# OpenRewrite — Automated Mass Refactoring for Source Code

> Automated source code refactoring engine for Java and other JVM languages, applying safe, tested transformation recipes at scale.

## Install

Save as a script file and run:

# OpenRewrite — Automated Mass Refactoring for Source Code

## Quick Use
```bash
# Apply a recipe via the Maven plugin
mvn -U org.openrewrite.maven:rewrite-maven-plugin:run 
  -Drewrite.recipeArtifactCoordinates=org.openrewrite.recipe:rewrite-migrate-java:RELEASE 
  -Drewrite.activeRecipes=org.openrewrite.java.migrate.UpgradeToJava17
# Or with Gradle
plugins { id("org.openrewrite.rewrite") version("latest.release") }
rewrite { activeRecipe("org.openrewrite.java.migrate.UpgradeToJava17") }
# Then run: gradle rewriteRun
```

## Introduction
OpenRewrite is an automated refactoring engine that applies deterministic transformations to source code at scale. It parses code into a lossless semantic tree (LST) preserving formatting and whitespace, then applies composable recipes to migrate frameworks, fix vulnerabilities, or upgrade language versions.

## What OpenRewrite Does
- Migrates Java applications between major versions (Java 8 to 17, 17 to 21)
- Upgrades framework dependencies such as Spring Boot, JUnit, and Jakarta EE
- Applies security patches by replacing vulnerable API calls and dependencies
- Enforces coding standards and style rules across repositories
- Transforms build files (Maven POM, Gradle) alongside source code

## Architecture Overview
OpenRewrite operates on a Lossless Semantic Tree (LST) that retains every character of the original file. Parsers convert source into LSTs, then recipes — composed of visitors — traverse and modify the tree. The printer serializes the LST back to text with minimal diff. Recipes are distributed as Maven artifacts and can be composed into migration plans.

## Self-Hosting & Configuration
- Runs as a Maven or Gradle build plugin with no separate server required
- Configure active recipes and styles in pom.xml or build.gradle
- Recipe modules are pulled from Maven Central as regular dependencies
- The rewrite.yml file allows custom recipe composition and parameter overrides
- Moderne CLI provides optional commercial multi-repo orchestration

## Key Features
- Lossless Semantic Tree preserves original formatting after transformations
- Pre-built recipes covering Java, Kotlin, Groovy, XML, YAML, and properties files
- Composable recipes — combine visitors into large migration plans
- Dry-run mode previews changes as diffs before applying
- Type-aware refactoring resolves method signatures, imports, and class hierarchies

## Comparison with Similar Tools
- **Error Prone** — Catches bugs at compile time; OpenRewrite applies fixes across entire repos
- **Refaster** — Template-based refactoring in a single build; OpenRewrite supports cross-repo distribution
- **Semgrep** — Pattern-based linting; OpenRewrite uses a full semantic tree for type-aware transforms
- **jscodeshift** — JavaScript AST transforms; OpenRewrite targets JVM languages with format preservation

## FAQ
**Q: Does OpenRewrite modify code in place?**
A: Yes, `rewriteRun` applies changes directly. Use `rewriteDryRun` to generate a diff report first.

**Q: Can I write custom recipes?**
A: Yes. Recipes are Java classes extending visitor patterns on the LST. You can also compose existing recipes in YAML.

**Q: Does it support languages beyond Java?**
A: It has parsers for Kotlin, Groovy, XML, YAML, JSON, and properties files.

**Q: Will it break my formatting?**
A: The LST preserves original formatting. Transformations only change targeted code.

## Sources
- https://github.com/openrewrite/rewrite
- https://docs.openrewrite.org

---
Source: https://tokrepo.com/en/workflows/asset-c9f88758
Author: Script Depot