How to create a singleton for each bean definition

[KDanisme]

Hi,
Is have a custom annotation which is also annotated with @Prototype

...
@Prototype
annotation class Aggregate(
...

I need to create a Singleton for each class annotated with @Aggregate

I don't see how I can do this gradefully.

If only @EeachBean worked on annotations or something that would solve my issue i guess.

Am I missing something?

[TatyOko28]

Solution : Use @factory with @EachBean (Recommended)

Create a factory that finds all classes with @Aggregate and produces a singleton for each.

import io.micronaut.context.annotation.Bean
import io.micronaut.context.annotation.EachBean
import io.micronaut.context.annotation.Factory
import io.micronaut.core.annotation.AnnotationMetadata
import io.micronaut.inject.BeanDefinition
import io.micronaut.inject.qualifiers.Qualifiers
import jakarta.inject.Singleton

@Factory
class AggregateBeanFactory(
    private val beanDefinitions: List<BeanDefinition<*>>
) {
    
    @EachBean(AggregateClassHolder::class)
    fun aggregateService(holder: AggregateClassHolder): AggregateService {
        // Create a singleton for each @Aggregate-annotated class
        return AggregateServiceImpl(holder.aggregateClass)
    }
}

// Holder class for EachBean (required because @EachBean works on a bean, not directly on types)
@Singleton
class AggregateClassHolder(
    val aggregateClass: Class<*>,
    val annotation: Aggregate
)

// Producer that creates a holder for each @Aggregate-annotated class
@Factory
class AggregateClassScanner(
    val beanDefinitions: List<BeanDefinition<*>>
) {
    
    @Bean
    fun aggregateClassHolders(): List<AggregateClassHolder> {
        return beanDefinitions
            .filter { it.hasAnnotation(Aggregate::class.java) }
            .mapNotNull { beanDef ->
                val annotation = beanDef.getAnnotation(Aggregate::class.java)
                if (annotation != null) {
                    AggregateClassHolder(beanDef.beanType, annotation)
                } else null
            }
    }
}