We continue the lowdown of Java conferences that took place in the first half of 2025. Last week we explored three Voxxed sessions, this week it's Devoxx Greece, Devoxx UK and JavaOne.

Devoxx Greece was held in Athens, April 10-12:  3 days, 60+ speakers, 70+ sessions, 1200+ attendees.

Numbers speak of its success. Talks aplenty and not just about Java. That being said, a key note on a subject that is ever lasting and concerns all developers, Java savvy or not, is designing REST APIs. As such "Top REST API Design Pitfalls" by Victor Rentea was an eye-opener. It's an entertaining tour of the most common mistakes in designing a REST API: Domain Leakage, Sensitive Data Exposure, Performance issues, CQRS, PUT overload, and breaking changes. Collected with love from over 150 companies.

Another wide-reaching talk, was "Lord of Vulnerabilities: Fellowship of Secure Software Development" by Petros Theocharis. A fun and engaging talk, it uses Lord of the Rings-themed analogies to explore how teams can build secure software using open source frameworks and embrace the best DevSecOps practices.

Back to Java, a trending topic is reducing startup times of the JVM to make Java apps more performant. And one way is through GraalVM. And who is better than Alina Yrenko to talk about it? In her "Bring the Action: Using GraalVM in Production" talk she takes us through all the practical aspects of building and running applications with GraalVM; tooling, monitoring, and using popular libraries. She also covers the most common questions she gets from users.

If Devoxx Greece was a success, then what can be said about Devoxx UK...3days, 120+ speakers, 140+ sessions, taking place in London through May 7 to 9.

The topics covered should have satisfied anyone. For instance on AI, Thomas Vitale in "Concerto for Java and AI" takes us through building production-ready LLM applications by discussing the core architectural patterns for introducing AI capabilities into an existing software system. He explores use cases like text classification, structured data extraction, semantic search, and agent tools.

Still on AI, Sébastien Blanc's "30 minutes to understand MCP (Model Context Protocol)", doesn't just quickly go over its MCP's core concepts but does also show how to consume from a MCP server and how to write one using the Quarkus implementation.

And, these who don't like Gradle (like me) and who are Maven diehards will find the talk "Speed Up Your Maven Build x10… Before You Move to Gradle" by Sergei Chernov very useful. It shows just that; available optimizations that you can leverage, before thinking jumping ship to Gradle.

Finally, to detox from Devoxx, here comes JavaOne. JavaOne is of course Oracle's official event about Java. This year it took place from March 18–20 in Redwood Shores, CA. It featured world-class content including exciting keynotes, expert-led learning sessions and access to the Java community.

The event was lived streamed, but now the sessions have also been uploaded to youtube. Again, lots of interesting stuff, from which we singled out a few.

Of course, on the top of the list had to be the official "Java 24 Launch" which was also the opening keynote. It showcased Java 24's new features and the ways they improve the developers' day to day job.

Immediately after on the ranks, should be Brian Goetz's talk "Where is the Java language going?". In this inspiring talk as a Java language architect he sets the future directions of the language with a focus on project Amber and project Valhalla. If you want an other look of where the language is going from the ecosystem point of view, make sure to check out our "Where's Java going in 2025 ?" which predates the talk.

Finally, an intriguing talk was "SQL, JSON, and Java" by Josh Speigel, member of the Oracle Database group, who looked at how relational databases handle json payloads and subsequently how to use Java to access them from your applications. In detail, the talk covers :

• Trade-offs between storing objects using JSON and a relational model
  
  
• ISO standard SQL for querying JSON
  
  
• Using binary JSON encodings to support low-latency, queryable storage of Java objects with JDBC
  
  
• Integrations with Jackson Databind and Jakarta JSON to avoid string parsing and serialization
  
  
• How new Java 21 features like record patterns complement schema-less, JSON storage

Many more talks to check out. Links to all those aforementioned top talks bellow. For the rest check the associated playlists.

More Information

Devoxx Greece
Top REST API Design Pitfalls

Lord of Vulnerabilities: Fellowship of Secure Software Development

Bring the Action: Using GraalVM in Production

Devoxx UK
Concerto for Java and AI - Building Production-Ready LLM Applications

30 minutes to understand MCP (Model Context Protocol)

Speed Up Your Maven Build x10… Before You Move to Gradle

JavaOne
Java 24 Launch

Where is the Java language going?

SQL, JSON, and Java

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