[] payload() default {};
}

以及需要其他服务的相应验证器

public class ThirdPartyConstraintValidator implements ConstraintValidator<ThirdPartyConstraint, Pojo> {

  private ThirdPartyService thirdPartyService;

  @Override
  public void initialize(ThirdPartyConstraint thirdPartyConstraint) {}

  @Override
  public boolean isValid(Pojo pojo, ConstraintValidatorContext constraintValidatorContext) {
    return thirdPartyService.isValid(pojo);
  }

  public void setThirdPartyService(ThirdPartyService thirdPartyService) {
    this.thirdPartyService = thirdPartyService;
  }
}

验证上下文是用这样的 Hibernate 实现初始化的

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();

// and then some bean is validated
validator.validate(new Pojo());

在后台validate 方法调用class.newInstance() 以获取验证器实现。所以，对于ThirdPartyConstraintValidator，永远不会注入依赖ThirdPartyService。

在没有任何框架的情况下使用ValidationFactory 时，有没有办法通过setter 或构造函数将ThirdPartyService 注入ThirdPartyConstraintValidator？

更新：

在@matthias 回答之后，我更新了我的ValidatorFactory 以在其中初始化ThirdPartyConstraintValidator

public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> aClass) {
   if (ThirdPartyConstraintValidator.class.equals(aClass)) {
      ThirdPartyConstraintValidator thirdPartyConstraintValidator = new ThirdPartyConstraintValidator();
      thirdPartyConstraintValidator.setThirdPartyService(new ThirdPartyService());
      return (T) thirdPartyConstraintValidator;
   }
   return null;
}

【问题讨论】：

尝试将@Autowired添加到private ThirdPartyService thirdPartyService;
@HJz 谁说我用的是Spring？

标签： java hibernate validation bean-validation

【解决方案1】：

你可以实现一个自定义的 ConstraintValidatorFactory 来设置你的依赖。

见BeanVal Spec或Hibernate Validator Doc

Validator v = Validation.byDefaultProvider().configure()
        .constraintValidatorFactory(new MyConstraintValidatorFactory())
        .buildValidatorFactory()
        .getValidator();

class MyConstraintValidatorFactory implements ConstraintValidatorFactory {

    public <T extends ConstraintValidator<?, ?>> T getInstance(final Class<T> arg0) {
        //do your stuff to set dependencies
        ...
    }

    public void releaseInstance(final ConstraintValidator<?, ?> arg0) {
        ...
    }
}

【讨论】：