Refactoring Solutions Research Articles

Model‐based source code refactoring with interaction and visual cues

AbstractRefactoring source code involves the developer in a myriad of program detail that can obscure the design changes that they actually wish to bring about. On the other hand, refactoring a UML model of the code makes it easier to focus on the program design, but the burdensome task of applying the refactorings to the source code is left to the developer. In an attempt to obtain the advantages of both approaches, we propose a refactoring approach where the interaction with the developer takes place at the model level, but the actual refactoring occurs on the source code itself. We call this approach model‐based source code refactoring and implement it in this paper using two tools: (1) Design‐Imp enables the developer to use interactive search‐based design exploration to create a UML‐based desired design from an initial design extracted from the source code. It also provides visual cues to improve developer comprehension during the design‐level refactoring process and to help the developer to discern between promising and poor refactoring solutions. (2) Code‐Imp then refactors the original source so that it has the same functional behavior as the original program, and a design close to the one produced in the design exploration phase, that is, a design that has been confirmed as “desirable” by the developer. We evaluated our approach involving interaction and visual cues with industrial developers refactoring three Java projects, comparing it with an approach using interaction without visual cues and a fully automated approach. The results show that our approach yields refactoring sequences that are more acceptable both to the individual developer and to a set of independent expert refactoring evaluators. Furthermore, our approach removed more code smells and was evaluated very positively by the experiment participants.

From Inheritance to Mockito: An Automatic Refactoring Approach

Unit testing focuses on verifying the functions of individual units of a software system. It is challenging due to the high inter dependencies among software units. Developers address this by mocking—replacing the dependency by a “fake” object. Despite the existence of powerful, dedicated mocking frameworks, developers often turn to a “hand-rolled” approach—inheritance. That is, they create a subclass of the dependent class and mock its behavior through method overriding. However, this requires tedious implementation and compromises the design quality of unit tests. This work contributes a fully automated refactoring framework to identify and replace the usage of inheritance by using Mockito—a well received mocking framework. Our approach is built upon the empirical experience from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">five</i> open source projects that use inheritance for mocking. We evaluate our approach on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nine</i> other projects. Results show that our framework is efficient, generally applicable to new datasets, mostly preserves test case behaviors in detecting defects (in the form of mutants), and decouples test code from production code. The qualitative evaluation by experienced developers suggests that the auto-refactoring solutions generated by our framework improve the quality of the unit test cases in various aspects, such as making test conditions more explicit, as well as improved cohesion, readability, understandability, and maintainability with test cases. Finally, we submit 23 pull requests containing our refactoring solutions to the open source projects. It turns our that, 9 requests are accepted/merged, 6 requests are rejected, the remaining requests are pending (5 requests), with unexpected exceptions (2 requests), or undecided (1 request). In particular, among the 21 open source developers that are involved in the reviewing process, 81% give positive votes. This indicates that our refactoring solutions are quite well received by the open source projects and developers.

Software code refactoring based on deep neural network‐based fitness function

SummaryRefactoring is extensively recognized for enhancing the internal structure of object‐oriented software while preserving its external behavior. However, determining refactoring opportunities is challenging for designers and researchers alike. In recent years, machine learning algorithms have shown a great possibility of resolving this issue. This study proposes a deep neural network‐based fitness function (DNNFF) to resolve the software refactoring issue. This study suggests an effective learning technique that automatically featured extracted from the trained models and predicted code clones to recommend which category to refactor. The software engineers automatically assess the recommended refactoring solutions using Genetic Algorithms (GA) for minimum iterations. A Deep Neural Networks (DNN) utilizes these training instances to assess the refactoring solutions for the residual iterations. The refactoring process primarily depends on software designers' skills and perceptions. The simulation findings demonstrate that the suggested DNNFF model enhances the code change score of 98.7%, automatic refactoring score of 97.3%, defect correlation ratio of 96.9%, refactoring precision ratio of 95.9%, flaw detection ratio of 94.4%, and reduces the execution time of 10.2% compared to other existing methods.

