305-frameworks-spring-boot-modulith

# Spring Boot - Spring Modulith Apply Spring Modulith guidelines for Spring Boot modular monoliths. **What is covered in this Skill?** - Spring Modulith BOM and starter dependency selection - Business-capability package structure for application modules - ApplicationModules verification and architecture tests - Named interfaces and explicit allowed dependencies - Domain events for loose coupling between modules - @ApplicationModuleTest and Scenario-based module integration tests - Generated module documentation, actuator exposure, and observability - Event publication registry choices for reliable domain events **Scope:** Apply recommendations based on the reference rules, official Spring Modulith documentation, and good/bad examples. ## Constraints Before applying Spring Modulith changes, ensure the project compiles. After improvements, run full verification including module structure tests. - **MANDATORY**: Run `./mvnw compile` or `mvn compile` before applying any change - **PRECONDITION**: The project must be a Spring Boot application; for non-Boot Java modularity use architecture or design skills instead - **BASELINE**: Align dependency choices with Spring Boot 4.0.x and the Spring Modulith compatibility matrix - **SAFETY**: If compilation fails, stop immediately - **VERIFY**: Run `./mvnw clean verify` or `mvn clean verify` after applying improvements - **BEFORE APPLYING**: Read the reference for detailed rules, good/bad patterns, and official documentation links ## When to use this skill - Add Spring Modulith to a Spring Boot application - Review Spring Modulith module boundaries - Improve modular monolith architecture in Spring Boot - Add @ApplicationModuleTest tests - Generate Spring Modulith documentation - Refactor Spring Boot modules with Spring Modulith ## Workflow 1. **Read reference and inspect project structure** Read `references/305-frameworks-spring-boot-modulith.md` and inspect the Spring Boot version, Maven dependencies, main application package, and current package/module boundaries. 2. **Model application modules** Identify business-capability modules, public APIs, internal packages, named interfaces, and intentional allowed dependencies. 3. **Apply framework-aligned changes** Add or refine Spring Modulith dependencies, package annotations, architecture verification tests, domain events, and module tests following the reference patterns. 4. **Run verification and report results** Execute appropriate build/tests, especially `ApplicationModules.verify()` and `@ApplicationModuleTest` coverage, then summarize changes, risks, and follow-up module design work. ## Reference For detailed guidance, examples, and constraints, see [references/305-frameworks-spring-boot-modulith.md](references/305-frameworks-spring-boot-modulith.md).