Hi colleagues!

I have some results of investigation. I describe my things. Any ideas welcome!
Main problem in the method "decode" of class below

public class TupleCodec implements Codec<Tuple> {
	@Override
	public Tuple decode(BsonReader reader, DecoderContext decoderContext) {
                       ...
	}
       ....
}

Problem is I don't know what type is loaded. It leads to problem with mapping between field "_id" and field with annotation @Id .
I see next ways:

1. I can prepare not fully initialized Tuple by reading BsonReader. Initialization will finished in method "getTuple" (and the like)
2. I can add new field "_type". But .... it leads to problem if json not contains the field

Any ideas or advises are welcome