[bv-dev] Feature Suggestion :: Implicit constraints

[Richard Fanning]

Hi guys,

Thanks for the responses. You’re probably both correct in that this is an uncommon use case..

Another scenario in our company where we thought this feature might be useful was again around the area of defaults. So for example a String property on an @Entity would not need to define any @Size but a sensible default (255) would apply akin to JPA providers [1]

But we’d still like to get ConstraintViolations during validation phase rather than some JPA/DB errors complaining about the strings length.

Anywho using the programmatic HV API is certainly a better approach than “hacking my into the guts of HV” albeit they pretty well organized guts ☺

I guess a take away for the Bean Validations EG might be that the HV programmatic constraints API has it’s uses and would be useful as part of JSR SPEC.

Thanks for your time.

Rich

[1] http://stackoverflow.com/questions/7509769/how-to-increase-length-of-a-string-in-mysql-while-mapping-using-jpa


From: beanvalidation-dev-bounces at lists.jboss.org [mailto:beanvalidation-dev-bounces at lists.jboss.org] On Behalf Of Gunnar Morling
Sent: 29 July 2014 14:53
To: beanvalidation-dev List
Subject: Re: [bv-dev] Feature Suggestion :: Implicit constraints

Hi,

2014-07-29 15:31 GMT+02:00 Richard Fanning <Richard.Fanning at fineos.com<mailto:Richard.Fanning at fineos.com>>:
Hi there,

We are starting to use bean validation in our product and something we would like to do is what I’ve coined as “implicit constraints”. I’d like to run this by the mailing list and get your thoughts on this as a potential feature in the spec.

The use case we have is we have a “DateTime” object which represents Date & Time. Our DateTime object pre-dates JDK 8 (and JodaTime).  A DateTime for us has some constraints

1.       The DateTime cannot me before LOW_DATE --> 01-01-1970 00:00:00
2.       The DateTime cannot me after HIGH_DATE --> 31-12-2150 23:59:59

Not sure of the exact history of these constraints but it would seem like we are trying to invent a new y2k ☺

These constraints were enforced prior to our usage of Bean Validation as these were burnt into the setter of generated POJO’s (domain objects) but now that we are moving from generated domain objects to JPA style POJO’s we’d like to use Bean Validation to apply the same constraints.
Assume we have an object which has a DateTime property as shown below

public class TestObject {

        private DateTime myDateTime;

        public DateTime getMyDateTime() {
                return myDateTime;
        }

        public void setMyDateTime(DateTime myDateTime) {
                this.myDateTime = myDateTime;
        }

}

We’d like if developers did not need to add an annotation all DateTime properties to constrain with the implicit constraints.. i.e.

@Date
private DateTime myDateTime;

In our opinion this annotation serves no additional purpose and would be an extra onus on the developer to add this so they ensure the value meets internal DateTime criteria.

Looking at the 1.1 spec I cannot see any way of applying constraints without annotating (well you can use HV XML but that would need to be done for all fields).. Is that correct.

Yes, the spec defines constraint declaration via annotations and XML. Hibernate Validator in addition has a (public) API for programmatic constraint declaration.

I’ve managed to implement “implicit constraints” by using non-standard Hibernate Validator API’s (i.e. using reflection I added an additional MetaDataProvider which added ConstrainedElements ( to the BeanConfiguration)). I can share this on GitHub is anyone is interested in taking a look.

You should better use the HV constraint API for this [1]. You could inspect your beans using reflection and define a @Date constraint for each DateTime property you find. MetaDataProvider et al. are internal APIs which may change without notice between releases.

Standardizing this API might be a useful addition as it allows to implement cases as yours in a portable manner. Not sure whether the spec should explicitly support this requirement, as it may be very specific.

Appreciate any feedback you might have.

Thanks

Rich

--Gunnar

[1] http://docs.jboss.org/hibernate/validator/5.1/reference/en-US/html_single/#section-programmatic-api




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