clean-architecture

# Clean Architecture, Hexagonal Architecture & DDD for Spring Boot ## Overview This skill provides comprehensive guidance for implementing Clean Architecture, Hexagonal Architecture (Ports & Adapters), and Domain-Driven Design tactical patterns in Java 21+ Spring Boot 3.5+ applications. It ensures clear separation of concerns, framework-independent domain logic, and highly testable codebases through proper layering and dependency management. ## When to Use - Architecting new Spring Boot applications with clear separation of concerns - Refactoring tightly coupled code into testable, layered architectures - Implementing domain logic independent of frameworks and infrastructure - Designing ports and adapters for swappable implementations - Applying Domain-Driven Design tactical patterns (entities, value objects, aggregates) - Creating testable business logic without Spring context dependencies ## Instructions ### 1. Understand the Core Concepts #### Clean Architecture Layers (Dependency Rule) Dependencies flow inward. Inner layers know nothing about outer layers. | Layer | Responsibility | Spring Boot Equivalent | |-------|---------------|----------------------| | **Domain** | Entities, value objects, domain events, repository interfaces | `domain/` - no Spring annotations | | **Application** | Use cases, application services, DTOs, ports | `application/` - `@`Service, `@`Transactional | | **Infrastructure** | Frameworks, database, external APIs | `infrastructure/` - `@...