Detecting the Locations and Predicting the Maintenance Costs of Compound Architectural Debts

Architectural Technical Debt ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATD</i> ) refers to sub-optimal architectural design in a software system that incurs high maintenance “interest” over time. Previous research revealed that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATD</i> has significant negative impact on daily development. This paper contributes an approach to enable an architect to precisely locate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> , as well as capture the trajectory of maintenance cost on each debt, based on which, predict the cost of the debt in a future release. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> are expressed in four typical patterns, which entail the core of each debt. Furthermore, we aggregate compound <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> to capture the complicated relationship among multiple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATD</i> instances, which should be examined together for effective refactoring solutions. We evaluate our approach on 18 real-world projects. We identified <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">persistently</i> incur significant (up to 95 percent of) maintenance costs in most projects. The maintenance costs on the majority of debts fit into a linear regression model—indicating stable “interest” rate. In five projects, 12.1 to 27.6 percent of debts fit into an exponential model, indicating increasing “interest” rate, which deserve higher priority from architects. The regression models can accurately predict the costs of the majority of (82 to 100 percent) debts in the next release of a system. By aggregating related <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> , architects can focus on a small number of cost-effective compound debts, which contain a relatively small number of source files, but account for a large portion of maintenance costs in their projects. With these capabilities, our approach can help architects make informed decisions regarding whether, where, and how to refactor for eliminating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ATDs</i> in their systems.

Software refactoring side effects

AbstractSoftware refactoring solutions aim at mitigating the negative effects of code and design smells on the overall software quality. Many efforts have been exerted to improve the software refactoring process. However, most of these efforts, despite their contributions, overlooked the side effects of the identified refactoring opportunities that may lead to new smells that will go unnoticed. This paper addresses the side effects of software refactoring and proposes sound solutions for handling them. Unlike current practices in software maintenance, we recommend three different approaches to handle the refactoring side effects. In the first approach, called the baseline, we opt to ignore the smells, caused by refactoring, while executing the identified refactoring decisions. In the second one, refactoring decisions are continually updated to fix all smells caused by side effects. In the last approach, only a subset of these smells is appended to the original smell sequence during the execution of the refactoring decisions. Thanks to the proposed approaches, optimal refactoring decisions are identified using a multi‐objective (MO) optimization algorithm commonly known as the MO covariance matrix adaptation evolution strategy (MO‐CMA‐ES). Experiment results corroborate our assumptions and show the superiority of the second approach over the other ones.

Enabling Decision and Objective Space Exploration for Interactive Multi-Objective Refactoring

Due to the conflicting nature of quality measures, there are always multiple refactoring options to fix quality issues. Thus, interaction with developers is critical to inject their preferences. While several interactive techniques have been proposed, developers still need to examine large numbers of possible refactorings, which makes the interaction time-consuming. Furthermore, existing interactive tools are limited to the ”objective space” to show developers the impacts of refactorings on quality attributes. However, the “decision space” is also important since developers may want to focus on specific code locations. In this paper, we propose an interactive approach that enables developers to pinpoint their preference simultaneously in the objective (quality metrics) and decision (code location) spaces. Developers may be interested in looking at refactoring strategies that can improve a specific quality attribute, such as extendibility (objective space), but such strategies may be related to different code locations (decision space). A plethora of solutions is generated at first using multi-objective search that tries to find the possible trade-offs between quality objectives. Then, an unsupervised learning algorithm clusters the trade-off solutions based on their quality metrics, and another clustering algorithm is applied within each cluster of the objective space to identify solutions related to different code locations. The objective and decision spaces can now be explored more efficiently by the developer, who can give feedback on a smaller number of solutions. This feedback is then used to generate constraints for the optimization process, to focus on the developer's regions of interest in both the decision and objective spaces. A manual validation of selected refactoring solutions by developers confirms that our approach outperforms state of the art refactoring techniques.

