Understanding the Exception Handling Strategies of Java Libraries: An Empirical Study

This paper presents an empirical study whose goal was to investigate the exception handling strategies adopted by Java libraries and their potential impact on the client applications. In this study, exception flow analysis was used in combination with manual inspections in order: (i) to characterize the exception handling strategies of existing Java libraries from the perspective of their users; and (ii) to identify exception handling anti-patterns. We extended an existing static analysis tool to reason about exception flows and handler actions of 656 Java libraries selected from 145 categories in the Maven Central Repository. The study findings suggest a current trend of a high number of undocumented API runtime exceptions (i.e., @throws in Javadoc) and Unintended Handler problem. Moreover, we could also identify a considerable number of occurrences of exception handling anti-patterns (e.g. Catch and Ignore). Finally, we have also analyzed 647 bug issues of the 7 most popular libraries and identified that 20.71% of the reports are defects related to the problems of the exception strategies and anti-patterns identified in our study. The results of this study point to the need of tools to better understand and document the exception handling behavior of libraries.