Amsterdam Java User Group

About Haoyi Li. Haoyi graduated from MIT, has built infrastructure for high-growth companies like Dropbox and Databricks, and has been a major contributor to the open source community with a focus on JVM developer tools. Haoyi has deep experience in the JVM and related technologies, and has used it professionally to build cloud infrastructure, distributed backend systems, programming languages, high-performance web applications, and much more.

This Amsterdam JUG meetup will be hosted and sponsored by JetBrains, in their office at Terrace Tower, Gelrestraat 16, 1079 MZ Amsterdam. The Event Space is located on the 3rd floor.

Agenda

• 18:00 Doors open, food, and welcome to JetBrains!
• 18:30 Talk 1: Anton Arhipov and Daniil Tsarev (JetBrains) presenting “See Through Spring in IntelliJ IDEA”
• 19:15 Break
• 19:20 Talk 2: Tom Cools (Timefold) presenting “LLMs Can't Optimize Schedules, But AI Can!”
• 19:50 Talk 3: Rijo Sam (ABN AMRO) presenting "Java Beyond Frameworks: Avoiding Lock-In with Agnostic Design"
• 20:20 Break
• 20:30 Talk 4: by Kadi McKean and Charlie Jones (ReversingLabs) presenting "Navigating Compliance: What Developers Can Learn From Driving"
• 21:00 End

Information about the talks:

Talk 1: "See Through Spring in IntelliJ IDEA" by Anton Arhipov and Daniil Tsarev (JetBrains)

Some developers say Spring Boot is magic—but it's not. It's a well-structured, ergonomic framework that takes care of the heavy lifting so you can focus on what matters. But when things don't behave as expected, understanding why can be a challenge.

That's where the Spring Debugger in IntelliJ IDEA comes in.

With Spring Debugger, you get deep, real-time insights into your running application, right inside your IDE. No more digging through logs or guessing what's happening under the hood.

Find answers to questions like:

• Where does this property value come from? Is it overridden somewhere?
• Why is this bean being injected, and which candidate was chosen?
• Is there an active transaction? Who started it?
• Which database is my app connected to? Can I explore it with one click?
• How was this value resolved from profiles, config files, or environment variables?

All the context you need is right there, connected to your code, easy to follow, and just a click away.

You will learn how the Spring debugging support in IntelliJ IDEA helps to gain clarity, troubleshoot issues faster, and turn Spring Boot's inner workings into an open book.

Talk 2: “LLMs Can't Optimize Schedules, But AI Can!" by Tom Cools (Timefold)

LLMs have made remarkable progress, which might suggest they're the answer to everything. However, when it comes to everyday tasks like creating work schedules they tend to fall short. As a result, humans often end up creating a schedule manually, which is usually far from optimal.

Fortunately, there’s a lesser-known branch of AI that excels at complex scheduling. In this talk, we’ll discuss Timefold, a Java based open-source AI solver, and you'll discover how it leverages magic (aka math) to generate optimized schedules.

With a series of live demos, you’ll see this form of AI in action and walk away equipped with a powerful new tool for your problem-solving toolbox.

Talk 3: “Java Beyond Frameworks: Avoiding Lock-In with Agnostic Design" by Rijo Sam (ABN AMRO)

The Problem: Modern Java applications often become prisoners of their frameworks. While tools like Spring Boot and Quarkus accelerate development, they create hidden costs: vendor lock-in, bloated dependencies and rigid architectures. What happens when your project outgrows your framework—or a new, better tool emerges?

The Solution: This talk introduces a layered approach to Java development, isolating framework dependencies while keeping core logic pure with Java and Jakarta EE.

Through examples, you’ll see:

1. How to decouple business logic using JSR standards
2. Strategies to replace framework-specific annotations
3. Cloud integration without framework coupling.

Trade-Offs: Yes, this demands more upfront effort—writing custom persistence layers, rigorous tests, and meticulous docs. But the payoff is code that’s adaptable, testable, and maintainable across frameworks, teams, and decades.

Key Takeaways:

1. Practical patterns for agnostic design.
2. When (and when not) to adopt this approach.
3. Tools to ease the transition.

Join me to rethink Java development: less framework magic, more future-proof code.

Talk 4: “Navigating Compliance: What Developers Can Learn From Driving" by Kadi McKean and Charlie Jones (ReversingLabs)

When driving on a highway, you have to follow the rules of the road. You need a valid license, stick to the speed limit, signal when changing lanes, and stop at red lights to ensure safety for everyone. Skipping these steps risks crashes, fines, and sometimes, jail time.

