I've never refused to work on stuff I don't like I just charge more for it, usually a percentage.

A multi-million dollar project that can be killed because someone doesn't want to write java interop code is something I want to support, most people mistake me for a programmer, I'm a business guy who knows how to code, what the bossman has in this situation is a win-win situation, his programmer gets to keep writing python, I get to write java interop code for a percentage of the project, and he gets a project finished.