In the world of software development, the term "Clean Architecture" is frequently discussed, yet its true essence often remains elusive. Let's demystify this concept and shed light on the fundamentals of clean architectures in a straightforward manner.
At its core, Clean Architecture is a software design approach that places a strong emphasis on separating concerns and achieving modular organization, with well-defined layers and responsibilities. The ultimate goal? Creating systems that are highly maintainable, scalable, and testable. Clean Architecture strives to keep source code clean, independent of frameworks and technologies, thus enabling seamless adaptability to changes and enhancements over time.
Within the realm of clean architectures, several distinctive approaches exist, each offering its own set of advantages and drawbacks. Among these approaches, we find notable names such as Layered Architecture, Hexagonal Architecture (also known as Ports and Adapters), Onion Architecture, Impure Domain Architecture, Schema Architecture, and, quite explicitly, Clean Architecture itself.
An Additional Key Insight: Avoiding Infrastructure Contracts in the Domain Layer
A prevalent and subtle mistake when implementing Clean Architecture is the direct introduction of contracts (Ports) for external concerns—such as repository interfaces or service clients from specific providers—directly into the Domain layer. While it's correct to depend on abstractions, the nature of these abstractions is critical. The Domain should contain only the pure business logic and rules that are fundamental to the problem being solved. When we define an interface like IUserRepository or IPaymentGateway within the Domain, we are implicitly modeling a technical concern (persistence, external communication) and dictating a data-access or integration pattern to the core business rules. This contaminates the domain with a narrative of implementation, binding it to a specific architectural pattern (like the Repository pattern) or a technological context (like "gateways"). Consequently, the Domain is no longer solely about the essential business concepts but becomes cluttered with solutions to infrastructure problems, violating the Dependency Rule and reducing its purity and longevity.
The Correct Abstraction: Domain-Centric Contracts
The proper approach is to ensure that all contracts owned by the Domain layer are expressed exclusively in terms of domain language and abstract, and eventually facades (compute libraries invertion), not technical mechanisms. Instead of a generic IRepository<T>, the Domain should define application-specific service interfaces, such as IUserRegistry or IOrderFulfillmentService, which declare the intent required by the business processes (e.g., ActiveCustomersByRegion, ProcessedPaymentForOrder). These interfaces articulate what the business needs, not how it should be achieved (e.g., via a SQL database, a REST API, or an event stream). The concrete implementations of these contracts—the Adapters—are then provided in the outer layers (Infrastructure/Data), which in turn may use generic technical patterns like Repositories or API clients. This inversion keeps the Domain completely agnostic of technical decisions, frameworks, and data sources, truly embodying the independence that Clean Architecture promises and ensuring that the core business rules remain the most stable and isolated part of the system.
Maybe in upcoming articles, we will delve deeper into each of these architectural paradigms, unraveling their intricacies and exploring their practical applications. Stay tuned for a journey through the world of clean architectures!
Top comments (0)