Success­ful COBOL Java migration
at SüdLea­sing GmbH

SüdLea­sing GmbH is one of the largest leasing compa­nies in Germany and opera­tes within the LBBW Group. The company is an experi­en­ced and compe­tent partner for all aspects of invest­ment finan­cing with a leasing portfo­lio of €3.6 billion. Four hundred employees work at 21 locati­ons throughout Germany. This makes SüdLea­sing GmbH one of the top three leasing compa­nies in Germany.

On the way to a future-proof manage­ment system for leasing contracts

So far, SüdLeasing’s leasing contracts have been proces­sed using a complex COBOL system. It consis­ted of 4,027 programs and copybooks with appro­xi­mately 3.2 million lines of code. In 2019, SüdLea­sing decided to start the “LEASCO Techni­cal Reengi­nee­ring Inven­tory System” project. The aim was to replace the COBOL programming language and to obtain a sustainable system for managing leasing contracts – while comply­ing with all quality speci­fi­ca­ti­ons in an agile project. COBOL should be repla­ced by Java through a tool-based conversion.

Success­ful language conver­sion using sophisti­ca­ted tools

Language conver­sion is the most challen­ging part of a software migration. It cannot succeed without sophisti­ca­ted conver­sion tools based on compi­ler construc­tion techni­ques. The scien­ti­fic approach guaran­tees the seman­tic equiva­lence between origi­nal and conver­ted programs. Exper­tise in compi­ler construc­tion is there­fore an important prere­qui­site for project success. With our COBOL to Java Conver­ter (CoJaC) we have  a mature tool chain for language conver­sion that has proven itself in the present project.

The user inter­face of the COBOL system was develo­ped in-house by SüdLea­sing on a Windows basis with around 2,100 ASCII masks. COBOL server and Windows client exchan­ged their infor­ma­tion via COBOL messages. Even before the start of the migration project, SüdLea­sing redeve­lo­ped the user inter­face as a web appli­ca­tion using the Angular frame­work. The exchange of infor­ma­tion with the unchan­ged COBOL programs conti­nued to take place via COBOL messages. The web appli­ca­tion should conti­nue to be used after the moder­niz­a­tion. The task in the project was to develop an inter­face between the existing web appli­ca­tion and the newly conver­ted Java programs. During the migration, Java web services are created from COBOL servers. The exchange of infor­ma­tion with the web inter­face takes place via Java classes, which were created by conver­ting the COBOL messages. Thus, the web inter­face could be used in paral­lel in the COBOL system and in the Java system during the project period.

Reduced test effort through automa­ted tests

A challenge in every migration project is to prove that the origi­nal and conver­ted programs work identi­cally. The compa­ti­bi­lity of the user inter­face with the origi­nal COBOL system and the genera­ted Java system was used for these tests. A complex collec­tion of Gherkin test scena­rios was created using the Cucum­ber frame­work and control­led by Jenkins. Both the COBOL system and the migra­ted Java system were execu­ted browser-based via Selenium. The results were compa­red. The automa­tic compa­ri­son of the COBOL and Java systems signi­fi­cantly reduced the testing effort.

The project was reali­zed jointly by SüdLea­sing and us using our techno­lo­gies and tools. As planned, the project duration was 1.5 years. The new system is based on a modern Spring archi­tec­ture. The genera­ted Java code is maintainable and perfor­mant. Effici­ent mainten­ance and further develo­p­ment with frame­works such as Maven, Jenkins and Cucum­ber are there­fore possi­ble. The success of the project has again confir­med that software migration is an alter­na­tive to new develo­p­ment and the use of standard software.

Sebas­tian Seek
Head of Software Development
SüdLea­sing GmbH


“Of course, we also feel the pressure in the area of digita­li­sa­tion in our indus­try. In order to be able to conti­nue to offer our innova­tive soluti­ons on the market in the future, it was very important for us to moder­nise our central leasing system. At the begin­ning, we were scepti­cal about the tool-suppor­­ted COBOL-Java migration, since we had heard about projects that had failed. However, we found the right partner in the pro et con team. As early as the proof of concept, it was possi­ble to prove that the complex arith­me­tic opera­ti­ons of finan­cial mathe­ma­tics were carried out correctly and that the runtime for mass proces­sing programs also met our expec­ta­ti­ons. This very positive impres­sion was confir­med as the project progressed.”

“I am proud that pro et con GmbH was once again able to show the poten­tial of our tool-suppor­­ted migration approach in this project. Our COBOL to Java Conver­ter (CoJaC) is a mature tool for this purpose. Such a project is always a joint project between equal partners. Especially in the test phase, which is very important, SüdLea­sing GmbH made a signi­fi­cant contri­bu­tion to the success of the project with its agile approach and the consis­tent use of automa­tic tests. I would like to thank Mr Seek and the entire SüdLea­sing team for the trust they have placed in us. I am sure that with our scien­ti­fic migration approach we can support other compa­nies in success­fully imple­men­ting their digita­li­sa­tion strategies.”

Prof. Dr Uwe Kaiser
Managing Direc­tor of
pro et con GmbH