How to use @Reflective annotation to generate native hints?

Question

Trying to make classes generated by openapi-generator Spring Native capable so that they work in a native image.

The idea is to annotate all generated classes with @Reflective so that they are automatically generated in reflect-config.json. However, I can't seem to get through the @Reflective feature sufficiently and it doesn't work.

I've always done quite well with reflect-config.json in /resources/META-INF/native-image/, so my first idea was to get all the POJOs in there.

So I tried the following:

OpenApi Maven Generator configOption for the java generator:

<configOptions> 
  <additionalModelTypeAnnotations>@org.springframework.aot.hint.annotation.Reflective</additionalModelTypeAnnotations>
</configOptions> 

This creates valid annotations on all POJOs. Subsequently:

mvn clean compile spring-boot:process-aot package

and a few smoke tests with :

"C:/Program Files/GraalVM/graalvm-jdk-21/bin/java" \
-Dspring.aot.enabled=true \
-agentlib:native-image-agent=config-output-dir=C:/repos/my-repo/portal-applications/services/my-service/target/native \
-jar target/app.jar

After smoke testing my application, this generates the reflect-config.json into the folder specified. However none of the @Reflective annotated types are present.

Perhaps @Reflective annotations are picked up by mvn clean package -Pnative spring-boot:build-image, making explicit mentioning in reflect-config.json obsolete?

Answer 1

Okay I couldn't get it to work using @Reflective, but what works is this strategy.

1. Implement a new implementation for RuntimeHintsRegistrar.
2. Use a library like org.reflections to find all POJOs annotated:

val reflections = Reflections("define.your.package", Scanners.TypesAnnotated)

val reflectiveClasses = reflections.getTypesAnnotatedWith(Reflective::class.java)

3. Register all POJOs manually:

reflectiveClasses.forEach {
  hints.reflection().registerType(it, MemberCategory.INVOKE_DECLARED_CONSTRUCTORS, MemberCategory.INTROSPECT_PUBLIC_CONSTRUCTORS)
}

4. Add a file aot.factories under META-INF/spring and put this content:

org.springframework.aot.hint.RuntimeHintsRegistrar=\
    define.your.package.YourClassRuntimeHints

Now when running mvn clean compile spring-boot:process-aot package your POJOs are present in reflect-config.json.

For reference:

class YourClassRuntimeHints : RuntimeHintsRegistrar {

    override fun registerHints(hints: RuntimeHints, classLoader: ClassLoader?) {

      val reflections = Reflections("define.your.package", Scanners.TypesAnnotated)

      val reflectiveClasses = reflections.getTypesAnnotatedWith(Reflective::class.java)

      reflectiveClasses.forEach {
            hints.reflection().registerType(
                it,
                INVOKE_DECLARED_CONSTRUCTORS,
                INTROSPECT_PUBLIC_CONSTRUCTORS,
                INVOKE_PUBLIC_METHODS,
                INTROSPECT_PUBLIC_METHODS
            )
        }
    }
}

It is not necessary and probably cumbersome to use @Reflective for that, you can also create your own annotation.