Outbound port interfaces usually live in the application layer (or in domain only when the abstraction is truly domain-level), while infrastructure adapters implement them.

Dependency direction is always inward:

• Adapters -> application/domain
• Application -> port interfaces (inbound/outbound contracts)
• Domain -> domain-only abstractions (no framework or infrastructure dependencies)
• Domain -> nothing external

How It Works

Step 1: Model a use case boundary

Define a single use case with a clear input and output DTO. Keep transport details (Express req, GraphQL context, job payload wrappers) outside this boundary.

Step 2: Define outbound ports first

Identify every side effect as a port:

• persistence (UserRepositoryPort)
• external calls (BillingGatewayPort)
• cross-cutting (LoggerPort, ClockPort)

Ports should model capabilities, not technologies.

Step 3: Implement the use case with pure orchestration

Use case class/function receives ports via constructor/arguments. It validates application-level invariants, coordinates domain rules, and returns plain data structures.

Step 4: Build adapters at the edge

• Inbound adapter converts protocol input to use-case input.
• Outbound adapter maps app contracts to concrete APIs/ORM/query builders.
• Mapping stays in adapters, not inside use cases.

Step 5: Wire everything in a composition root

Instantiate adapters, then inject them into use cases. Keep this wiring centralized to avoid hidden service-locator behavior.

Step 6: Test per boundary

• Unit test use cases with fake ports.
• Integration test adapters with real infra dependencies.
• E2E test user-facing flows through inbound adapters.

Architecture Diagram

flowchart LR
  Client["Client (HTTP/CLI/Worker)"] --> InboundAdapter["Inbound Adapter"]
  InboundAdapter -->|"calls"| UseCase["UseCase (Application Layer)"]
  UseCase -->|"uses"| OutboundPort["OutboundPort (Interface)"]
  OutboundAdapter["Outbound Adapter"] -->|"implements"| OutboundPort
  OutboundAdapter --> ExternalSystem["DB/API/Queue"]
  UseCase --> DomainModel["DomainModel"]

Suggested Module Layout

Use feature-first organization with explicit boundaries:

src/
  features/
    orders/
      domain/
        Order.ts
        OrderPolicy.ts
      application/
        ports/
          inbound/
            CreateOrder.ts
          outbound/
            OrderRepositoryPort.ts
            PaymentGatewayPort.ts
        use-cases/

…

santa-method

通过双评审智能体对结果进行对抗式校验，提升输出发布前的可靠性