Extracting reusable services from legacy object-oriented systems

Migrating legacy object-oriented system functionalities to SOA environment is a important problem that frequently arises in many system maintenance and integration tasks. A service is often implemented by complex collaborations of many objects in an object-oriented system. Such complexity brings impedance mismatch between service and object. Moreover, the delocalized nature of object-oriented system, where the code associated with a service is distributed across many interrelated objects, make this problem even more challenging. This paper presents a four-staged approach that extracts services from legacy object-oriented systems with source code and documents. In the first stage source code of legacy system is loaded and preprocessed to form different modules according to the explicit dependencies among classes. While preprocessing, some aspect code is also embedded to intercept and log execution traces of system as well as to store states of involved objects. In the second stage, services, which represent system-level business functionalities, are modeled with use cases. Useful test cases are in turn generated from these use cases to identify services. In the third stage, the modularized and intercepted system is executed driven by generated test cases and the execution logs and object states are recorded. In the last stage, services are located and extracted by analyzing the execution logs and restoring the object states. The approach is supported by an integrated tool and the evaluation on five open-source systems yields encouraging result and demonstrates the practical applicability of the approach.