I am planning to autogenerate a set of Java libs from OpenAPI 3.1 definitions in an upcoming project, and so far have assumed it would Just Work. Am I going to have a bad time?
It's hard to say. It may be that the Java ecosystem for it is in good shape. The generator tools are almost all Java, so you might have the best-case scenario.
The OpenAPI Generator uses Mustache templates and a plug-in-style design to handle all the different languages and outputs targeting different packages. I was never able to find a succinct document explaining exactly how the processing steps worked or even a catalog of data elements that the generator extracted from your OpenAPI spec document (YAML or JSON). So while there's a lot of talk about creating a custom template, or, if that's not enough, a custom generator... the documentation to do so is very incomplete. The only example I found all discussed making a generator for documentation and not code. Again, not to sound unappreciative, but... that's lame.
