Introduction

An Onion Architecture tries to create applications as modular as possible. This should make the maintenance of the application easier. It also aims to provide a basis for developing flexible, testable, and extensible code.
The large goal of the architecture is to make components easily exchangeable, without affecting other parts of the application, by avoiding fixed dependencies and instead only using Interfaces as contracts between components.

Concepts

Dependencies

In an Onion Architecture, the dependencies flow from the outer layers to the inner layers. This allows the inner modules to work without knowing about the outer layers. This avoids fixed dependencies, making it possible to easily swap components. This without the need to touch other parts of the application.

Layers

Domain: In the domain layer, the different business domains required by the application are depicted. This is where the actual business cases with their logic and entities are implemented.

Application: The application layer allows the different use cases to work. For this the application layer enables the flow of data between the different components and layers of the application.

Infrastructure: The infrastructure layer provides the interfaces to the outside world. It implements the communication of the application with other services and systems. For example like a database, a REST-API or many other services needed / used by the application.

Presentation: The presentation layer is part of the infrastructure. But instead of communication with other systems, it communicates with the user. This is done by providing a user interface like a website for example.

Model of an Onion Architecture
Model of the Onion Architektur

Edit this page

Last updated 27 Nov 2024, 15:01 +0100 . history