Comparison Table: Hexagonal, Clean, Onion, and Traditional Layered Architectures
October 10, 2023 ยท View on GitHub
| Aspect | Traditional Layered Architecture | Clean Architecture | Onion Architecture | Hexagonal Architecture |
|---|---|---|---|---|
| Definition | Divides the application into layers based on functionality, with each layer having dependencies on the layer below it | Emphasizes separation of concerns and the use of SOLID principles for building scalable and maintainable software | Similar to Hexagonal Architecture, it aims to decouple the application core from the infrastructure layers. However, it adds the concept of concentric layers | Also known as Ports and Adapters Architecture, it focuses on separating the application core from the surrounding infrastructure layers |
| Dependency Flow | Dependencies flow from higher-level layers to lower-level layers, with each layer depending on the layer directly below it | The dependency flow is unidirectional, with higher-level layers depending on lower-level layers. Dependencies are not allowed to flow in the opposite direction | Similar to Hexagonal Architecture, the dependency flow is inward, with the core defining interfaces and the adapters implementing them | The flow of dependencies is inward, with the application core defining interfaces (ports) that are implemented by the adapters. The adapters depend on the interfaces defined by the core |
| Dependency Inversion Principle (DIP) Support | May not explicitly enforce the DIP, leading to potentially tightly coupled dependencies between layers | Emphasizes the DIP by using interfaces and dependency injection to invert dependencies, enabling higher-level layers to depend on abstractions defined by lower-level layers | Supports the DIP by using interfaces to define dependencies between layers, allowing for the inversion of dependencies and loose coupling | Strongly aligns with the DIP by relying on interfaces (ports) that are implemented by adapters, allowing the core to depend on abstractions |
| Deployment and Infrastructure | May have tight coupling with the infrastructure, making it more difficult to adapt or switch deployment environments without impacting the entire system | Is agnostic to the deployment and infrastructure details, allowing for easy adaptation to different environments | Separates infrastructure concerns into outer layers, making it easier to adapt or switch to different deployment environments without affecting the core | Abstracts away the infrastructure, making it easier to switch or adapt to different deployment environments without affecting the core |
| Flexibility and Adaptability | Can be less flexible and adaptable due to tight coupling, making it harder to change or replace components without impacting other parts of the system | Promotes flexibility and adaptability by enforcing separation of concerns, allowing for independent modification of layers without affecting others | Provides flexibility and adaptability by separating concerns into layers, making it easier to change or replace components without affecting other layers | Offers high flexibility and adaptability by isolating the core from external dependencies, making it easier to switch or upgrade components |
| Layering Philosophy | Layers are organized vertically based on functionality, with each layer providing services to the layer above it | Layers are organized based on business logic and responsibilities. Each layer has a clear purpose and can depend only on the layer below it | Concentric layers approach: The innermost layer represents the core business logic and the outer layers handle infrastructure and frameworks | Ports (interfaces) and Adapters (implementations) are the core elements. The application core is isolated from the external dependencies |
| Scalability and Maintainability | Can be scalable and maintainable, but tight coupling between layers can make it more challenging to modify or add new features without affecting other parts of the system | Promotes scalability and maintainability by enforcing separation of concerns and dependency inversion, making it easier to modify and add new features without impacting other parts of the system | Aims to improve scalability and maintainability through its layered approach, allowing for easier modification and replacement of components without affecting other layers | Enables scalability and maintainability by decoupling the application core from the infrastructure, allowing for easier modification and replacement of external dependencies |
| Testing and Isolation | Can make testing more challenging due to tight coupling between layers, requiring more complex integration testing | Advocates for testability by employing dependency inversion and interfaces, enabling mocking and unit testing of individual layers | Emphasizes testability through the use of interfaces and dependency injection, allowing for isolated testing of the core business logic | Promotes easier testing and isolation of the application core by using ports and adapters, allowing the core to be tested independently of the infrastructure |
| Use cases | - project requires a simple and straightforward architecture - project involves a small number of external integrations - project requires a high degree of scalability | - project requires a high degree of maintainability and understandability - project involves a large number of business rules and use cases - project requires a high degree of testability | - project requires a high degree of flexibility and maintainability - project involves a large number of complex business rules and domain logic - project requires a high degree of testability | - project requires a high degree of testability and maintainability - project involves a large number of external integrations, such as databases, file systems, or web services - project requires a high degree of flexibility, such as the ability to switch from one technology to another |