On the Interplay of Exception Handling and Design by Contract: An Aspect-Oriented Recovery Approach

Design by Contract (DbC) is a technique for developing and improving functional software correctness through defi- nition of “contracts‿ between client classes and their suppliers. Such contracts are enforced during runtime and if any of them is violated a runtime error should occur. Runtime assertions checkers (RACs) are a well-known technique that enforces such contracts. Although they are largely used to implement the DbC technique in contemporary languages, like Java, studies have shown that characteristics of contem- porary exception handling mechanisms can discard contract violations detected by RACs. As a result, a contract violation may not be reflected in a runtime error, breaking the supporting hypothesis of DbC. This paper presents an error recovery technique for RACs that tackles such limitations. This technique relies on aspect-oriented programming in order to extend the functionalities of existing RACs stop- ping contract violations from being discarded. We applied the recovery technique on top of five Java-based contemporary RACs (i.e., JML/jml, JML/ajml, JContractor, CEAP, and Jose). Preliminary results have shown that the pro- posed technique could actually prevent the contract violations from being discarded regardless of the characteristics of the exception handling code of the target application.