Move some of the supporting code for gRPC to spring-grpc
https://github.com/spring-projects/spring-grpc/issues/174
JsonToGrpcFilterFactory has issues that makes it harder to use (and unusable for some projects): https://github.com/spring-cloud/spring-cloud-gateway/issues/3424. We could definitely improve things by relocating some of the code. It might be a good idea to get rid of the Jackson dependency if possible at that time since it is basically unsupported (hence the proto3 problems).
There is a problematic bug like https://github.com/spring-cloud/spring-cloud-gateway/issues/3783. In its pure state, I think SCG does not support gRPC.
That issue isn't relevant to the JsonToGrpcFilterFactory as far as I can tell (but it should be fixed too I agree). It's also kind of irrelevant to whether or not some of the code from Gateway could move to Spring gRPC (which is what this issue is tracking).