typesafe references to named queries and result set mappings

[gavinking]

We should enhance the jpamodelgen to produce things that can be used as typesafe references to @NamedQuerys and @ResultSetMappings.

This could in principle be as simple as just a

public static final String customerByName = "customerByName";

for @NamedQuery(name="customerByName", ....) but in principle we could parse the query and determine its result type, letting us generate something like:

public static final NamedQuery<Customer> customerByName = new NamedQuery<>("customerByName");

I would be happy to work on this if someone who knows how jpamodelgen works could point me in the right direction.

[gavinking]

but in principle we could parse the query and determine its result type

Note that for @ResultSetMapping it's even easier to determine the result type.

[beikov]

Sounds like a nice addition, but I think there are a few things to consider.

• If we want to use this NamedQuery contract we have to define it first, which would be part of hibernate-core, hence users would be required to depend on hibernate-core if they want to use that feature. We can't simply expect users to do that IMO and ergo this should be deactivated by default. How about providing static factories instead? public static TypedQuery<Customer> customerByName(EntityManager em) {...}. Heck, we could even try to parse out the parameter names and try to infer the types :)
• Another issue is, that named queries do not necessarily have to be part of an entity. In XML they are listed without entity context. So where should we put the factory method? Maybe we should emit a dedicated class that contains all named queries instead?

Anyway, you'd probably have to analyze annotations in org.hibernate.jpamodelgen.annotation.AnnotationMetaEntity to register named queries etc. and do the same in org.hibernate.jpamodelgen.xml.JpaDescriptorParser for the XML defined ones. Finally you'd have to emit the special class in org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor#createMetaModelClasses

[gavinking]

This (and much more) has been implemented.