[hibernate-dev] [SEARCH] 6.0: what if we flipped our metadata definition upside down?

[Yoann Rodiere]

Hello,

Currently, the medata definition mechanisms in Search work this way:

   - the primary way to define metadata is using annotations
   - the secondary way to define metadata is programmatic, *but it only
   instantiates annotations,* simulating annotated entities
   - classes needing to access those "low-level" metadata
   (AnnotationMetadataProvider in particular) only manipulate annotations

I'm wondering if we should change that, flipping the metadata definition
upside-down: the programmatic definition would be the main one, with a
clean, annotation-free low-level metadata model, and annotations would
merely be translated to this low-level metadata using a walker and the
programmatic API.

My first argument is that creating "simulated" annotations is rather odd,
but I'll grant you it's hardly receivable.
But I can see other, more objective reasons:

   - We periodically notice missing methods in the programmatic API ([1],
   [2], [3], [4]), because we thought "annotations first" and forgot about the
   programmatic API. If annotation processing was to rely on programmatic
   mapping, this "annotations first" thinking would not be a problem anymore,
   but rather a good thing: we would have to implement both the programmatic
   API and the annotations in order to make it work.
   - If we want to support programmatic mapping for "free-form" (i.e.
   non-POJO) entities, we will need to be more generic than what annotations
   allow at some point. We already spotted the problem of using "Class<?>" to
   denote entity types, but there may be more. For instance denoting property
   identifiers, or property types, ... It just doesn't feel future-proof to
   rely on an intrinsically Java way of modeling metadata (the annotations)
   and try to model non-Java things with it...

What do you think? Are there any objections to making the programmatic API
the primary way to define metadata? Note that I'm not talking about making
users use it in priority (it won't change anything for them), just about
making it more central in our architecture.


|1]
http://stackoverflow.com/questions/43006746/hibernate-search-5-2-programmatic-configuration-of-facet-field
[2] https://hibernate.atlassian.net/browse/HSEARCH-1764
[3] https://hibernate.atlassian.net/browse/HSEARCH-2199
[4] https://hibernate.atlassian.net/browse/HSEARCH-1079

Yoann Rodière <yoann at hibernate.org>
Hibernate NoORM Team