[brucehart]

I would start looking for a new job immediately, but stay in your current job until you have something lined up. It's much easier to find a new job when you are already employed. Relax and just focus on developing your skills and learning as much as you can while you are there. What's the worst that could happen, you get fired or laid off? You are considering leaving the job off of your resume anyway. You might as well collect a paycheck while you are looking.

Learn everything you can about Java/Spring even if you never intend to write another line of Java in your career. It's always helpful to be familiar with other languages. Be polite to your employer and (when you have a new job lined up) just say you are moving on to an opportunity that is better aligned with your goals.

I once worked on a project that required refactoring classic ASP code written by a company in India. The code was a rat's nest. The site had hundreds of pages and most of them had three or four copies of the code commented out (this was their "version control system"). At the time I hated it, but looking back I learned a lot about what not to do and how to be a better programmer. I used the opportunity to create automated tools to clean up the code and experiment with new technologies.