I was almost bitten by a project like this, despite ample protests the whole way long that "configuration" was just becoming a "crappy programming language". All too often I still have to deal with someone who thinks because logic hinges on a value in a JSON file, they've magically abstracted away the concern of what it is that the code should be doing.
Man, I'm not from the Java world, but these days I had to deal with it for a project and had to mess with ant builds, which I have never dealt with before. I was totally baffled. I just do not understand why would anyone subject themselfs to such levels of pain.