cleanarkkitehtuurit

Clean architecture, or cleanarkkitehtuurit in Finnish, is a software design philosophy that emphasizes the separation of concerns and the independence of the software's core logic from external frameworks, UI, and databases. The primary goal is to create systems that are easy to understand, test, and maintain, while also being adaptable to future changes.

At its core, clean architecture organizes software into concentric layers. The innermost layer represents the entities, which are the core business objects and rules that are least likely to change. Moving outwards, the next layer contains use cases, which define the specific operations the system can perform using the entities. These use cases are independent of any specific interface or database.

Further out are the interface adapters, responsible for converting data between the use cases and external agencies like UIs, databases, or web services. The outermost layer consists of frameworks and drivers, which include specific technologies like web frameworks, databases, and external libraries.

A key principle is the dependency rule, which states that dependencies can only point inwards. The inner layers should not know anything about the outer layers. This ensures that the core business logic remains stable and unaffected by changes in external technologies. This layered approach promotes testability, as business rules can be tested in isolation without the need for a UI or database. It also facilitates easier migration of external components, as the core system is not tied to any specific implementation.