305 Frameworks Spring Boot Modulith Agent Skill

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

• 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.

• Model application modules

Identify business-capability modules, public APIs, internal packages, named interfaces, and intentional allowed dependencies.

• Apply framework-aligned changes

Add or refine Spring Modulith dependencies, package annotations, architecture verification tests, domain events, and module tests following the reference patterns.

• 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.