Introduction

Helidon SE is Helidon’s foundational set of APIs and, as of Helidon 4, it uses virtual threads to enable these APIs to change from asynchronous to blocking.

Components

The REST framework for Helidon SE is the Helidon WebServer. It was built from the ground up to take full advantage of Java 21’s virtual threads.

Helidon SE supports a number of additional Helidon features:

Name	Description
Config	A flexible configuration framework with support for multiple sources and formats.
CORS	Add support for CORS to your application using a Helidon module.
DB Client	Provides a unified, reactive API for working with databases in non-blocking way.
GraphQL	Build GraphQL servers.
gRPC	Build gRPC servers and clients.
Health Checks	Expose health statuses of your applications.
Injection	Use of the Helidon injection in your applications.
JSON Schema	Creation of the JSON Schema in your applications.
Metrics	Instrumentation to expose metrics of your applications.
OpenAPI	Support OpenAPI from your application.
Reactive Messaging	Use prepared tools for repetitive use case scenarios.
Reactive Streams	APIs to work with reactive streams in Helidon.
Security	A tool-chain to handle authentication, authorization and context propagation.
Tracing	Profile and monitor your applications across multiple services.
WebClient	HTTP client that handles responses to the HTTP requests.
WebServer	A programmatic HTTP API that uses virtual threads to handle nearly unlimited concurrent requests without blocking a platform thread or starving other requests.
WebSocket	Enables Java applications to participate in WebSocket interactions as both servers and clients.

Upgrade

In case you need to upgrade the version of Helidon, follow the upgrade guides:

Name	Description
Helidon SE 4x Upgrade Guide	Follow this guide to migrate your application from Helidon 3.x to 4.x.
Helidon SE 3x Upgrade Guide	Follow this guide to migrate your application from Helidon 2.x to 3.x.
Helidon SE 2.x Upgrade Guide	Follow this guide to migrate your application from Helidon 1.x to 2.x.

Next Steps

Try the Helidon SE quickstart guides to get your first Helidon SE application up and running in minutes.

Name	Description
Guides	Follow step-by-step guides to build your applications using Helidon SE.
Javadocs	Browse the Helidon Javadocs.