OpenRewrite vs Spoon

OpenRewrite is an open-source ecosystem for automated code refactoring, aimed at updating code and reducing technical debt. It represents code as Lossless Semantic Trees, applies transformations, and prints the result back into source code for review. Its recipes cover framework migrations, security fixes, and style consistency, and can be written in YAML, Refaster templates, or Java. Maven and Gradle plugins run recipes locally as part of builds, one repository at a time. The Maven plugin offers a dry run that reports potential changes and writes diff files; recipes run only when explicitly activated by name. Documented support includes Java, Kotlin, and Groovy, plus formats such as HCL, JSON, Properties, Protobuf, TOML, XML, and YAML. Framework coverage includes Spring, Quarkus, and Micronaut. The recipe index lists 4,183 recipes across modules. Core and language libraries use Apache License 2.0, but some recipes have other licensing terms. Core is free; some artifacts require authenticated repository access, and some recipes require a Moderne subscription.

Spoon is a free, open-source library for analyzing, rewriting, transforming, and transpiling Java source code. It parses source files into an abstract syntax tree (AST), then exposes APIs for inspecting and changing that model. Processors can perform source-level static analysis on selected AST element types, while architectural rules can be expressed as AST checks and run as JUnit tests in continuous integration. Transformation facilities cover instrumentation and refactoring, including helpers for local and generic variables and removing deprecated methods. Spoon can also provide shared analysis of binary and source code through CtClass objects as an alternative to Java reflection. The project supports Java source up to Java 25, but runtime requirements vary: Spoon 11.x needs JDK 17 or later, 10.x needs JDK 11 or later, and 9.x needs Java 8. It is available through Java, the command line, Maven, and Gradle, with a dependency JAR on Maven Central. Command-line use requires manual classpath handling and source dependencies specified with --source-classpath. Spoon is an official Inria project and an OW2 consortium member.