Fine-grained patches for Java software upgrades

We present a novel methodology for deriving fine-grained patches of Java software. We consider an abstract-syntax tree (AST) representation of Java classes compiled to the Java Virtual Machine (JVM) format, and a difference analysis over the AST representation to de-rive patches. The AST representation defines an appro-priate abstraction level for analyzing differences, yield-ing compact patches that correlate modularly to actual source code changes. The approach contrasts to other common, coarse-grained approaches, like plain binary differences, which may easily lead to disproportionately large patches. We present the main traits of the method-ology, a prototype tool called aspa that implements it, and a case-study analysis on the use of aspa to derive patches for the Java 2 SE API. The case-study results il-lustrate that aspa patches have a significantly smaller size than patches derived by binary differencing tools.