Except it is not really embedded in Java, only in comments.
I sincerely hope this dies a quick death.
Java with its jars and infrastructure already makes it plenty convenient to work with resources without them having to be in your face when you are editing the file. Good IDE lets you move between the resource file and the code with a single click.
Yeah, I'm not sure I get it either. More power to the author for solving a problem they may have, but I have yet, in my 20+ years experience with Java, had a need to do this kind of code embedding in the source code (whether in comments or not). Sure, it's nice to be able to run other languages at run-time (e.g. GraalVM, etc), but is there really a need to have this kind of language interoperability at compile time?
Well, if you want to leverage Java's static type system (and why not?), the answer is, yes. I imagine you'd want type and member references to the other language to resolve statically using the compiler, right? Similarly, why not have the same functionality in your IDE? Plus code completion, usage searching, refactoring?
Now, as I mentioned in an earlier comment, the embedding part of this addresses just a small segment of use-cases e.g., scoped query editing. The vast majority of other cases work directly against resource files, type-safely. Read more about that here: