genjava_message_artifacts empty jar for custom services

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I am trying to incorporate custom services into my rosjava project. I have copied the directory containing all the srv files (there are no custom messages, just services), but when I run genjava_message_artifacts it generates a jar for me, but the jar is completely empty.

I have tried adding the directory into the rosjava_minimal/src directory as well, but - again - I end up with no class files being generated.

If anybody could please help, it would be greatly appreciated. It just will not cooperate and generate the jar that I need to continue my work.

Thanks.