Name: Meetup JUG.CY, October 3rd with Marek Dominiak - A Story of a Painful Migration
Start: 2025-10-03T19:00:00+03:00
End: 2025-10-03T22:00:00+03:00
Location: JetBrains Limited

Later this year, Spring Framework 7.0 and Spring Boot 4.0 will be released, along with many related technologies. This is a good time to start thinking about the upgrade process.

We believe that the best way to prepare is by sharing real-world experience with previous upgrades. If you have such experience—or if you’d like to hear more than what is written in release notes or promised in vendor talks about “smooth and easy upgrades”—join us for an open discussion.

*Participation is completely free, but places are limited. Please check in if you plan to attend the meeting; we can't let you into the building if you are not on the list.*

**Agenda for this evening:**

\- Doors open at 18:00
\- Talk will start at 19:00
\- We will have a short break during the talk
\- We will have discussions regarding the talk with networking opportunities after\.
\- We will finish before 22:00 at the office\, but nothing can stop us from continuing somewhere in the cozy bar\.

**Marek Dominiak - A Story of a Painful Migration: Upgrading Java (11→21+) is Easy; Upgrading Spring (4→6) and Hibernate (5→6) is NOT**

In theory, migrating a large application - especially an older monolith - should be straightforward. Java's backward compatibility and tools like **OpenRewrite** promise to ease the process. But is it really that simple? As the old saying, "In theory, theory and practice are the same. In practice, they are not", anyone who has attempted to upgrade a sizable application (with at least 100,000+ lines of code) knows it's a challenging task.

In my talk, I'll share the journey of a real-world application where we upgraded from **Java 11** with **Spring 4**, **Hibernate 5**, **Elasticsearch 5**, and hundreds of related libraries to **Java 21+**, **Spring 6+**, **Hibernate 6+**, and **Elasticsearch 8**. I'll discuss the pain points that required out-of-the-box thinking, rewriting outdated solutions, removing unnecessary code and libraries, and more.

Join me to learn practical solutions that can save you time and pain when migrating your application to a newer stack. Whether you're planning an upgrade or just curious about the process, this talk will provide valuable insights and a bit of fun along the way.

**About the speaker: Marek Dominiak**

I'm a CTO of a software house, a hands-on architect, and a Trainer with 18 years of experience mainly in the Java world. I've spent a lot of time mentoring developers and leading teams, with a big focus on creating sustainable solutions - systems that will last for many years. This set me on the path of learning about Software Craftsmanship, Domain-Driven Design, and code quality early on. Over my career, I've completed many small and large projects that work in production, interviewed developers, handled communication with customers, helped design Architecture for entire systems and delivered them, and introduced many technologies proven in production. I've trained hundreds (550+) of people in modern architecture and testing. I like to share my knowledge at conferences related to software development.

Andrei Kogun

JUG.CY

Technology

Java

Open Source

Software Development

Computer Programming

Java Concurrency

Java Virtual Machine

Meetup JUG.CY, October 3rd with Marek Dominiak - A Story of a Painful Migration

Spring Framework

Hibernate

JetBrains Limited

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Meetup JUG.CY, October 3rd with Marek Dominiak - A Story of a Painful Migration

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