In open source development, compliance with government regulations is a detour, slowing innovation and creativity. But just like a busy highway, these rules exist to keep us safe, organized, and moving toward our destinations. In this talk, we’ll explore the parallels between the rules of the road and software compliance and how all rules are created equally.

Shedding light on how understanding and adhering to regulatory requirements can empower developers rather than hinder them.

We’ll delve into key government mandates shaping the software landscape, from cybersecurity frameworks to supply chain transparency. We’ll also discuss how ignoring compliance can lead to “accidents” like data breaches and legal penalties and how proactive adoption can create a smoother, safer, and least costly route for innovation.

This Amsterdam JUG meetup will be hosted and sponsored by Snowflake, in their office at Gustav Mahlerlaan 300-314, 1082 ME Amsterdam. The Event Space is located on the 3rd floor.

Agenda

• 18:00 Doors open, food, and welcome to Snowflake!
• 18:30 Talk 1: Soroosh Khodami (Code Nomads) presenting “Are We Ready For The Next Cyber Security Crisis Like Log4Shell?”
• 19:15 Break
• 19:30 Talk 2: Danica Fine (Snowflake) presenting “A Fearless Introduction to Apache Iceberg”
• 20:15 Break
• 20:30 Talk 3: Simone Romani (ING) presenting "More Code Confidence with Mutation Testing"
• 21:15 Networking
• 21:30 End

Information about the talks:

Talk 1: “Are We Ready For The Next Cyber Security Crisis Like Log4Shell?” by Soroosh Khodami (Code Nomads)

In a world where vulnerabilities like Log4J, Spring4Shell, and the XZ Backdoor make headlines, securing our software ecosystem has never been more critical.

In this session, Soroosh, a hands-on solution architect with experience working on security platform services for large enterprises like Rabobank, will share practical strategies and best practices for securing the software development process, applicable to both small startups and large organizations.

Key questions that will be answered in this session:

• Can basic SQL Injection threats extend beyond accessing a database server within a restricted network?
• What is a "Supply Chain Attack," and how dangerous can it be?
• What are the most effective low-hanging practices to secure your CI/CD process?
• Shift-Left Security & DevSecOps? What’s the hype, and how is it going to redefine the way we build software?
• How can Software Bill of Materials (SBOM) help us prepare for the next Log4Shell crisis?
• What do EU supply chain security-related regulations (DORA/CRA) mean for developers?

Talk 2: “A Fearless Introduction to Apache Iceberg" by Danica Fine (Snowflake)

New to Apache Iceberg or just starting to test the waters? Time to take the plunge! In this beginner-friendly session, we’ll introduce you to the core features of this high-performance table format and what it has to offer your data team as you build out your modern data lakehouse.

We’ll start by exploring where Iceberg fits within the context of data warehouses, data lakes, and other data storage formats. From there, you’ll be introduced to some of Iceberg’s key features, like schema evolution, hidden partitioning, and ACID-compliant transactions. Next, we’ll dive beneath the surface and explore the open-source tools, query engines, and catalogs that make up the Iceberg ecosystem. We won’t stop there, though! Together, we’ll dive deeper to learn the inner workings of Iceberg when you interact with and maintain your data over time.

By the end of the session, you’ll have the foundation you need to get started applying Iceberg to solve your own data challenges. So come along, and we’ll take the polar plunge together!

Talk 3: "More Code Confidence with Mutation Testing" by Simone Romani (ING)

One of the best ways to assess if code is resilient against bugs is to break it on purpose and see how it reacts. The reaction should be a failure in the tests. If there is no reaction, it means that the tests are not effective enough, meaning their assertions are broad and imprecise.

Mutation testing comes to the rescue for this specific challenge. This methodology changes the source code and then runs the unit tests against the mutated codebase. The generated report helps the engineer find where the weak spots in the tests are.

In this talk, we will cover the theory behind this methodology, followed by a live demo where code which could be described as "100% tested" would still be subject to bugs and how its related tests can be improved. This approach will offer a way for engineers to gain confidence in their code and especially in their tests. With a high test strength, source code will not only be strong but also malleable to modifications, with the safe guardrails of unit tests protecting them from introducing bugs.

You will learn how to write more efficient and resilient tests due to the mutation tests giving them a different perspective on their code quality, compared to the normal tests. Mutation testing will also drive better production code, following the principle of Test Driven Design.