Layered software architecture is a design pattern where an application is structured into distinct layers, each performing a specific set of related tasks, which promotes modularity and maintainability.
This architectural style organizes the system into horizontal layers, where each layer provides services to the layer above it and requests services from the layer below it. This creates a hierarchy, isolating layers from each other and allowing for changes within one layer without impacting others, provided the interface between layers remains consistent.
Key Characteristics of Layered Architecture:
- Abstraction: Each layer abstracts away the complexity of the layers below, providing a simplified interface to the layer above.
- Loose Coupling: Layers are designed to be loosely coupled, meaning they have minimal dependencies on each other. This facilitates independent development, testing, and deployment.
- Reusability: Layers can be reused across different parts of the application or even in different applications.
- Maintainability: Changes within one layer are less likely to affect other layers, making the system easier to maintain and update.
- Testability: Layers can be tested independently, simplifying the testing process.
Common Layers in a Layered Architecture:
While the specific layers can vary depending on the application, some common layers include:
- Presentation Layer (UI): Handles user interaction and displays information to the user.
- Application Layer (Business Logic): Implements the core business logic and rules of the application. This layer orchestrates the interactions between other layers.
- Domain Layer: This layer represents the concepts of the business domain. It typically contains entities, value objects, and domain services.
- Persistence Layer (Data Access): Provides access to the underlying data storage, such as a database.
- Infrastructure Layer: Provides supporting services, such as logging, security, and communication.
Benefits of Layered Architecture:
- Improved Maintainability: Changes are isolated within layers, reducing the risk of unintended consequences.
- Enhanced Testability: Layers can be tested independently.
- Increased Reusability: Layers can be reused across different parts of the application.
- Simplified Development: Development teams can work on different layers concurrently.
- Better Organization: The layered structure provides a clear and organized way to structure the application.
Considerations When Using Layered Architecture:
- Performance: Excessive layering can introduce overhead, potentially impacting performance. Consider the impact of each layer on overall system performance.
- Complexity: While it promotes organization, implementing a layered architecture can add complexity to the initial design.
- Tight Coupling: Care must be taken to avoid tight coupling between layers.
Example: E-commerce Application
In an e-commerce application, a layered architecture might look like this:
- Presentation Layer: User interface for browsing products, adding to cart, and placing orders.
- Application Layer: Processes orders, manages user accounts, and handles payment transactions.
- Domain Layer: Represents core e-commerce concepts such as Products, Orders, Customers, and Payments.
- Persistence Layer: Interacts with the database to store and retrieve product, order, and customer information.
In conclusion, layered software architecture is a powerful and widely used design pattern that promotes modularity, maintainability, and testability by dividing an application into distinct, interacting layers.
