Helidon 27 Introduces Restructured Programming Models and New Messaging and Data Modules

The release of Helidon 27 is the very first that follows the Oracle Tip & Tail Model of Library Development where the Tip adopts the latest Java technology and the Tail provides a more stable and secure baseline. Concurrent with the release of JDK 27, changes include a restructure of the original programming models and introduce two new modules, Helidon Messaging and Helidon Data JDBC.

Helidon 27 serves as the Tip, meaning that: it aligns with JDK 27; adopts the latest Java features; and will continue to be updated under the current OpenJDK release cadence. Therefore, Helidon 28 will be available with the upcoming release of JDK 28 in March 2027.

Helidon 4.5.5, still managed under the familiar Helidon semantic versioning, serves as the Tail, means that: it maintains Helidon 4.5 LTS on its JDK 21 baseline with support for JDK 25; prioritizes critical bugs, security fixes and carefully selected backports; and allows for a longer-lived production baseline for development teams.

Helidon 27 is maintained under the auspices of the Java Verified Portfolio (JVP), an ecosystem of Oracle-supported technologies first introduced at JavaOne 2026, It also includes JavaFX 27, Jipher 20 and the Java Platform Extension Visual Studio Code

Originally named J4C (Java for Cloud), Helidon was designed to be simple and fast, and originally contained two programming models: Helidon SE and Helidon MP. This release introduces the new Helidon Core, replacing Helidon SE, with two new programming models: Imperative and Declarative. As the names imply, Imperative, similar to heritage Helidon SE, allows developers to create their applications using “plain old” Java without dependency injection or annotations. Declarative, on the other hand, provides developers the ability to use dependency injection and annotations that generate imperative code and wiring at build time.

Helidon MicroProfile replaces the heritage Helidon MP and has been moved into its own project. It will continue to support the specifications under MicroProfile and Jakarta EE and follow the Helidon semantic versioning.

Helidon SE Integrations has also been moved to its own project and renamed as Helidon Extensions. Each extension will be independently maintained under their own release lifecycle.

Helidon Messaging, a new messaging layer that simplifies traditional messaging, avoids reactive APIs such as the MicroProfile Reactive Messaging specification. Developers can use ordinary, blocking Java for interoperability with connector-neutral channels, such as Kafka, JMS or Apache Pulsar, that are bound through configuration and pluggable connectors.

Helidon Data JDBC provides a unified API for working with data repository queries that serve as an abstraction over traditional Object–Relational Mapping (ORM). This enables interfaces with query definitions to be translated into implementation classes at compile time. Helidon Data JDBC supports the Jakarta Persistence specification and its corresponding implementations, EclipseLink and Hibernate ORM.

Introduced in September 2018, Helidon SE featured three core APIs to create a microservice -- a web server, configuration, and security -- for building microservices-based applications. Helidon MP implemented various MicroProfile specifications.

Helidon has evolved over the years with the Java community to include support for: GraalVM; Java Persistence Architecture (now Jakarta Persistence); Micronaut Data; Kotlin; MicroStream (now EclipseStore); and IntelliJ IDEA.

Released in June 2020, Helidon 2.0 introduced a web client (to complement the web server) and a database client in Helidon SE and a new command line tool (CLI).

Released in July 2022, Helidon 3.0 delivered: JDK 17 as a minimal version; an implementation of MicroProfile 5.0 and selected Jakarta EE 9.1 specifications; support for JEP 290, Filter Incoming Serialization Data, such that deserialization is disabled by default; an updated Helidon SE routing API; a new project starter; and an updated CLI.

The original Helidon web server, based on Netty, was available in the version 1.0 to 3.0 release trains. A new web server, codenamed Helidon Níma, was based on JEP 444, Virtual Threads, and introduced with the release of Helidon 4.0 in October 2023.

More details on these releases may be found in the release notes for version 27.0.0 and version 4.5.5.