Strengthening Kotlin for Backend Development: A Strategic Partnership With Spring

At JetBrains, we see Kotlin as a strong foundation for modern backend development, not just because of its technical strengths, but also because of how it helps developers build reliable, maintainable systems more efficiently. As part of our continued efforts to make Kotlin a top choice for professional server-side work, we’re excited to announce a […]

May 22, 2025 - 18:30

Strengthening Kotlin for Backend Development: A Strategic Partnership With Spring

At JetBrains, we see Kotlin as a strong foundation for modern backend development, not just because of its technical strengths, but also because of how it helps developers build reliable, maintainable systems more efficiently. As part of our continued efforts to make Kotlin a top choice for professional server-side work, we’re excited to announce a deepened collaboration between JetBrains and the Spring team.

This strategic partnership covers several key areas that make Kotlin an even more natural and powerful choice for building Spring applications.

As Juergen Hoeller, Spring Framework Co-Founder and Project Lead, and Sébastien Deleuze, Core Committer and Kotlin Support Lead for Spring, put it:

“For many years already, we have heavily embraced Kotlin as a first-class language for Spring applications. We are excited to turn the organic collaboration that has occurred until now into a strategic collaboration between JetBrains and the Spring team to make the Kotlin developer experience with Spring even better!”

Key areas of collaboration

Full null safety for Kotlin and Spring apps
The Spring team is actively working to improve Kotlin support by enhancing null safety across the framework. These improvements will automatically strengthen type safety in your Kotlin code without requiring additional configuration.
Official learning materials in Kotlin
Core Spring learning resources will be made available in Kotlin, helping developers get started more easily and adopt idiomatic Kotlin practices from the start.
Faster Kotlin reflection with kotlinx.reflect
JetBrains is developing a new, faster version of our reflection library – kotlinx.reflect – to improve performance in scenarios that rely heavily on reflection, such as dependency injection and serialization.
Evolving configuration DSLs
The new Bean Registration DSL will provide the foundation for better support for lambda and DSL-based bean definition. This is just the beginning! More announcements are coming soon.

Start using Kotlin with Spring today!

Although some of the improvements announced today are still works in progress, Kotlin is already a fantastic choice for Spring applications.

Kotlin simplifies common backend operations, making code more concise and maintainable. It allows for clear and compact definitions of DTOs, domain models, and mappings (such as of entities to DTOs). With features like named and default parameters, Kotlin removes the need for the builder pattern and other overload-related boilerplate. It also encourages modular design through the use of extension functions and top-level functions.

“Kotlin and Spring Boot is a wonderfully elegant and powerful stack. Just how good modern Spring is becomes more obvious in a modern language,” says Rod Johnson, Spring Framework Original Founder.

On top of that, the Spring team has long supported Kotlin-first features, including:

Coroutines: Spring offers first-class coroutine support for the easier building of reactive applications using structured concurrency.
Kotlin extensions: Spring offers DSLs and extension functions, making your Spring code more expressive and concise.
Configuration DSLs: This feature allows the compiler to help you configure your beans, security, or routes using Spring Kotlin DSLs.

Whether you’re starting a new Kotlin project or gradually adding Kotlin files to an existing Java and Spring codebase, the integration is seamless. Thanks to full interoperability, Kotlin and Java work together natively, allowing you to adopt Kotlin incrementally and on your own terms, even in large projects.

Kotlin with Spring: A growing trend

From startups to global enterprises, Kotlin adoption in the Spring ecosystem has grown rapidly. Teams at companies like Expedia, Atlassian (Jira Software), Mercedes-Benz.io, and many more are already leveraging the combination of Kotlin and Spring for faster development and greater maintainability.

To date, 27% of Spring developers have used Kotlin. This even includes the framework’s original founder, Rod Johnson, as he proudly shared during his talk at KotlinConf 2025.

▶️ Watch a livestream of Rod Johnson’s full talk at KotlinConf 2025 on May 22 at 10:15.

If you’re attending KotlinConf 2025 in Copenhagen, do not miss the Next level Kotlin support in Spring Boot 4 talk by Sébastien Deleuze on May 22. From this session, you can learn more details about the collaboration, as well as the new features intended to improve the developer experience and runtime efficiency of Spring Boot applications for Kotlin developers. The recording of the talk will be available soon after KotlinConf 2025 on the Kotlin YouTube channel.

With this expanded collaboration and the continued Kotlin-first improvements, the number of developers using Kotlin is only set to grow. Kotlin and Spring are better together, and we’re just getting started. With the combined efforts of JetBrains and the Spring team, the next decade of backend development promises to be more productive, more enjoyable, and filled with more Kotlin.

Stay connected with the community!

Want to be the first to get updates about Kotlin for server-side? Join the #server and #spring channels on the Kotlin Slack (if you’re not a member, get your invite first) or subscribe to the main Kotlin news monthly roundup.