| name | ca-kotlin |
| description | Clean Architecture rules and patterns for Kotlin + Spring Boot + Arrow-kt projects. Use when implementing or reviewing any CA layer: domain modeling, use case design, repository patterns, infrastructure implementation, or controller/DataFetcher wiring. Triggers on: domain entity design, value object creation, repository interface definition, use case implementation, jOOQ repository, REST controller, DGS DataFetcher, DI wiring.
|
Clean Architecture — Kotlin
Layer Dependency Direction
framework → presentation → application → domain ← infrastructure
CQRS Pattern
The application layer is split into command/ (writes) and query/ (reads):
- Command side:
application/command/ → uses domain repository (in domain/) → returns domain entities
- Query side:
application/query/ → uses query repository (in application/query/repository/) → returns flat DTOs
Key Patterns
| Concept | Pattern |
|---|
| Entity | data class Entity(val id: EntityId, ...) — val only, .copy() for updates |
| Value Object | @JvmInline value class VO private constructor(val value: T) with of() returning Either |
| Domain Error | sealed interface XxxError : DomainError |
| Domain Repo Interface | In domain/, write methods only (save, delete), returns Either<XxxError, T> |
| Command Use Case | interface XxxSaveUseCase in application/command/ — uses domain repository |
| Query Repo Interface | In application/query/repository/, read methods, returns Either<QueryError, QueryDto> |
| Query Use Case | interface XxxListQueryUseCase in application/query/ — uses query repository |
| Query DTO | data class XxxQueryDto(val id: Long, ...) — flat primitives, no domain types |
| Infra Domain Repo | @Repository class XxxRepositoryImpl(dsl: DSLContext) in infrastructure/command/repository/ |
| Infra Query Repo | @Repository class XxxQueryRepositoryImpl(dsl: DSLContext) in infrastructure/query/repository/ |
| REST Controller | @RestController injecting both command and query use cases |
| GraphQL DataFetcher | @DgsComponent injecting both command and query use cases |
| DI Wiring | @Bean for both command use cases (domain repo) and query use cases (query repo) |
Forbidden Imports by Layer
| Layer | Forbidden |
|---|
domain | org.springframework.*, jakarta.*, *.application.*, *.infrastructure.*, jOOQ |
application | Same as domain + no infra/presentation imports |
presentation | *.infrastructure.* only (may import *.domain.* for DTO mapping) |
Strict Rules
- NO
throw in domain/application/infrastructure — use Either
- NO
@Component/@Service on use case classes — wire manually via @Bean
- NO new library deps in
domain or application build.gradle.kts
This project uses jOOQ + R2DBC (NOT JPA). See references/layer-rules.md for detailed layer implementation examples. For Arrow-kt API patterns (either{}, .bind(), mapLeft, Either.catch, .fold()): see the arrow-kt skill.
