Layer structure in software architecture involves organizing a system into distinct layers, each with a specific responsibility.
Understanding Layered Architecture
Layered architecture is a common approach in software design. It's all about dividing a complex system into manageable, logical sections. The core concept is that each layer provides a service to the layer above it and relies on the layer below. This creates a hierarchical structure.
Key Characteristics
- Logical Grouping: Layers group components based on their function and how they interact with others. This makes the system easier to understand and maintain.
- Interlayer Communication: Interaction between layers happens through defined interfaces, usually between adjacent layers only. This reduces dependencies and promotes modularity.
- Abstraction: Each layer hides its internal implementation from other layers, exposing only necessary interfaces. This enables flexibility and independent development.
How Layers Interact
Communication in a layered architecture usually happens in a top-down manner. A request originating in a higher layer passes down through the layers until it is eventually handled by a low-level layer, then the response is propagated back up.
Common Layers (Example)
Here's a common example with four layers:
| Layer Name | Description | Example Components |
|---|---|---|
| Presentation | Handles user interface components like UI and web pages. | React, Angular, HTML, CSS |
| Application | Implements business logic and manages user requests. | Services, Use Cases, Application Logic |
| Domain | Represents core business concepts and rules. | Entities, Value Objects, Domain Services |
| Infrastructure | Provides access to lower-level resources like databases, APIs, and files. | Databases, File Systems, Cloud APIs |
Benefits of Layered Architecture
- Organization: Clearly separates concerns and simplifies system structure.
- Maintainability: Changes to one layer are less likely to affect other layers.
- Testability: Layers can be tested individually.
- Reusability: Components within a layer can be reused in other parts of the application.
- Flexibility: Layers can be replaced or modified as needed.
Practical Insights
- Layer Isolation: Enforce strict boundaries between layers to avoid circular dependencies.
- Layer Size: Keep layers focused and well-defined. Overly granular layers can add unnecessary complexity.
- Layer Communication: Use well-defined interfaces between layers. Don't bypass layers to avoid tight coupling.
Example: E-commerce Application
Imagine an e-commerce application. The presentation layer will handle the user interface, the application layer will manage the shopping cart and order process, the domain layer will encapsulate business logic like inventory management, and the infrastructure layer will interact with the database.
Summary
Layered software architectures, as the provided reference points out, consist of multiple layers of components that are placed into logical groupings based on the type of functionality they provide or based on their interactions with other components, such that interlayer communication occurs between adjacent layers. It is a powerful tool to build manageable, maintainable, and scalable software systems.
