The architecture of any software project is one of the most essential components that define its success. Basically, it explicates the key standards, design specifications, development stages, and support regulations of a particular project. Proper software development is always based on standards and technology goals, ensuring the final product is logical, scalable, cost-effective, and aligns with the overall goals and needs of the company.
To create a high-quality application, it’s essential to view its architecture from a variety of standpoints, including principles, standards, patterns, rules of thumb, and practices, which give a full understanding of the project as a whole. Modern software architecture patterns can facilitate the development process but also significantly improve the quality of the final software product and its further performance.
In this article, we’ll review the five essential principles, which are sure to help you in successful application development: Single Responsibility Principle (SRP), Open-Closed Principle (OCP), Liskov Substitution Principle (LSP), Interface Segregation Principle (ISP), and Dependency Inversion Principle (DIP).
Table of Contents:
- What Makes Software Architecture Principles So Important?
- Single Responsibility Principle
- Open-Closed Principle
- Liskov Substitution Principle
- Interface Segregation Principle
- Dependency Inversion Principle
- Are There Any Drawbacks of SOLID?
- Summary
What Makes Software Architecture Principles So Important?
A good software design helps to manage and understand all the stages of product delivery, maximizing its performance with the most relevant design decisions and identifying the potential risks and difficulties you’re likely to deal with. Overall, the most common reasons why software architecture matters are:
- Efficient communication. A well-planned software architecture identifies the communication basis across all its stakeholders (developers, managers, testers, and users), which in turn helps to prioritize concerns, analyze ideas and implement the most effective decisions to improve product performance.
- Robust foundation. The earliest decisions of a software application are the most important, as they become a solid ground for the project’s further development. Additionally, this help to avoid difficulties and add-on expenses as the project moves forward.
- Project scalability. When defined and stable, the software design model can be easily expanded or even re-adjusted to the other projects as well. This benefits not only the project’s cost and delivery timelines but also the ease of troubleshooting and debugging in the existing application.
- Quality & Performance. Software architecture also plays an essential role in improving the existing code quality, making the product more powerful, responsive, and adaptive. Moreover, you can benefit from further app maintenance, which is essential for fixing bugs and anomalies, as well as implementing the add-on functionality.
- Facilitated Development. Last but not least, robust architecting results in better risk management, reduced time to market, reduced complexity, and faster changes deployment, which is exceptionally important for aligning with all the business goals and needs.
Now that you’ve uncovered the major benefits of deploying software architecture in accordance with the selected principles, it’s time to review the five types of architecture principles which are commonly implemented today.
Single Responsibility Principle (SRP)
First, the ‘S” principle in SOLID is SRP (Single Responsibility Principle,) according to which each system unit (for instance, a service, module, class, function, or API) should have only one responsibility and as such one reason to change. Further, the elements of that responsibility should be encapsulated by the responsible class rather than spread out in unrelated classes.
By keeping the responsibilities narrow, it becomes much easier to implement a particular software unit and prevent unexpected side effects related to its further modifications or changes. As a result, you’ll see fewer instances of code smells, improving the code quality and maintainability.
Major SRP Benefits to Know:
- Simplifies the software implementation process;
- Helps to avoid code issues and other side effects of future changes;
- Makes the components easier to explain, understand and implement rather than the all-size-fits-one software units;
- Reduces the probability that you need to change the class;
- Lowers the complexity of each change due to the reduced number of dependent classes affected by those adjustments.
A simple and quite easy-to-understand example of the SRP concept is the Java Persistence API (JPA) specification, the only responsibility of which is to define a standardized way to manage data persisted in a relational database through the object-relational mapping approach.
Open-Closed Principle (OCP)
Being one of the “most important principles of object-oriented design” according to Robert C. Martin, the OCP offers to open the software entities for extension but closed for modification. In other words, it allows adding new functionality without changing the structure of the source code. So, any new class may use it as a parent in its original structure.
Overall, the Open/Closed principle allows for preventing situations in which a change of your class requires modifying all the classes depending on the prior. At the same time, this methodology allows the extension of the software’s functionality on top of inherited basic features.
Major OCP Benefits to Know:
- Provides the add-on level of abstraction which enables loose coupling;
- Allows developers to design and write code with new functionality at minimal changes to the source module;
- Interface modules have zero dependencies on each other, which adds to their flexibility;
- Easy to test and less error-prone.
