Native Micronaut 👩‍🚀

Getting Started

Go to micronaut.io/launch and generate your project. You might want to pay attention to defaults — I chose latest Java, Maven, and JUnit. For the sake of this project, our demo will be called library.

For now we are not adding any dependencies — support for GraalVM Native Image is already implicitly included out of the box.

Build and run the app on the JVM:

mvn mn:run

Build and run the app as a native image:

mvn package -Dpackaging=native-image
./target/library

The Application

Now let's design our application. It will be a home library application, containing books and exposing several endpoints to retrieve them. For that, we added Library and Book classes, and a Controller, Service, and Repository to work with the data and interact with the user.

Reflection

For cases where you have custom reflection code, and Native Image isn't able to resolve it auotmatically, the best solution is to use programmatic reflection configuration. In Micronaut, use the @ReflectConfig annotation. For example:

package example.micronaut;

import io.micronaut.core.annotation.ReflectionConfig;

@ReflectionConfig(
        type = StringReverser.class,
        methods = {
                @ReflectionConfig.ReflectiveMethodConfig(name = "reverse", parameterTypes = {String.class})
        }
)

public class NativeImageConfig {
}

The syntax for working with the agent:

java -agentlib:native-image-agent -jar ./target/demo.jar