Amsterdam Java User Group

Join in with the latest Amsterdam JUG Meetup at Code Nomads and OpenValue office.

For more details and discussions on the below, go to bit.ly/join-foojay-slack to join the Friends of OpenJDK (Foojay.io) Slack and use the #jug-amsterdam channel for conversations related to the below.

Program:

• 17:00 - Doors Open (And Food!)
• 18:00 - 18:45 Talk 1: Artem Makarov—Hacked in Translation: Reverse Engineering an Abandoned IoT Device
• 19:00 - 19:45 Talk 2: Philipp Fehre—OpenFeature in Production: Introducing Feature Flags at Mollie
• 20:00 - 20:45 Talk 3: Victor Rentea—Event-Based Integration Pitfalls
• 20:45: Networking

Abstracts:

Hacked in translation: Reverse Engineering an Abandoned IoT Device (Artem Makarov)

As everybody knows, "L" in IoT stands for long-term support. I'll take you on a tour of my technical adventure where I revived an abandoned IoT "AI" translator and gave it a new life, 2025-style.

Through deciphering peculiar protocols and formats, reverse engineering firmware and software and doing the necessary research to implement a replacement, we'll see how curiosity and persistence can help you overcome the most obscure technical challenges.

OpenFeature in Production: Introducing Feature Flags at Mollie (Philipp Fehre)

Founded in 2004, in 2023 Mollie made its journey into GCP, and deeper into the Java world. While Mollie has been a user of feature flagging for customers for a long time, with an implementation tied to the monolith, the journey into a multiservice Cloud world was not obvious. Born out of a focus on reliability, feature flags for all services were first introduced mid 2023, with one clear decision early on: to bet on OpenFeature to avoid vendor lock-in. Since then, the infrastructure has evolved and is now fully embracing open source, by self-hosting a flagd based backend.

This is also a story about taking an iterative approach to core infrastructure components, based on lasting decisions: betting on OpenFeature, embracing open source with flagd. Flagd and other backend components have been running in production now for some time, serving as the backend for feature flags for some of Mollie's most critical components in the payment infrastructure.

Event-Based Integration Pitfalls (Victor Rentea)

You publish Events instead of performing REST calls. What can go wrong? Join this tour of the top pitfalls and core patterns of Event-Driven Architectures:

• duplicated messages
• out-of-order
• race bugs
• request-reply
• error handling
• observability
• security
• privacy issues

Collected with love from 150 companies!

Bios:

About Artem. Artem Makarov is a Principal Engineer at Code Nomads. He's been working on Java projects in various industries for the past 14 years. Having Masters in Electronics Engineering he is passionate for applying engineering practices in his projects, contributing to better software design and reliability. In his free time he enjoys traveling, road cycling and learning to play music instruments.

About Philipp. Backend engineer for the almost two decades, normally found in JVM land exploring reliability and infrastructure.

About Victor. With two decades of experience, Victor is a Java Champion and Software Architect who has dedicated his career to inspiring thousands of engineers through intense and entertaining workshops. The lessons he learned from a decade of training at 150+ companies, Victor turned into countless talks at top-rated conferences, where he became known as “the guy with the soundboard”. In his (very little) spare time, he does coaching and consultancy, and organizes online meetups for European Software Crafters, the world’s largest developer community about improving code quality. Discover his training topics at https://victorrentea.ro

Join in with the latest Amsterdam JUG Meetup at Sociale Verzekeringsbank (SVB), Van Heuven Goedhartlaan 1, 1181 KJ Amstelveen, Nederland.

Important notes:

• Bring your passport, or ID card, for identification, otherwise you will not be let in.
• When you register here on the Meetup page, please make sure to include your first and lastname. (If you have not done so, please drop a mail to amsterdamjug@googlegroups.com with your first and lastname.)
• There is free parking, if you send your license plate number to amsterdamjug@googlegroups.com.
• Vegetarian options will be available.
• Signage will be clear, apologies to those who got lost at previous meetups.

For more details and discussions on the below, go to bit.ly/join-foojay-slack to join the Friends of OpenJDK (Foojay.io) Slack and use the #jug-amsterdam channel for conversations related to the below.

In this meetup, in addition to food, drinks, and networking, you will experience the following program and talks:

17:45 - 18:00: Doors Open
18:00 - 18:45: Food (Asian buffet)
18:45 - 19:30 Talk 1: Increasing Portability in a Containerized World (Spoiler: It’s More Than Just Docker)—Jeffrey Janssen (SVB)
19:30 - 20:00 Talk 2: Level Up Your Java Streams with Gatherers—Hinse ter Schuur (SDB Professionals)
20:00 Short Break
20:15 - 20:45 Talk 3: Be More Productive with IntelliJ IDEA—Marit van Dijk (JetBrains)
20:45 - 21:00 Exit

Abstracts

Increasing Portability in a Containerized World (Spoiler: It’s More Than Just Docker)—Jeffrey Janssen (SVB)

When we talk about portability, containers often steal the spotlight. But what happens when you’re migrating an entire DevOps process—from on-prem OpenShift on bare metal and CI/CD pipelines to the cloud? It’s not just about containers: it's about transforming the way your Java applications are built, deployed, and scaled in a cloud-native world.

In this session, I’ll take you through our journey of moving everything to the cloud: setting up cloud-based CI/CD pipelines, using OpenShift in Azure, and automating everything with ArgoCD based on GitOps principles. This talk focuses on the DevOps techniques surrounding Java applications—how to make them portable, how to integrate them into cloud environments, and how to automate the deployment process for faster, more scalable solutions.

If you're a Java developer looking to understand how cloud-native DevOps practices can help automate your workflows and scale your applications, this session is for you.

Level Up Your Java Streams with Gatherers—Hinse ter Schuur (SDB Professionals)

Since Java 8, the Stream API has been a valuable tool for Java developers. However, our hunt for better solutions has often left us wanting more. Until now, we could only use the standard provided intermediate operations on streams, like map, filter, and flatMap.

Enter Java 24's new Stream Gatherers, which allow for adding custom intermediate operations to our streams.

In this session, you'll learn what Gatherers are, where they shine, and how you can implement your own. By the end of the session, you'll be fully equipped to use this powerful new feature in your day-to-day work.

Be More Productive with IntelliJ IDEA—Marit van Dijk (JetBrains)

IntelliJ IDEA is designed to help developers stay in the flow while working. It has a powerful editor, refactorings, navigation, and all kinds of smart features to help you write and read code. At the same time, it is jam packed with tools professional developers need, like Maven, Gradle, Spring, Git, Databases, Test tools and more. And did I mention a fantastic debugger?

In this talk, you will see how IntelliJ IDEA supports your workflow without having to leave the IDE, and learn how you can be a happier and more productive developer.