See: PR: https://github.com/mongodb/mongo-java-driver/pull/846

I would like to discuss adding something like this to the DecoderContext. This would allow me to attach a cache in Morphia so that when I'm fetching referenced documents, I can cache them and reuse the hydrated objects rather than reprocessing them all over and over. The precise shape of this API could no doubt use some fine tuning but this is the general idea.