An Interactive and Dynamic Search-Based Approach to Software Refactoring Recommendations

Successful software products evolve through a process of continual change. However, this process may weaken the design of the software and make it unnecessarily complex, leading to significantly reduced productivity and increased fault-proneness. Refactoring improves the software design while preserving overall functionality and behavior, and is an important technique in managing the growing complexity of software systems. Most of the existing work on software refactoring uses either an entirely manual or a fully automated approach. Manual refactoring is time-consuming, error-prone and unsuitable for large-scale, radical refactoring. On the other hand, fully automated refactoring yields a static list of refactorings which, when applied, leads to a new and often hard to comprehend design. Furthermore, it is difficult to merge these refactorings with other changes performed in parallel by developers. In this paper, we propose a refactoring recommendation approach that dynamically adapts and interactively suggests refactorings to developers and takes their feedback into consideration. Our approach uses NSGA-II to find a set of good refactoring solutions that improve software quality while minimizing the deviation from the initial design. These refactoring solutions are then analyzed to extract interesting common features between them such as the frequently occurring refactorings in the best non-dominated solutions. Based on this analysis, the refactorings are ranked and suggested to the developer in an interactive fashion as a sequence of transformations. The developer can approve, modify or reject each of the recommended refactorings, and this feedback is then used to update the proposed rankings of recommended refactorings. After a number of introduced code changes and interactions with the developer, the interactive NSGA-II algorithm is executed again on the new modified system to repair the set of refactoring solutions based on the new changes and the feedback received from the developer. We evaluated our approach on a set of eight open source systems and two industrial projects provided by an industrial partner. Statistical analysis of our experiments shows that our dynamic interactive refactoring approach performed significantly better than four existing search-based refactoring techniques and one fully-automated refactoring tool not based on heuristic search.

Recommending Refactoring Solutions Based on Traceability and Code Metrics

Software refactoring has been extensively used to rectify the design flaws and improve software quality without affecting its observable behaviors. For a given code smell, it is common that there exist multiple refactoring solutions. However, it is challenging for developers to select the best one from such potential solutions. Consequently, a number of approaches have been proposed to facilitate the selection. Such approaches compare and select among alternative refactoring solutions based on their impact on metrics of source code. However, their impact on the traceability between source code and requirements is ignored although the importance of such traceability has been well recognized. To this end, we select among alternative refactoring solutions according to how they improve the traceability as well as source code design. To quantify the quality of traceability and source code design we leverage the use of entropy-based and traditional coupling and cohesion metrics respectively. We virtually apply alternative refactoring solutions and measure their effect on the traceability and source code design. The one leading to greatest improvement is recommended. The proposed approach has been evaluated on a well-known data set. The evaluation results suggest that on up to 71% of the cases, developers prefer our recommendation to the traditional recommendation based on code metrics.

On the use of many quality attributes for software refactoring: a many-objective search-based software engineering approach

Search-based software engineering (SBSE) solutions are still not scalable enough to handle high-dimensional objectives space. The majority of existing work treats software engineering problems from a single or bi-objective point of view, where the main goal is to maximize or minimize one or two objectives. However, most software engineering problems are naturally complex in which many conflicting objectives need to be optimized. Software refactoring is one of these problems involving finding a compromise between several quality attributes to improve the quality of the system while preserving the behavior. To this end, we propose a novel representation of the refactoring problem as a many-objective one where every quality attribute to improve is considered as an independent objective to be optimized. In our approach based on the recent NSGA-III algorithm, the refactoring solutions are evaluated using a set of 8 distinct objectives. We evaluated this approach on one industrial project and seven open source systems. We compared our findings to: several other many-objective techniques (IBEA, MOEA/D, GrEA, and DBEA-Eps), an existing multi-objective approach a mono-objective technique and an existing refactoring technique not based on heuristic search. Statistical analysis of our experiments over 31 runs shows the efficiency of our approach.

