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Introducing Helidon

What is Helidon?

Helidon is a collection of Java libraries for writing microservices that run on a fast web core powered by Netty. It’s small, fast, and fun to use.

Helidon is open source under the Apache 2.0 license. Sources are available on GitHub.

Helidon is cloud-native ready. It provides fast start-up time and has low memory consumption and a small disk footprint. It also comes with a full observability stack out of the box including health checks, metrics, tracing and logging.

Helidon fully supports GraalVM native image allowing you to build a native executable from your Java application.

Helidon Flavors

Helidon comes in two flavors: Helidon SE and Helidon MP. Think about these flavors as frameworks providing similar functionality but offering different developer experiences.

Helidon SE Helidon MP

Gives you full transparency and puts you in control.

Built on top of the Helidon SE libraries and provides a platform that is familiar to enterprise Java developers.

Microframework model with a very small footprint and limited functionality (~7 MB).

MicroProfile implementation; slightly larger footprint than SE (~13 MB).

Functional style, reactive, non-blocking.

Declarative style with dependency injection.

Transparent "no magic" development experience; pure java application development with no annotations and no dependency injections.

Developer experience similar to that of Spring Boot, Jakarta EE and MicroProfile; layers on some Jakarta EE components (CDI, JAX-RS, JSON-P, JSON-B).

Learn more about Helidon SE.

Learn more about Helidon MP.

To help illustrate the differences, below are two samples implementing a simple RESTful service. One uses Helidon SE, the other Helidon MP.

Helidon SE sample
Routing routing = Routing.builder()
    .get("/hello",
        (req, res) -> res.send("Hello World"))
    .build();

WebServer.create(routing)
    .start();
Helidon MP sample
@Path("hello")
public class HelloWorld {
    @GET
    public String hello() {
        return "Hello World";
    }
}

What flavor shall I use?

Use Helidon SE if

  • Performance is your main goal.

  • You are familiar with reactive programming.

  • Your application is heavily using concurrency.

  • You are not planning to use any CDI-based components.

  • You want to use a minimum number of third-party dependencies.

Use Helidon MP if

  • You want to base your application on modern enterprise Java standards such as Jakarta EE and MicroProfile.

  • You are familiar with Java EE, Jakarta EE or Spring Boot and would like to have a similar development experience.

  • You are migrating existing Java EE/Jakarta EE application to microservices.

  • You are planning to use CDI components or extensions.

  • You are planning to use JPA for data access and Jersey (JAX-RS) for RESTful services.

Note

If you don’t know which Helidon flavor to use – use Helidon MP.

Prerequisites

Helidon requires Java and Maven. You might also need Docker and Kubernetes depending on how you plan to deploy your services.

Table 1. Prerequisite product versions for Helidon {helidon-version}

/../includes/prerequisites.adoc

We also strongly suggest installing the Helidon CLI (command line interface) which helps in generating and building Helidon projects.

Migration

In case you need to upgrade the version of Helidon, follow the Migration Guides.

For migration from Helidon 1.x to 2.x:

For migration from Helidon 2.x to 3.x:

Next Steps

Choose a Helidon flavor to explore and start using it. Check out the following: