fallback id generator

[gavinking]

It would be very convenient to be able to specify a "fallback" id generator to use when @GeneratedValue has no generator member, and the entity does not explicitly declare any @TableGenerator or @SequenceGenerator. This fallback could even be per-GenerationType.

One way would be via a property setting, so that, for example, you could set:

jakarta.persistence.generator.AUTO = myDefaultSequenceGenerator
jakarta.persistence.generator.SEQUENCE = myDefaultSequenceGenerator
jakarta.persistence.generator.TABLE = myDefaultTableGenerator

But actually the most natural solution would be to let you declare a @TableGenerator or @SequenceGenerator with no name at the package level. And then that generator would be used as the fallback for the whole package.

That's a great solution, but I believe @lukasj mentioned he has some problems with us using package-level annotations.

[lukasj]

those "problems" are mostly relate to the build tool(s) being used:

• maven 3.6.0-3.6.2 was somehow ignoring package-info files as such causing issues running xjc/jaxb etc (I wasn't directly involved in debugging this but noticed problems in few projects)
• maven compiler version 3.10.0 changed the way it treats package-infos (partially described in MCOMPILER-205) and that has impact on multi-release builds (package-info files are not in certain configurations by default recompiled under the other/lower release version)

OTOH I do not think we should be feeling blocked by issues in particular build tools - there are other tools having no problems with this and since Java language has package-info we should use it if it makes sense to us

[gavinking]

@lukasj OK, then in that case I would consider this one for 3.2, since it ties in with work we already did.

Actually, a package-level annotation would also be a super nice solution to #409, IMO.

[gavinking]

the most natural solution would be to let you declare a @TableGenerator or @SequenceGenerator with no name at the package level. And then that generator would be used as the fallback for the whole package.

If we allowed @TableGenerator and @SequenceGenerator the package level, the semantics would be:

• if name is specified, the annotation defines a single (global) generator as usual, but
• if name is defaulted, the annotation is a template which defines a generator of each entity which needs one (and its name is the name of the entity, consistently to what we defined earlier).

[gavinking]

See 6f6e593.