Records -- Using them as JPA entities and validating them with Bean Validation

[Brian Goetz]

>
>     Does JPA rely on runtime-generated proxies?  If so, what does the
>     proxy inject into the class?  (In any case, for proxies, finality
>     is a problem.)
>
>
> Yes, indeed proxies are used in some cases. E.g. when an entity is 
> configured to lazy-load specific properties, JPA would return a proxy 
> for the entity, which contains the logic to lazily fetch the property 
> value upon first invocation of someEntity.someLazyProp().

This is the high-order bit; if we can't address this then the rest don't 
matter.  Are there concrete criteria that we can use to reason about 
when it would try to create a proxy?  What if the domain class is final?

> For JPA, some control would be needed to decide between field or 
> getter (the location of the @Id annotation determines the default 
> access strategy to be used by the JPA provider, and a user may wish to 
> use one or the other).

Its pretty important that there be no control knobs.  (The first is the 
most dangerous; once you have one, you will soon have many.)

>
>       The only justifiable path I can envision would be to map to all
>     of them that would be permitted by the @Target of the annotation,
>     which might or might not work for your cases.
>
>
> That wouldn't really work well for the JPA use case, as we'd end up 
> with the annotations on fields *and* getters, which is at least 
> confusing (not sure out of my head whether it's not even considered 
> illegal).

I have to assume that if a framework sees it on both, it will (or can) 
make a choice about which it finds preferable?

> One more thing I'm realizing now is that the proposal is to name 
> generated read accessors fieldName() instead of getFieldName(). The 
> latter is expected by JPA (currently at least, it might evolve of course).

Surely this could evolve.

> So overall, as things stand, it appears to me as if it wouldn't really 
> be beneficial to use records as JPA entities.
>

I think the finality is the real question here -- so let's discuss that.