What is Refactoring in Software Engineering?
Updated on January 11, 2023 | by Louise Simon
According to the “father” of refactoring, Martin Fowler: “Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure.”
While refactoring is applicable for any programming language, most modern refactoring tools were created for the Java programming language. In 2001, automated refactoring tools like IntelliJ IDEA Java IDE (Integrated Development Environment), Instantiation’s factor stand-alone refactoring tool, and X-ref plug-in tool for the EMACS editor began to surface in earnest.
What is Refactoring?
Refactoring in software engineering is defined as a methodical process of improving existing computer code without introducing new functionality or altering the code’s external behavior. It changes the definition of code, implementation, and structure without affecting the software’s functioning. It increases the flexibility, maintainability, and readability of software without compromising its functionality.
Refactoring is a continuous process of restructuring program code down to the most basic or simplest design. The word simplest in a refactoring process is determined by the following criteria, in the following order:
- All unit tests are executed
- Clear communication of code for the design concept
- No repetition in the code (duplicated code or logic)
In accordance with the preceding guidelines, the code comprises the fewest number of classes and methods possible.
Types of Refactoring in Software Engineering
This is the refactoring of programming source code, also known as refactoring. Encapsulate Field, Rename Method, Extract Class, Pushdown method, and Introduce Assertion are examples of code refactoring.
It is the process of reorganizing a database. A database refactoring is a simple modification to a database schema that enhances its design while maintaining its behavioral and informational meanings. Renaming a column, moving a method to the database, splitting a table, replacing a LOB with a table, using an official data source, and introducing a column constraint are all examples of database refactoring.
User Interface Refactoring:
A UI refactoring is a simple adjustment to the UI that keeps the semantics intact. Align entry fields, use a standard font, use common button size, indicate the format, reword in active voice, and increase color contrast are some examples of UI refactoring.
Advantages of Code Refactoring
The key reasons to adopt the refactoring approach are:
- Enhances software design
- Improves the readability of software
- Helps in the discovery of bugs
- Allows you to program more quickly
Refactoring can help improve the design of existing code, but it does not replace design building before developing code. It reduces the code size and restructures the confusing code into a simpler one. This significantly improves maintainability, which is necessary because requirements are constantly changing.
Another advantage of refactoring in software engineering is that it changes the way a developer thinks about implementation. The primary goal of implementing a solution is to get it to pass its developer tests in the simplest way possible. The solution’s design can then be analyzed and refactored separately. It can be liberating for a developer to only focus on writing code that causes a test to pass and then individually focus on enhancing that code.
When is Refactoring Required?
There are several reasons why a specific module of code should be refactored, like:
1. Code Smell:
These are indicators of a significant problem in the code which may interfere with development, maintenance, and system performance. Some examples are:
- The presence of duplicate or redundant code
- Code design is overly complicated
- A variable that has been declared but is not used anywhere else in the code
- The presence of too many conditions and loops that may be reduced and simplified
- Code class that does too little and does not justify the class’s existence. Such classes are called lazy classes or freeloaders
- Code is written in such a way that a change in one place necessitates a change in all other locations as well
2. Technical Debt:
In software development, technical debt refers to the additional rework or overhead necessary to implement suitable changes or do things the ‘correct way.’ Legacy systems accumulate significant technical debt over time, making the application prone to failure and difficult to support and maintain.
3. Follow the Agile Software Development Approach:
Agile methodology promotes incremental progress. Without clean, well-structured, and easy-to-maintain code, teams would be unable to enhance existing code with each iteration. If changes are made to the code without sufficient refactoring, they may contribute to code smell or technical debt.
There are several methods and techniques for refactoring code. Let’s have a look at a few other popular ones:
Red Green Refactoring:
It is the most popular and commonly used in the Agile software development process. This strategy adheres to the “test-first” approach to design and implementation, laying the groundwork for all types of refactoring. It is completed in three distinct steps.
- Red: The first step is to write the failed “red-test.” You come to a halt and assess what needs to be developed.
- Green: In the second step, you write the simplest code possible and ensure that the development passes “green” testing.
- Refactoring: In the third and final steps, you focus on refining and enhancing your code while maintaining your test green.
It is primarily used in scenarios where long methods are used in the programs. In this approach, we use streamline procedures to reduce code duplication. Examples include: extract method, inline Temp, extract a variable, replace Temp with Query, inline method, split temporary variable, and so forth.
- Extraction: To discover and extract fragmentation, the code is divided into smaller bits for extraction. Following that, distinct methods for these pieces are constructed, replaced by a call to this new method. Class, local variables, and interface are all used in the extraction process.
- Inline: This strategy reduces the number of methods in the program that are superfluous. All the calls to the methods are detected and replaced with the method’s content. The technique is then removed from the program.
This approach is commonly used for the reduction of redundant code. Class inheritances, new classes and interfaces, hierarchy, the replacement of inheritance with delegation, extraction, and vice versa are all involved.
The best example of this methodology is the pull-up/push-down method.
- Pull-Up method: This method pulls code pieces into a superclass to help eliminate code duplication.
- Push-Down method: This method moves code from a superclass down into the subclasses.
Essentially, under this technique, we create an abstraction layer for the elements of the system that need to be refactored, as well as the counterpart that will eventually replace it. Two frequent instances are provided below:
- Encapsulated field: We force the code to use getter and setter methods to access the field.
- Generalize type: We develop more general types to allow code sharing, to replace type-checking code with states, to replace conditional with polymorphism, and so on.
The Bottom Line
Refactoring is now a crucial part of application modernization and the transition of legacy apps from monolithic to microservices. A clean and well-organized code is always simple to alter, understand, and maintain. If a software developer pays attention to the code refactoring process early on, they will avoid problems later.
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