Refine customization of `EntityInformation`

[JonasProgrammer]

Hi,
I currently have the problem of marking an entity as new, even though it has a non-null UUID as id. The basic idea is to use a null-object pattern with the special case of a new UUID(0, 0), rather handling Nullability.

Reading around spring-projects/spring-data-relational#1587 either Persistable or providing a custom EntityInformation is suggested. For my use-case, Persistable has the downside of clashing with data class definitions in Kotlin having a id member, which clashes with the getId function (though it does not satisfy the interface somehow...).

EDIT: Forgot to mention I am using Spring Boot 3.4.4, which, as far as I can tell, matches the version of spring-data-relation, spring-data-r2dbc, and the common shared stuff.

So I tried to go down the road of supplementing a R2dbcRepositoryFactoryBean with getEntityInformation overridden to return a delegate of the super call, overriding isNew to my liking. The factory bean does get instantiated once per repository, but the getEntityInformation method never gets called (both verified using breakpoints in the debugger). Returning a delegating subclass of R2dbcRepositoryFactory with a similar approach to its getEntityInformation method yielded the same result.

So when one would want to go down the rabbit hole of providing a custom implementation for EntityInformation, how does one actually do this properly?

Kind regards

--
Aside from that, as a meta question: We have the null/0-default hardcoded logic, Persistable as an intrusive way of doing things, and (presumably) EntityInformation working very low-level. Is there a specific reason, why something in between is unfeasable? I saw a EntityIsNewStrategy with implementations for the hardcoded null/0, and the persistable logic.
One could give the user the ability to supply something akin as beans. And while I get not going through a chain as in web filters, for example, for performance reasons, one could choose the best matching implementation from an ordered list, where each participant could implement a boolean supports(Class<?> domainType) or something.

[JonasProgrammer]

So I have found the root cause: Subclassing R2dbcRepositoryFactory was the actual culprit.

getTargetRepository calls a private version of getEntityInformation with an additional (albeit unused) argument. Its own override of the public getEntityInformation delegates there, but there is no chance of actually overriding the behavior at this point.

My current workaround is to just override getTargetRepository instead, copying the implementation from the base-class and keeping a copy of the private fields myself from the constructor. This works so far, although I am not too happy with relying on copied code doing reflection magic, as the constructor signature may change at any notice.

So far, the actual issue is solved for me with a somewhat ugly workaround. Given the other issues regarding the new entity detection, perhaps some middle-ground between hard-coded, Persistable, or RepoBeanFactory magic would still be nice. Or at least have the default implementation play nice with customization points, so subclassing to achieve the behavior in a more reliant way is possible.

I will leave this one open for now, as I am not really sure wether the way stuff currently works is intuitive. If the discussion is better suited elswhere, just close this please.

[mp911de]

EntityInformation is an abstraction used for repositories ultimately delegating to PersistentEntity and for the is-new case, using PersistentEntity.isNew(…). Because of this arrangement, we don't really want to allow custom implementations of EntityInformation, however, it isn't great that we have potentially two variants of EntityInformation when the protected method is overridden.

In any case, that is a general theme across all of our Spring Data modules and that issue needs to be solved at the level of Spring Data Commons.

I think you could provide a subclassed MappingContext with a specific RelationalPersistentEntity delegate variant that customizes the isNew(Object) method for the specific entity type.