What’s up, guys! For those of you who have been following my articles, you’ve likely noticed this ongoing series where I explore different software architecture concepts. In today’s episode, we’re diving into Hexagonal Architecture — more specifically, the Ports and Adapters pattern, one of its core principles for building flexible, testable, and highly maintainable systems.
The idea behind Ports and Adapters or Hexagonal emerged as an evolution of the traditional Four-Layer Architecture model, introducing a more flexible and decoupled approach. But that’s a deeper discussion we can save for another time.
In this architecture, the application is represented as a hexagon. Inside the hexagon, we have the domain entities and their use cases, which do not depend on any external components. All dependencies are directed inward, toward the center.
The core of the hexagon — the domain — remains completely independent and free from external dependencies. This ensures that the business logic is clearly separated from the technical layers, and reusable domain logics.
Outside the hexagon, we find different adapters that interact with the application. Each adapter is responsible for communicating with a specific external actor or system. For instance, there may be a web adapter that handles interactions with a web browser, integration adapters that communicate with external services, and a persistence adapter responsible for interacting with a database.
Adapters on the left side are considered driving adapters, as they initiate interactions with the application by invoking the core. Examples include REST controllers, message consumers, or UI components. On the other hand, adapters on the right side are driven adapters, as they are invoked by the application core to perform external operations, such as database access, external API calls, or messaging.
Adapters effectively represent the external interfaces of the application or clients to other systems. They rely on ports to communicate with the core. A REST controller, for example, acts as an adapter that uses an input port to trigger a use case within the application.
The application core defines these ports as contracts, ensuring that communication remains consistent and decoupled from implementation details. Ports act as technology-agnostic entry and exit points, allowing adapters to be connected or replaced without impacting the domain logic. This design reinforces a clean separation between business rules and infrastructure concerns, improving maintainability, testability, and flexibility.
I hope this article was helpful in some way—happy coding! 🚀
Feel free to share your thoughts or suggestions in the comments below!
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