Migrations · 01 · COBOL → Java
← All migrationsCOBOL to Java
The same business rules, in code your next team can actually read.
Your logic stays. The language changes.
Decades of business rules sit in COBOL programs that fewer and fewer people can maintain. We convert them to Java on Spring Boot and PostgreSQL. Not a line-by-line translation, but code shaped like your domain, and for each module a test set that compares the result with the original.
What you can expect
01
Readable Java
Services, records and methods named after your domain. No COBOL in Java syntax that nobody wants to maintain.
02
Traceable to the source
Every Java class points to the program and paragraph it came from.
03
Arithmetic to the cent
Packed decimals and rounding rules become fixed-scale BigDecimal, and the results are compared with those of the original.
What becomes what
| COBOL / mainframe | Java platform | Point of attention |
|---|---|---|
| Program and paragraphs (PERFORM) | Service classes and methods | Structure follows the domain, not the source file |
| Copybook (01 levels, PIC) | Java records | One definition, shared by service and API |
| COMP-3 / packed decimal | Fixed-scale BigDecimal | Rounding and overflow tested against the original |
| CICS transaction | REST endpoint with a service transaction | Commit and rollback boundaries stay the same |
| JCL job and steps | Scheduled batch job with steps | Restartable from the failed step |
| VSAM KSDS or DB2 table | PostgreSQL table with key and constraints | Access paths become indexes |
| SORT / MERGE | SQL ORDER BY or Java streams | Collating order EBCDIC versus Unicode checked |
| Abends and return codes | Exceptions and error codes in the API | Same failure paths, clearer message |
How we do it
01Analysis
Inventory and dependencies
Which program calls which program, reads which file and runs in which job.
Dead code and duplicates
What no longer runs is not migrated. You decide from a list.
02Conversion
AI-assisted, reviewed by people
AI does the first translation pass and documents the rules. Our developers review and restructure.
Module by module
Each module is converted, tested and delivered on its own.
03Proof
Equivalence tests
The same input through COBOL and Java, output compared field by field.
Parallel run
Before cutover, old and new run side by side on production data.
■Java LTS · Spring Boot
■PostgreSQL · version-controlled schema migrations
■REST API per migrated module
■Test set per converted module
Curious what is inside your COBOL?
We start with an inventory.Start the conversation →