Neat! I experimented with something similar and found the state of java AST transformers to be in a kind of painful state. I'll have to look though the code base to see what y'all used.
We used Google's Error Prone framework. Pros: you get full compiler symbol/type information, in addition to the AST. Cons: you need to build the code to process it (Error Prone runs as a javac plugin), and if you want to do things efficiently then you are restricted to basically a single AST traversal. It's very use-case dependent whether you are better off just using e.g. javaparser.