Refactoring and Retrofitting Design Patterns in Java Software Product Lines

A centerpiece of modern software development is refactoring. Software Product Lines (SPLs), a major software development paradigm, lack tools to refactor Java SPL codebases. X15 introduces our new set of design guidelines, techniques, and language constructs to (1) express feature-based Java SPLs using only Java custom annotations, (2) view programs of the SPL, (3) edit views, automatically propagating edits back to the SPL codebase, (4) verify refactoring preconditions are satisfied by the target program as well as all SPL programs, (5) refactor programs, automatically applying a corresponding refactoring to the SPL codebase, and (6) retrofit design patterns into the SPL codebase by executing refactoring scripts. X15 implements a core theorem on refactoring feature-based Java SPLs. Case studies apply 2,316 refactorings to retrofit 64 pattern instances in 8 public Java SPLs and show that X15 is as efficient, expressive, and scalable as a state-of-the-art feature-unaware refactoring engine.