Studying the evolution of exception handling anti-patterns in a long-lived large-scale project

Abstract

Exception handling is a well-known technique used to improve software robustness. However, recent studies report that developers typically neglect exception handling (mostly novice ones). We believe the quality of exception handling code in a software project is directly affected (i) by the absence, or lack of awareness, of an explicit exception handling policy and guidelines and (ii) by a silent rising of exception handling anti-patterns. In this paper, we investigate this phenomenon in a case study of a long-lived large-scale Java Web system in a Public Education Institution, trying to better understand the relationship between (i) and (ii), and the impact of developers' turnover, skills, and guidance in (ii). Our case study takes into account the technical and human aspects. As a first step, we surveyed 21 developers regarding their perception of exception handling in the system's institution. Next, we analysed the evolution of exception handling anti-patterns across 15 releases of the target system. We conducted a semi-structured interview with three senior software engineers, representatives of the development team, to present partial results of the case and raise possible causes for the found problems. The interviewed professionals and a second analysis of the code identified the high team turnover as the source of this phenomenon, since the public procurement process for hiring new developers has mostly attracted novice ones. These findings suggest that the absence of an explicit exception handling policy impacts negatively in the developers' perception and implementation of exception handling. Furthermore, the absence of such policy has been leading developers to replicate existing anti-patterns and spread them through new features added during system evolution. We also observed that most developers have low skills regarding exception handling in general and low knowledge regarding the design and implementation of exception handling in the system. The system maintainer now has a diagnosis of the major causes of the quality problems in the exception handling code and was able to lead the required measures to repair this technical debt.