Replacing the Gearbox (while Driving Down the Motorway)
summary
A 12‑year ERP moves from Apache Isis to Apache Causeway (running on Spring Boot) over about two years with roughly 2.5 FTE while still shipping features; code is split into ~160 Maven modules, migrated module-by-module using Maven profiles plus marker files and git worktrees, OpenRewrite automated many API changes, approvals tests lock dependency lists, CI builds V1 and V2 Docker images in parallel for side‑by‑side Kubernetes testing, the migration goes live (June) and works, next big hurdle is JDO → JPA.
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chapters (11)
- 0:00Introduction and project overview
- 5:18Motivation for the upgrade
- 7:27Changing the framework gearbox
- 17:20Git work trees for parallel development
- 26:05Demo: Maven profiles and OpenRewrite
- 31:25Modular monolith structure
- 36:40Dependency management with approval tests
- 43:43Parallel builds and CI pipeline
- 46:52Branch by abstraction and coding conventions
- 49:21Business alignment and go-live
- 50:45Future migrations and conclusion
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