Nitrite/Java: [Feature Request] Mappable with MappableDeserializer?

[morrica]

Hey, great work!
Any possibility of changing Mappable.read() to use something more like the Jackson JsonDeserializer instead of the current design?

Right now it is difficult or impossible to use with entities that include final fields. The change would allow us to handle entity initialization through an existing constructor.

One possibility would be to replace void read(NitriteMapper, Document) with a @Deserializer annotation on the Mappable entity that gives you the MappableDeserializer implementation to use. Then have the MappableDeserializer<T> interface include T deserialize(NitriteMapper, Document);. I believe this would allow you to deserialize entities without having to create an instance of them first.

[anidotnet]

The whole point of using Mappable interface is to avoid serialization and de-serialization overhead in db operations and that also includes instantiating objects via reflection. If you want fine grained de-serialization, we have Jackson module for that. If you have simple entity, use Mappable, otherwise fall back to Jackson serialization.

[morrica]

I see what you're saying. I think the real issue I am trying to work around is the need to create empty entities during repository creation. It is playing havoc with entities with @Nonnull final fields and generally leads to NullPointerExceptions during repository creation on entity fields that should never be null. The JacksonMapper doesn't help with this even though the entities can be serialized/deserialized by Jackson just fine. Ultimately I think this issue is deeper than the Mappable implementation.

However, if you wanted an efficient Mappable without having to use reflection that could be done by caching the MappableDeserializer for each type. That way the only use of reflection is on the initial Class.getAnnotation(Deserializer.class) call. However, I acknowledge that while it increases flexibility of the Mappable interface for use with final fields it doesn't actually solve my ultimate problem.