Architecture Intermediate

Hexagonal Architecture — Ports and Adapters¶

HexagonalPorts & AdaptersClean Code 3 min read

Separating business logic from infrastructure. Ports, adapters, and testable code.

Principle¶

Business logic does not depend on the database, framework, or UI. Ports = interfaces. Adapters = concrete implementations.

Structure¶

src/
├── domain/                    # Core — no dependencies!
│   ├── model/Order.ts
│   ├── ports/OrderRepository.ts  # Interface
│   └── services/OrderService.ts
├── application/
│   └── CreateOrderUseCase.ts
└── infrastructure/            # Adapters
    ├── persistence/PostgresOrderRepo.ts
    ├── payment/StripeGateway.ts
    └── web/OrderController.ts

Testability¶

Domain logic is tested with mock adapters — no database, no HTTP.

const mockRepo = { save: jest.fn() };
const service = new OrderService(mockRepo, mockPayment);
test('creates order', async () => {
    const order = await service.createOrder('cust-1', items);
    expect(order.status).toBe('CREATED');
    expect(mockRepo.save).toHaveBeenCalled();
});

Summary¶

Hexagonal architecture is an investment in maintainability. It pays off for projects with a longer lifespan.

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