java - 如何在基类上使用 javax.validation (JSR303)？

Question

我想使用标准 javax.validation 进行属性验证，并使用我自己的验证进行功能验证。简化的子类如下所示:

public class TestData extends AbstractData {
  @NotNull
  Long id = null;

  @NotNull
  Long value = null;

  public Set<ConstraintViolation<TestData>> validateFunctional() {
    Set<ConstraintViolation<TestData>> violations = new HashSet<>();
    if ( id < 42 || value > 4711 ) {
      //--- here comes another question: how do I create a constraint violation?
     }
     return violations;
  }
}

这是基类:

public abstract class AbstractData {
  public Set<ConstraintViolation<?>> validate() {
    //--- First validate single properties
    Set<ConstraintViolation<?>> violations = validator.validate( this );
  }
  //--- Single props OK => validate functional
  if ( violations.isEmpty()) {
     violations.add( validateFunctional());
  }
  return violations;
}

报错

Type mismatch: cannot convert from Set<ConstraintViolation<AbstractData>> to Set<ConstraintViolation<?>>

Answer 1

我相信这应该是您正在寻找的:

public abstract class AbstractData<T> {

  abstract T getObj();

  public Set<ConstraintViolation<T>> isValid(){
    //do your custom validations if needed
    return Validation.buildDefaultValidatorFactory()
            .getValidator().validate(getObj());
  }
}

要验证的 POJO:

public class Bar extends AbstractData<Bar> {
    @NotNull
    private Long id;

    @NotNull
    private Long value;

    @CustomConstraint
    private Long customConstraint;

    @Override
    public Bar getObj() {
        return this;
    }
}

然后只需调用bar.isValid()即可。

编辑:

关于您关于自定义约束的问题，您可以这样做:

@Constraint(validatedBy = {CustomConstraint.CustomConstraintValidator.class})
@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(value = RetentionPolicy.RUNTIME)
@Documented
public @interface CustomConstraint {

    String message() default "Invalid value";

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

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

    class CustomConstraintValidator implements ConstraintValidator<CustomConstraint, Long> {

        @Override
        public void initialize(CustomConstraint customConstraint) {

        }

        @Override
        public boolean isValid(Long obj, ConstraintValidatorContext constraintValidatorContext) {
            if (obj == null)
                return false;

            if (obj < 10)
                return false;

            return true;
        }
    }
}

在此示例中，如果我使用 @CustomConstraint 注释 Long 字段并传递小于 10 或 null 的值， validator 将返回错误，否则不会返回错误。验证本身在示例中毫无用处，我只是提供了一些内容作为片段供您构建自己的验证。