Sample Helidon SE project that includes multiple REST operations.
With JDK21
mvn package
java -jar target/application.jarBasic:
curl -X GET http://localhost:8080/simple-greet
Hello World!
JSON:
curl -X GET http://localhost:8080/greet
{"message":"Hello World!"}
curl -X GET http://localhost:8080/greet/Joe
{"message":"Hello Joe!"}
curl -X PUT -H "Content-Type: application/json" -d '{"greeting" : "Hola"}' http://localhost:8080/greet/greeting
curl -X GET http://localhost:8080/greet/Jose
{"message":"Hola Jose!"}
# Prometheus Format
curl -s -X GET http://localhost:8080/observe/metrics
# TYPE base:gc_g1_young_generation_count gauge
. . .
# JSON Format
curl -H 'Accept: application/json' -X GET http://localhost:8080/observe/metrics
{"base":...
. . .
This example shows the basics of using Helidon SE Health. It uses the set of built-in health checks that Helidon provides plus defines a custom health check.
Note the port number reported by the application.
Probe the health endpoints:
curl -X GET http://localhost:8080/observe/health
curl -X GET http://localhost:8080/observe/health/readyThe generation of native binaries requires an installation of GraalVM 22.1.0+.
You can build a native binary using Maven as follows:
mvn -Pnative-image install -DskipTests
The generation of the executable binary may take a few minutes to complete depending on
your hardware and operating system. When completed, the executable file will be available
under the target directory and be named after the artifact ID you have chosen during the
project generation phase.
Make sure you have GraalVM locally installed:
$GRAALVM_HOME/bin/native-image --version
Build the native image using the native image profile:
mvn package -Pnative-image
This uses the helidon-maven-plugin to perform the native compilation using your installed copy of GraalVM. It might take a while to complete. Once it completes start the application using the native executable (no JVM!):
./target/application
Yep, it starts fast. You can exercise the application’s endpoints as before.
docker build -t application .
docker run --rm -p 8080:8080 application:latest
Exercise the application as described above.
If you don’t have access to a Kubernetes cluster, you can install one on your desktop.
kubectl cluster-info # Verify which cluster
kubectl get pods # Verify connectivity to cluster
kubectl create -f app.yaml # Deploy application
kubectl get pods # Wait for quickstart pod to be RUNNING
kubectl get service application # Get service info
kubectl port-forward service/application 8081:8080 # Forward service port to 8081
You can now exercise the application as you did before but use the port number 8081.
After you’re done, cleanup.
kubectl delete -f app.yaml
Build the custom runtime image using the jlink image profile:
mvn package -Pjlink-image
This uses the helidon-maven-plugin to perform the custom image generation. After the build completes it will report some statistics about the build including the reduction in image size.
The target/application-jri directory is a self contained custom image of your application. It contains your application, its runtime dependencies and the JDK modules it depends on. You can start your application using the provide start script:
./target/application-jri/bin/start
Class Data Sharing (CDS) Archive Also included in the custom image is a Class Data Sharing (CDS) archive that improves your application’s startup performance and in-memory footprint. You can learn more about Class Data Sharing in the JDK documentation.
The CDS archive increases your image size to get these performance optimizations. It can be of significant size (tens of MB). The size of the CDS archive is reported at the end of the build output.
If you’d rather have a smaller image size (with a slightly increased startup time) you can skip the creation of the CDS archive by executing your build like this:
mvn package -Pjlink-image -Djlink.image.addClassDataSharingArchive=false
For more information on available configuration options see the helidon-maven-plugin documentation.