JSON is the go-to format for LLM tool responses, but recent discussions around alternative formats like TOON (Token-Oriented Object Notation) claim potential benefits in token efficiency and performance. While the debate continues—with critical analyses pointing to context-dependent results—the question is: how to experiment with these formats in your own Spring AI applications?

This article demonstrates how to configure Spring AI to convert tool responses between JSON, TOON, XML, CSV, and YAML, enabling you to decide what works best for your specific use case.

Spring AI Tool Calling: A Quick…

In the light of the new major releases of the Spring Framework and Spring Boot, the next major release of the Spring Tools is also around the corner. The GA is scheduled for December 10th and RCs will start to show up from now onwards.

Support for what is new in Spring

Spring Tools 5 contains support for various new features of Spring Framework 7 and Spring Boot 4, ranging from extensive support for the new API versioning feature, support for functional bean definitions via the new bean registrar API, semi-automatic configuration for JSpecify annotation based null analysis and support for AOT…

Hi, Spring fans! Happy Spring Boot 4.0 release day! Make sure to get the bits on the Spring Initializr (you know - start.spring.io)! This release is packed with new features, a lot of which comes from Spring Framework 7. To help break it down for us this week, we’re joined by none other than the legendary Spring Framework contributor Sébastien Deleuze!

This is a new blog post in the Road to GA series, and this time we're taking a look at OpenTelemetry with Spring Boot.

Introduction

In modern cloud native architectures, observability is no longer optional; it is a fundamental requirement. You want to understand what your application is doing via metrics, how requests are flowing through it via traces, and what it is saying via logs.

The OpenTelemetry project, sometimes abbreviated as OTel, provides a vendor-neutral, open-source framework to collect, process, and export telemetry data. Backed by the Cloud Native Computing Foundation, it offers…

This Week in Spring - November 18th, 2025

Hi, Spring fans! I'm thrilled to be in New York City for an exciting week of joint presentations on Spring AI + Bedrock and Spring Boot with the legendary James Ward.

First up: we'll present a workshop at the AI Native Dev Conf today, then speak at the Garden State JUG tonight, then deliver a talk tomorrow at the conference, and finally speak at the New York Java SIG tomorrow night. It might be cold out, but we're bringing the heat!

You know who else is bringing the heat? The Spring team, of course! This past week saw Spring Framework 7 go GA, and with it a whole release train of new releases that will eventually culminate in Spring Boot 4. Once Spring Boot 4 is released, Spring AI, Spring Modulith, and Spring Cloud will all be able to release as well. Watch this space — spring.io/blog — for a ton of new releases this week culminating on the 20th with Spring Boot 4.0.0! (For more on what comes when, check out the Spring Calendar…

Hi, Spring fans! In this installment, I sit down with the legendary Bruce Eckel, who has probably forgotten more about programming languages than I will ever know, and whose book Thinking in Java helped launch me into a career.

This is a new blog post in the Road to GA series, this time sharing an update on the status of the null-safety support across the Spring portfolio, as a follow-up of my previous related blog post Null Safety in Spring applications with JSpecify and NullAway and related Spring I/O talk.

Are we fixing “the billion dollar mistake”?

Yes, we are! And by “we”, I mean the organizations involved in the JSpecify projects, the Spring team, and you, Spring developers who are going to upgrade to Spring Boot 4.

That said, I don’t think “the billion dollar mistake” was the invention of the null reference that Tony Hoare apologized for. I think the real mistake was to not express it explicitly in the type system, as this is the implicit nature of the nullability that causes so many NullPointerException…

The challenge of evaluating Large Language Model (LLM) outputs is critical for notoriously non-deterministic AI applications, especially as they move into production.

Traditional metrics like ROUGE and BLEU fall short when assessing the nuanced, contextual responses that modern LLMs produce. Human evaluation, while accurate, is expensive, slow, and doesn't scale.

Enter LLM-as-a-Judge - a powerful technique that uses LLMs themselves to evaluate the quality of AI-generated content. Research shows that sophisticated judge models can align with human judgment up to 85%, which is actually higher…

Hi, Spring fans! Welcome to another installment of This Week in Spring! As I write this I am preparing for a flight to North Carolina (first in flight!). This week's going to be busy, but next week even busier still! I'll be at AI By The Bay (in San Francisco), AI Native Dev Con (in NYC), and QCon SF (in SF). All in five days! It's going to be a ton of fun but I can't wait.

Why am I so busy? Because Spring's kind of a big thing and it should be and I want to share it. Which brings us to this week's roundup. So, without further ado, let's dive right into it!

• Good news everybody! Spring AI 1.1.0 RC1 is available now!
• yet another amazing post from Spring AI legend Christian Tsolov, this one on using Spring AI and an LLM as a judge
• Spring Boot 4.0.0 RC2 is now available
• Spring Tools 4.32.2 is available now
• in last week's installment of A Bootiful Podcast, I talked to the amazing Vaadin team
• this is so cool! I love it when this sort of stuff happens. thanks to the power of a good framework, optimizations in one place can result in huge improvements across the board!
• Hey, we just released the next set of GAs for Micrometer and Micrometer Tracing! This means that the Boot 4.0 generation's release train has just started. Micrometer 1.16.0 and …