Improving multi-objective code-smells correction using development history

One of the widely used techniques to improve the quality of software systems is refactoring. Software refactoring improves the internal structure of the system while preserving its external behavior. These two concerns drive the existing approaches to refactoring automation. However, recent studies demonstrated that these concerns are not enough to produce correct and consistent refactoring solutions. In addition to quality improvement and behavior preservation, studies consider, among others, construct semantics preservation and minimization of changes. From another perspective, development history was proven as a powerful source of knowledge in many maintenance tasks. Still, development history is not widely explored in the context of automated software refactoring. In this paper, we use the development history collected from existing software projects to propose new refactoring solutions taking into account context similarity with situations seen in the past. We propose a multi-objective optimization-based approach to find good refactoring sequences that (1) minimize the number of code-smells, and (2) maximize the use of development history while (3) preserving the construct semantics. To this end, we use the non-dominated sorting genetic algorithm (NSGA-II) to find the best trade-offs between these three objectives. We evaluate our approach using a benchmark composed of five medium and large-size open-source systems and four types of code-smells (Blob, spaghetti code, functional decomposition, and data class). Our experimental results show the effectiveness of our approach, compared to three different state-of-the-art approaches, with more than 85% of code-smells fixed and 86% of suggested refactorings semantically coherent when the change history is used.

Prioritizing code-smells correction tasks using chemical reaction optimization

The presence of code-smells increases significantly the cost of maintenance of systems and makes them difficult to change and evolve. To remove code-smells, refactoring operations are used to improve the design of a system by changing its internal structure without altering the external behavior. In large-scale systems, the number of code-smells to fix can be very large and not all of them can be fixed automatically. Thus, the prioritization of the list of code-smells is required based on different criteria such as the risk and importance of classes. However, most of the existing refactoring approaches treat the code-smells to fix with the same importance. In this paper, we propose an approach based on a chemical reaction optimization metaheuristic search to find the suitable refactoring solutions (i.e., sequence of refactoring operations) that maximize the number of fixed riskiest code-smells according to the maintainer's preferences/criteria. We evaluate our approach on five medium- and large-sized open-source systems and seven types of code-smells. Our experimental results show the effectiveness of our approach compared to other existing approaches and three different others metaheuristic searches.

Model refactoring using examples: a search‐based approach

ABSTRACTOne of the important challenges in model‐driven engineering is how to improve the quality of the models' design in order to help designers understand them. Refactoring represents an efficient technique to improve the quality of a design while preserving its behavior. Most of existing work on model refactoring relies on declarative rules to detect refactoring opportunities and to apply the appropriate refactorings. However, a complete specification of refactoring opportunities requires a huge number of rules. In this paper, we consider the refactoring mechanism as a combinatorial optimization problem where the goal is to find good refactoring suggestions starting from a small set of refactoring examples applied to similar contexts. Our approach, named model refactoring by example, takes as input an initial model to refactor, a set of structural metrics calculated on both initial model and models in the base of examples, and a base of refactoring examples extracted from different software systems and generates as output a sequence of refactorings. A solution is defined as a combination of refactoring operations that should maximize as much as possible the structural similarity based on metrics between the initial model and the models in the base of examples. A heuristic method is used to explore the space of possible refactoring solutions. To this end, we used and adapted a genetic algorithm as a global heuristic search. The validation results on different systems of real‐world models taken from open‐source projects confirm the effectiveness of our approach. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Automating extract class refactoring: an improved method and its evaluation

During software evolution the internal structure of the system undergoes continuous modifications. These continuous changes push away the source code from its original design, often reducing its quality, including class cohesion. In this paper we propose a method for automating the Extract Class refactoring. The proposed approach analyzes (structural and semantic) relationships between the methods in a class to identify chains of strongly related methods. The identified method chains are used to define new classes with higher cohesion than the original class, while preserving the overall coupling between the new classes and the classes interacting with the original class. The proposed approach has been first assessed in an artificial scenario in order to calibrate the parameters of the approach. The data was also used to compare the new approach with previous work. Then it has been empirically evaluated on real Blobs from existing open source systems in order to assess how good and useful the proposed refactoring solutions are considered by software engineers and how well the proposed refactorings approximate refactorings done by the original developers. We found that the new approach outperforms a previously proposed approach and that developers find the proposed solutions useful in guiding refactorings.