Research On Legacy Software Migration Based On Source-to-Source Translation

Legacy software is a kind of software systems that are critical components of the users' business systems. These systems have been run many years and continued to be maintained and updated with constantly changed requirements. The shortage of qualified technical staffs and the changing to modern computing environment brings difficulty to software maintenance. One feasible method to solve this problem is to translate legacy source to modern language source. This thesis first makes a comparison between Cobol and Java language, then surveyes some major legacy migration strategies. Based on this analysis, we designed and implemented a language convertor---Cota that translates Cobol source to Java source. In the translator, we developed several techniques to address the problems encountered in Cobol2Java translation such as condition name variables translation, data object model mapping, control flow restructure, dynamic call and file/database access.During that time, an in-depth study was made on data type mapping, control flow restructure and user interface shifting. This thesis proposes answers to these three problems and implements an automatic method to migrate legacy software to target platform with functional equivalence. This paper also presents an optimization method to do multi-precison arithmetic in Cobol2Java translation. Test results show that our method could get a performance speedup of 98% over traditional method in arithmetic intensive programs.We conclude major contributions of this thesis as follow:(1) designed and implemented an automatic Cobol2Java translator, and this translator could be used as a basis platform supporting re-engineering and legacy migration research.(2) designed and implemented a pure Java library that supports Cobol semantics including legacy file access support. It can facilitate Java programmers and Cobol programmers and help to train qualified legacy maintenance staffs. Users could develop business web applications with Cobol functions directly. It can also help to reduce maintenance cost and integration with new applications.(3) presents a new automatic method based on type wrapping to do data type mapping. It supports both low level access and high level access and is important to keep function...