The Layered pattern is a popular software architectural pattern that is used to organize an application into logical layers, each of which has a specific responsibility. Each layer communicates only with its immediate neighbor, which helps to reduce dependencies and make the application more modular and scalable.
The Layered pattern consists of three main layers: the Presentation layer, the Business layer, and the Data Access layer. Let’s take a closer look at each of these layers.
- Presentation Layer The Presentation layer is responsible for presenting data to the user and receiving input from the user. This layer is usually implemented as a graphical user interface (GUI) or a web interface. The Presentation layer does not contain any business logic or data access code; its sole responsibility is to provide a user-friendly interface for the user.
- Business Layer The Business layer contains the application’s business logic. It is responsible for implementing the business rules that govern how the application works. This layer receives input from the Presentation layer and communicates with the Data Access layer to retrieve and store data. The Business layer also performs any necessary transformations or calculations on the data before passing it back to the Presentation layer.
- Data Access Layer The Data Access layer is responsible for accessing the application’s data store. This layer communicates with the Business layer to retrieve and store data. The Data Access layer may use a variety of data storage technologies, such as relational databases, object-oriented databases, or file systems. This layer should be designed to be flexible, allowing for easy integration with different data storage technologies.
In the Layered pattern, each layer has a specific responsibility and communicates only with its immediate neighbor. This helps to reduce dependencies and make the application more modular and scalable. For example, changes to the Data Access layer should not affect the Business layer, and changes to the Business layer should not affect the Presentation layer.
Benefits of the Layered pattern:
- Separation of Concerns: The Layered pattern separates the concerns of an application into logical layers, each with a specific responsibility. This separation of concerns makes the code easier to understand, modify, and maintain. Each layer has a well-defined responsibility, which makes it easier to identify and isolate bugs or issues within the code.
- Modularity: The Layered pattern creates a modular design, where each layer is independent of the others. This makes it easier to modify and maintain the application over time. Changes made to one layer should not affect the other layers, making it easier to add new features or update existing ones.
- Scalability: The Layered pattern allows an application to scale horizontally by adding additional instances of the same layer, or vertically by adding additional layers. This scalability is essential for applications that need to handle a growing number of users or requests.
- Flexibility: The Layered pattern allows for flexibility in the design of each layer, making it easy to switch out different technologies or components as needed. For example, the Data Access layer could use a relational database or a NoSQL database, depending on the specific needs of the application.
- Testability: The Layered pattern makes it easier to write automated tests for the application. Each layer can be tested independently, which makes it easier to identify and fix bugs or issues within the code.
- Reusability: The Layered pattern promotes the reuse of code across the application. For example, the Data Access layer can be used by multiple Business layers, reducing the amount of duplicate code in the application.
The Layered pattern is a powerful tool for organizing an application’s code into logical layers. By separating the application’s concerns into these layers, it becomes easier to understand, modify, and maintain the code over time. The Layered pattern is widely used in modern software development, and it is an essential tool for building robust, scalable, and maintainable applications.