Helidon

Status: Production-ready, Active

Java Version: 21+

Learning Curve: Moderate

Last Release: v4.1.6 (2026)

Helidon is Oracle's collection of lightweight Java libraries for building cloud-native microservices, designed around Java virtual threads (Project Loom). It's the world's first web server written entirely on virtual threads, providing exceptional throughput and scalability. Helidon offers two programming models: Helidon MP (MicroProfile) with familiar JAX-RS, CDI, and JSON-P/B APIs, and Helidon SE with a modern functional/reactive approach. The framework includes comprehensive observability with health checks, metrics, telemetry (OpenTelemetry), and fault tolerance integrations with Prometheus, Jaeger, and Zipkin. GraalVM Native Image support allows compilation to small-footprint native executables, while persistence support covers JDBC drivers and both relational and non-relational databases. Helidon is ideal for enterprise teams building cloud-ready microservices that need MicroProfile compatibility combined with cutting-edge virtual thread performance.

Code Example

import io.helidon.webserver.WebServer;
            import io.helidon.webserver.http.HttpRouting;
            
            public class HelloHelidon {
                public static void main(String[] args) {
                    HttpRouting routing = HttpRouting.builder()
                        .get("/hello", (req, res) -> {
                            res.send("Hello, Helidon!");
                        })
                        .get("/greet/{name}", (req, res) -> {
                            String name = req.path().pathParameters().get("name");
                            res.send("Hello, " + name + "!");
                        })
                        .build();
            
                    WebServer server = WebServer.builder()
                        .routing(routing)
                        .port(8080)
                        .build()
                        .start();
                    
                    System.out.println("Server started at: http://localhost:8080");
                }
            }