So the way all underlieing communication is done is through a protobuf. So in python I know they hijack the expression and they can then construct the protobuf from the passed in python lambda. In Java land we can't really do that since lambdas are desugared at compile time to just be functions. In Java I can't even overload operators like you can in Scala or C++ to make it a little nicer. The result is your pretty much left with rolling the protobuf by hand.
The upcoming 1.13 release will introduce a pure JSON interface for queries (which official drivers will switch to). You'll be able to construct JSON directly, and send it to the server -- no protobufs. Would that make things easier?
It will make it on par with the interface for other document oriented databases. I think it will be a lot more user friendly then the protobuf, and it might be the best that Java can do.
To clarify, in 1.13 JSON will be a communication protocol for queries. It's not intended to be used by the end user, but by the client drivers. You can use it as an end user, but it isn't nearly as nice as native language drivers.
The change is meant to simplify driver development, packaging, and improve performance. Protobuf is worse than JSON in almost all of these categories.
You may be able to utilize a lot of their code for converting the lambda bytecode.. or not. Anyway it's interesting to see how they're dealing with the problem you've run into.
