Injecting Any Bean

If you are not particular about which bean gets injected then you can use the @Any qualifier which will inject the first available bean, for example:

Injecting Any Instance

    @Inject @Any
    Engine engine;

Injecting Any Instance

    @Inject @Any
    Engine engine

Injecting Any Instance

    @Inject
    @field:Any
    lateinit var engine: Engine

The @Any qualifier is typically used in conjunction with the BeanProvider interface to allow more dynamic use cases. For example the following Vehicle implementation will start the Engine if the bean is present:

Using BeanProvider with Any

import io.micronaut.context.BeanProvider;
import io.micronaut.context.annotation.Any;
import jakarta.inject.Singleton;
@Singleton
public class Vehicle {
    final BeanProvider<Engine> engineProvider;
    public Vehicle(@Any BeanProvider<Engine> engineProvider) { (1)
        this.engineProvider = engineProvider;
    }
    void start() {
        engineProvider.ifPresent(Engine::start); (2)
    }
}

Using BeanProvider with Any

import io.micronaut.context.BeanProvider
import io.micronaut.context.annotation.Any
import jakarta.inject.Singleton
@Singleton
class Vehicle {
    final BeanProvider<Engine> engineProvider
    Vehicle(@Any BeanProvider<Engine> engineProvider) { (1)
        this.engineProvider = engineProvider
    }
    void start() {
        engineProvider.ifPresent(Engine::start) (2)
    }
}

Using BeanProvider with Any

import io.micronaut.context.BeanProvider
import io.micronaut.context.annotation.Any
import jakarta.inject.Singleton
@Singleton
class Vehicle(@param:Any val engineProvider: BeanProvider<Engine>) { (1)
    fun start() {
        engineProvider.ifPresent { it.start() } (2)
    }
    fun startAll() {
        if (engineProvider.isPresent) { (1)
            engineProvider.forEach { it.start() } (2)
        }
}

If there are multiple beans you can also adapt the behaviour. The following example starts all the engines installed in the Vehicle if any are present:

Using BeanProvider with Any

    void startAll() {
        if (engineProvider.isPresent()) { (1)
            engineProvider.stream().forEach(Engine::start); (2)
        }
    }

Using BeanProvider with Any

    void startAll() {
        if (engineProvider.isPresent()) { (1)
            engineProvider.each {it.start() } (2)
        }
    }

Using BeanProvider with Any

    fun startAll() {
        if (engineProvider.isPresent) { (1)
            engineProvider.forEach { it.start() } (2)
        }