ORACLE ACE · JAVA & MIGRATION ENGINEERING · FLIGHT INSTRUCTOR
Merlin Bögershausen
Making large-scale code migrations
predictable, scalable, and boring.
Enterprise systems age. Teams get stuck.
Between legacy code and modern requirements, teams spend months on migrations that should take weeks — whether it's Spring Boot upgrades, Java version jumps, or framework consolidations. Manual upgrades don't scale. Copy-paste doesn't survive audit. Hope is not a strategy.
Inventory your codebase. Understand what you have before deciding where to go — like a ground check before takeoff.
Recipes, not heroics. Reproducible, testable transformations that work across hundreds of repositories.
Predictable results at scale. Migration Engineering turns modernization from a risky adventure into routine operations.
Talks & Writing
More Action, More Overview – From 4k to 1M Threads
Java's concurrency revolution: Virtual Threads, Scoped Values, and Structured Concurrency in action.
View talk & slides →Release-Train Metro Plan – Dependency Insight for Organizations
Visualizing the hidden coupling in your organization's repositories to enable smarter release planning.
View talk & slides →Enable Digital Sovereignty by Tech Stack Liquidity
How recipe-driven code transformations give organizations real control over their tech stack.
View talk & slides →Kickstart your Migrations – Migration Engineering mit OpenRewrite
From zero to scaled migration: the Migration Engineer's toolkit and methodology.
View talk & slides →Modern Java – Data-Oriented Programming and Beyond
Records, sealed classes, pattern matching, and the features that make Java feel like a modern language.
View talk & slides →OpenRewrite Recipe Development – From Introduction to Deep Dive
Advanced techniques for building custom recipes: imperative visitors, Refaster templates, and testing strategies.
View talk & slides →Let's Get Aware of Accessibility
Why accessibility matters for every developer — and how to start making your applications inclusive.
View talk & slides →Migration Engineering with OpenRewrite
From first inventory to organization-wide rollout: the complete methodology for automated, scalable code migrations.
More Action, More Overview
Java's new concurrency constructs explained — what changes, what breaks, and how to migrate safely.
OpenRewrite Data Tables visualisieren
Using Data Tables to create clarity before, during, and after large-scale migration campaigns.
The Manual
Short, timeless definitions of Migration Engineering concepts. The handbook before the cockpit.
Lossless Semantic Tree (LST)
A fully type-attributed, format-preserving code model that makes automated refactoring safe and precise.
Read entry →Data Table
Structured analysis output from recipe runs — the flight recorder of your migration.
Read entry →Release-Train Metro Plan
A dependency graph visualization that reveals the hidden coupling in your organization's repositories.
Read entry →Recipe
A unit of code transformation — the building block of Migration Engineering.
Read entry →The Migration Instructor
I'm a Staff Software Engineer in the Solutions Engineering team at Moderne Inc with 13+ years of Java experience. I help enterprise teams turn large-scale code migrations from risky adventures into routine operations — using OpenRewrite for reproducible, recipe-driven transformations across hundreds of repositories.
As an Oracle ACE Associate and 2x Javaland Top Speaker, I bring real-world migration experience to the stage at conferences like Devoxx, JFokus, OOP, and Javaland. My talks are rooted in practice from actual customer projects, not sandboxes.
Besides engineering and conferences, I co-organize the JUG Dortmund, teach people to land gliders (yes, I'm a certified Flight Instructor!), and play volleyball.