A common example of using the OCP development approach is the app solution designed to control different types of smart gadgets. Within its interface, the system has a bunch of implementations covered, each of which will regulate the functions of a particular item in it. The only thing you need to do is to install the new implementation to a superclass.
Liskov Substitution Principle (LSP)
The 3rd ‘L’ rule offered in the SOLID design principle is the Liskov Substitution principle or LSP, which basically extends the prior one covered in the previous paragraph. Simply put, this concept defines that objects of a superclass should be interchangeable with objects of its subclasses without breaking the app code. This can be achieved if the objects of subclasses operate similarly to the objects of the superclass.
The core point to know about this software architecture principle is that in this case the behavior of your classes is prioritized higher than the structure. To achieve that, developers should apply at least the same rules to all output parameters as applied to the superclass. Also, it’s important to mind the validation rules on input parameters: these shouldn’t be stricter than the ones implemented by the superclass.
Major LSP Benefits to Know:
- Helps in building good inheritance hierarchies;
- Prevents old codebase from breaking due to the new code;
- Allows swapping the parent and child classes without breaking the code.
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Interface Segregation Principle (ISP)
The Interface Segregation Principle, also known as ISP, is quite similar to the Similar Responsibility Principle. Its key goal is to reduce the side effects and frequency of required changes by splitting the application into multiple, independent components. In turn, this results in less bloated interfaces that outline methods for multiple responsibilities.
While building an interface, developers usually suggest segregating the classes with different sets of behaviors to create multiple interfaces with a specific role for each.
Major ISP Benefits to Know:
- Minimizes frequency of issues and changes;
- Ensures small, focused, and highly cohesive software components;
- Helps to avoid embedding too many exceptions;
- Enables the creation of more client-specific instead of monolithic and bigger interfaces.
The ISP method in the app development architecture is typically applied for creating multiple interfaces within a single application. For instance, in the eCommerce app segment, developers can integrate interfaces for product order and checkout, which are independent and won’t be affected if any of them is changed.
Dependency Inversion Principle (DIP)
Last but not least popular of the SOLID principles is the Dependency Inversion principle, which is mainly designed for building more maintainable and scalable code through loose coupling between components. In other words, it offers to rely on abstractions instead of depending on concretions.
With this approach, the dependency mechanism is based on the interfaces or summary functions and training. So, more general components depend upon lower-stage modules, which in turn depend on lower-level modules and so forth.
Major DIP Benefits to Know:
- Allows decoupling the in-app components;
- Makes the code more flexible, maintainable, testable, and reusable;
- Facilitates the class extension;
- Reduces boilerplate code.
In software development, the structure of higher-level classes doesn’t depend on the lower-level classes, but instead, both depend on abstractions. Additionally, lower-level classes implement an interface defined by the higher-level class, so that the latter doesn’t need to change when the new implementation arrived.
A great yet simple-to-understand example will be a copywriting application, which is based on ‘reader’ and ‘creator’ interfaces defined by itself. Basically, the program will have zero dependence on reading from the keyboard/reading from the scanner or writing to text files/writing to the database, etc, which means developers won’t need to change the program when the new requirement (in our case, for instance, the functionality) comes and remains independent.
Are There Any Drawbacks of SOLID?
Talking about the possible challenges of SOLID principles, there are several key points to know about:
- Testability. First of all, the testability of each module individually becomes more challenging and requires involving the right expertise
- Parallel development. Working on several features at a time surely speeds up product development. However, it is also trickier compared to the consequent approach, in which the system units are designed one by one.
- Module changes. Typically, the change in one module can lead to the modification of other units, which can make the development process more durable than anticipated.
Nevertheless, with the right team of experienced development professionals, these downsides of SOLID principles are minimized and have little to no impact on the development progress, as well as the quality of the final product.
Summary: Are SOLID Principles Worth It?
Being one of the most popular development principles today, SOLID rules provide a solid ground for creating high-quality software systems. Not only can it simplify the entire development process and improve the performance of your decision-making but also allow you to structure your development team and successfully achieve the goals of your business.
As you can see from our review, the SOLID principle can reduce the dependencies of the system’s blocks, making the design process easier and more understandable. Additionally, a SOLID-based code is more maintainable, testable, scalable, and reusable, which is essential for any development project.
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