The big difference between Java and Javascript when it comes to GraphQL is the amount of noise, tutorials and examples on the Javascript side far outweigh other options right now.
Javascript may be the "happy" path for now but I do hope that we see continued investment in Java/Scala/Ruby/Python/.NET etc as those implementations have the opportunity to be better architected and more performant that the reference JS implementation. The reference implementation uses a very simplistic execution model which for now has been copied almost verbatim into other languages but there is great potential for a proper query planner and optimisation layer at the GraphQL layer.
Disclaimer: I work at MDG on Apollo Engine (the backend of which is Kotlin utilising graphql-java).
I do agree on the noise and lack of tutorials. I'm getting ready to present on a GraphQL option. We don't want to use javascript. The tutorials for java are a bit cumbersome.
Btw I'm really liking apollo.
These last months, I've been working non-stop in a blazing-fast GraphQL engine that beats the rest by an order of magnitude - https://graphql-quiver.com/
The concept is great, and if you write custom SQL queries for each resolver (if necessary), properly caching things that can be cached, and use the first class citizen programming language (JavaScript), then it seems GraphQL works wonderfully.
Trying to fit it into an existing ORM paradigm with respect to complex sub-collections, lazy loading, and efficient database querying, it just didn’t work out for us.