hexagonal-architecture

Hexagonal architecture is a structural pattern that isolates core domain logic from external infrastructure concerns like databases and UIs using ports and adapters. This separation ensures application logic remains decoupled, maintainable, and independently testable.

To structure an application with ports and adapters, define distinct Domain, Application, and Adapter layers. Establish clear naming conventions for components and data transfer objects to enforce boundaries and ensure system maintainability.

Both promote domain-infrastructure separation, but hexagonal architecture specifically emphasizes ports and adapters to route interactions, whereas clean architecture focuses broadly on dependency inversion across concentric layers to protect use cases.

Common hexagonal architecture anti-patterns include leaking infrastructure dependencies into the domain layer and misclassifying adapter responsibilities. Identifying these mistakes early prevents tight coupling and preserves the core application structure's integrity.

Refactor to a domain-driven design structure when testability and maintainability degrade due to mixed domain and infrastructure logic. Applying hexagonal architecture decouples the system, enabling isolated unit testing and clearer component boundaries.

Test separated domain and adapter layers by mocking external ports to isolate core business logic validation. Infrastructure adapters require integration tests, ensuring the application structure remains decoupled and thoroughly covered across boundaries.