apply a UserType or CompositeUserType via a custom annotation

[gavinking]

I noticed when working on the @TimeZoneStorage stuff that even though the OffsetDateTimeCompositeUserType and ZonedDateTimeCompositeUserType are just bog-standard user types, the had to be hardwired directly into the binding logic in a not-very-elegant way, because we have no way to say stuff like:

@CompositeCustomType(userType=TimeZoneStorageCompositeUserType.class)
public @interface TimeZoneStorage {
    TimeZoneStorageType value();
}

and then have the TimeZoneStorage annotation passed to the constructor of TimeZoneStorageCompositeUserType. (Actually that would not be quite enough here, TimeZoneStorageCompositeUserType would need a way to inspect other annotations of the property.

I think this is an excellent use case to drive the design of such a facility, since it's both (a) of practical use and (b) quite nontrivial.

This is of course, all well in-line with how we're handling generators and some other things in 6.

By the way, I see that we have a @CompositeTypeRegistration annotation, but we don't appear to have a matching annotation for registering plain UserTypes. At least I could not find one, did I miss it somehow?

[gavinking]

we don't appear to have a matching annotation for registering plain UserTypes.

I added one today.

[gavinking]

See https://hibernate.atlassian.net/browse/HHH-15926.

Most of this was actually already there.

[gavinking]

Note that just allowing @Type to be applied as a meta-annotation isn't the full extent of what I propose here, since it doesn't allow the UserType to receive parameters from the annotation type.

But it's a pretty good start, and required almost no work.