Understanding Software Architecture Patterns and Design Principles: Chapter 2

Welcome back, everyone! In this new chapter of our software architecture journey, we explore the fascinating realms of architectural patterns and design principles, two essential aspects unlock the grand concept of software architecture. So, without further ado, let’s dive right in.

What exactly are Architectural Patterns, and how many of them exist in the software world? While we won’t be able to explore the vast array of Architectural Patterns comprehensively, we’ll concentrate on the five most common ones you’re likely to encounter in your real-world projects, complete with real-world examples to illustrate their practicality.

Architectural patterns play an important role in shaping the way software systems are designed and organized. They provide a proven structure for building applications and offer a consistent methodology or pattern for addressing common challenges in software development. Let’s look into some of the most prominent architectural patterns and understand their significance.

1. MVC (Model-View-Controller):

• Description: MVC separates an application into three interconnected components: Model, View, and Controller. The Model represents the data and business logic, the View handles the user interface, and the Controller manages user input and updates the Model and View accordingly.
• Real-World Example: Web applications like Ruby on Rails use MVC. In this context, the Model represents the application’s data and database interactions, the View generates HTML templates, and the Controller handles HTTP requests.

2. MVVM (Model-View-ViewModel):

• Description: MVVM is particularly popular in the context of front-end development. It separates the application into Model, View, and ViewModel. The ViewModel contains the presentation logic and data formatting, bridging the Model and View.
• Real-World Example: Angular, a front-end framework, follows the MVVM pattern. The Model is represented by data structures, the View is HTML templates, and the ViewModel is managed by Angular components, which provide a bridge between the Model and View.

3. MVP (Model-View-Presenter):

• Description: MVP is similar to MVC but places a stronger emphasis on the separation of concerns. The Presenter acts as an intermediary between the Model and View, taking care of user interface logic.
• Real-World Example: GWT (Google Web Toolkit) uses the MVP pattern for web applications. The Presenter in GWT handles client-side logic and communicates with the server-side Model.

4. MVA (Model-View-Adapter):

• Description: MVA is an extension of the Model-View-Controller (MVC) pattern. It introduces an Adapter component that mediates between the Model and View, facilitating their interactions.
• Real-World Example: Java Swing, a GUI toolkit, uses the MVA pattern. The Adapter in Swing allows a single Model to interact with multiple Views, making it a flexible choice for GUI applications.

5. Layered (N-Tier) Architecture:

• Description: Layered architecture divides an application into multiple layers, each responsible for a specific aspect of the application. This typically includes presentation, business logic, and data access layers.
• Real-World Example: Enterprise applications often adopt this pattern. For instance, in a Java EE application, the presentation layer handles user interactions, the business logic layer contains the application’s core functionality, and the data access layer communicates with the database.

I understand that this might seem overwhelming, but let’s break it down. Architectural patterns revolve around dividing a system into distinct components, each with its unique role in the system. While these patterns typically involve three components, the Model and View components are consistent across Patterns 1 through 4. The third component varies in name based on its function within each pattern.

1. Model: In each of these patterns, the “Model” represents the application’s data, business logic, or underlying information. It can be thought of as the core component that manages data storage, retrieval, and manipulation.
2. View: The “View” is responsible for the user interface and presentation layer. It handles rendering and displaying data to the user and receiving user input.
3. The core components (Controller, ViewModel, Presenter, and Adapter) primarily act as intermediaries, facilitating the management and processing of data. Their essential role is to maintain a distinct separation of concerns, effectively mediating interactions between the “Model” (housing data and business logic) and the “View” (comprising the user interface).

Now that we’ve gained a solid grasp of architectural patterns, let’s dive a bit deeper and explore the realm of design principles.

Design Principles act as guiding rules for creating clean and efficient code, reducing complexity, and ensuring extensibility. Let’s explore some fundamental design principles that underpin architectural excellence.

SOLID Principles:

• Single Responsibility Principle (SRP): This principle emphasizes that a class should have only one reason to change. In other words, a class should have a single responsibility, making it easier to understand and maintain. For example, a FileHandler class should handle file operations and not be responsible for data validation.
• Open-Closed Principle (OCP): The Open-Closed Principle states that software entities (classes, modules, functions) should be open for extension but closed for modification. When you need to add new functionality, you should do so without altering existing code. An example is creating a plugin system that allows extending an application’s features without modifying its core code.
• Liskov Substitution Principle (LSP): This principle asserts that objects of a derived class should be able to replace objects of the base class without affecting the program’s correctness. It ensures that derived classes maintain the expected behavior of the base class. An example is the inheritance of different animal species from a common Animal base class.
• Interface Segregation Principle (ISP): ISP suggests that no client should be forced to depend on methods it does not use. It promotes the creation of specific, client-focused interfaces. For instance, an interface for a document editor might separate methods for text editing from methods for image manipulation.
• Dependency Inversion Principle (DIP): DIP advocates high-level modules depending on abstractions rather than concrete implementations. It encourages the use of interfaces or abstract classes to achieve loose coupling. A real-world application is the implementation of dependency injection in a project to facilitate testing and decouple components.

The SOLID principles are a set of five design principles, and the Single Responsibility Principle (SRP) is the first one in the list. The principles are typically referred to collectively as SOLID, where each letter represents one of the five principles.

• DRY (Don’t Repeat Yourself): The DRY principle promotes the idea of writing code only once and reusing it when necessary. It reduces redundancy, simplifies maintenance, and helps maintain consistency throughout the codebase. For example, rather than duplicating the same validation logic in multiple parts of an application, you can create a reusable validation module.
• KISS (Keep It Simple, Stupid): This principle encourages simplicity in design. It suggests that systems and code should be kept as simple as possible. Simple designs are often easier to understand, maintain, and extend.
• YAGNI (You Ain’t Gonna Need It): YAGNI advises against adding functionality to a system until it is actually required. This principle helps prevent overengineering and keeps the codebase focused on immediate needs.

While the world of software architecture is vast, understanding and applying these architectural patterns and design principles can empower you to construct resilient, maintainable, and adaptable systems, setting the stage for the success of your software projects. As we wrap up this installment, get ready for the next exciting chapter where we’ll explore the realms of Scalability, Performance, and Security in Architecture. Stay tuned for more insightful insights!