Software Architecture: Unveiling the Layered Architecture Pattern
In the realm of software development, understanding architectural patterns is essential. One such fundamental pattern is the Layered Architecture Pattern. This article aims to provide an in-depth analysis of the layered architecture pattern, including its description, key concepts, examples, and considerations.
Understanding Architectural Patterns
Architectural patterns in software design are pre-defined solutions to common design problems. They provide a structured approach to organizing components, defining their interactions, and establishing the fundamental layout of a system. These patterns guide decisions related to the system’s scalability, performance, and maintainability.
Our primary focus in this article is the Layered Architecture Pattern, frequently referred to as the n-tier architecture pattern. This pattern is the most used architecture design pattern, making it a common choice for most developers and architects.
Description of Layered Architecture Pattern
Components within the layered architecture pattern are organized into horizontal layers, each of which plays a specific role within the application. Even though the layered architecture pattern does not specify the number and types of layers that must exist within the pattern, most layered architectures comprise four standard layers: presentation, business, persistence, and database.
Key Concepts: Closed Layers and Request Access
Each of the layers in the architecture is marked as being closed. This concept is crucial in the layered architecture pattern. A closed layer means that as a request moves from layer to layer, it must go through the layer right below it to get to the next layer below that one.
For instance, a request originating from the presentation layer must first go through the business layer and then to the persistence layer before finally hitting the database layer. This concept is known as layers of isolation, which means that changes made in one layer of the architecture generally do not impact or affect components in other layers.
The Power of Layered Architecture: Separation of Concerns
One of the powerful features of the layered architecture pattern is the separation of concerns among components. Components within a specific layer deal only with logic that pertains to that layer. For example, components in the presentation layer deal only with presentation logic, whereas components residing in the business layer deal only with business logic. This type of component classification makes it easy to build effective roles and responsibility models into your architecture.
Layered Architecture Pattern in Action: An Example
To illustrate how the layered architecture pattern works, consider a request from a business user to retrieve customer information for a particular individual.
In this example, the customer information consists of both customer data and order data (orders placed by the customer). The customer screen is responsible for accepting the request and displaying the customer information. It does not know where the data is, how it is retrieved, or how many database tables must be queried to get the data.
Considerations When Using Layered Architecture Pattern
The layered architecture pattern is a robust general-purpose pattern, making it a good starting point for most applications. However, there are a few things to consider from an architecture standpoint when choosing this pattern.
One thing to watch out for is what is known as the architecture sinkhole anti-pattern. This anti-pattern describes the situation where requests flow through multiple layers of the architecture as simple pass-through processing with little or no logic performed within each layer.
Another consideration with the layered architecture pattern is that it tends to lend itself toward monolithic applications, even if you split the presentation layer and business layers into separate deployable units. While this may not be a concern for some applications, it does pose some potential issues in terms of deployment, general robustness and reliability, performance, and scalability.
Pattern Analysis of Layered Architecture
The layered architecture has its strengths and weaknesses. Here’s an analysis of common architectural characteristics for the layered architecture pattern:
· Overall agility: Low. It’s still cumbersome and time-consuming to make changes in this architecture pattern because of the monolithic nature of most implementations and the tight coupling of components.
· Ease of deployment: Low. One small change to a component can require a redeployment of the entire application, resulting in deployments that need to be planned, scheduled, and executed during off-hours or on weekends.
· Testability: High. Because components belong to specific layers in the architecture, other layers can be mocked or stubbed, making this pattern relatively easy to test.
· Performance: Low. The pattern does not lend itself to high-performance applications due to the inefficiencies of having to go through multiple layers of the architecture to fulfill a business request.
· Scalability: Low. Applications build using this architecture pattern are generally difficult to scale.
· Ease of development: High. This pattern becomes a natural choice for most business-application development.
Layered Architecture Pattern: A Deep-Dive
In the world of software development, the layered architecture pattern is a fundamental pattern that architects and developers commonly use. By understanding its key concepts, examples, and considerations, you can make informed decisions about the architecture that best suits your software requirements. As you continue learning about architectural patterns, remember that each pattern has its strengths and weaknesses, and the best pattern for your needs may be a combination of several patterns.
With the right architecture pattern, you can build software that is scalable, maintainable, and high-performing. So, take your time to understand each pattern and choose the one that best fits your project’s needs.
