Annotation refactoring

Since annotations were added to the Java language, many frameworks have moved to using annotated Plain Old Java Objects (POJOs) in their newest releases. Legacy applications are thus forced to undergo extensive restructuring in order to migrate from old framework versions to new versions based on annotations ( Version Lock-in ). Additionally, because annotations are embedded in the application code, changing between framework vendors may also entail largescale manual changes ( Vendor Lock-in ). This paper presents a novel refactoring approach that effectively solves these two problems. Our approach infers a concise set of semantics-preserving transformation rules from two versions of a single class. Unlike prior approaches that detect only simple structural refactorings, our algorithm can infer general composite refactorings and is more than 97% accurate on average. We demonstrate the effectiveness of our approach by automatically upgrading more than 80K lines of the unit testing code of four open-source Java applications to use the latest version of the popular JUnit testing framework.