For this purpose, the annotation allows you to bind a map to a single configuration property, and specify whether to accept a flat map of keys to values, or a nested map (where the values may be additional maps].

@MapFormat Example

@MapFormat Example

import javax.validation.constraints.Min
import io.micronaut.core.convert.format.MapFormat
@ConfigurationProperties('my.engine')
class EngineConfig {
    @Min(1L)
    int cylinders
    @MapFormat(transformation = MapFormat.MapTransformation.FLAT) (1)
    Map<Integer, String> sensors
}

import io.micronaut.context.annotation.ConfigurationProperties
import javax.validation.constraints.Min
import io.micronaut.core.convert.format.MapFormat
@ConfigurationProperties("my.engine")
class EngineConfig {
    @Min(1L)
    var cylinders: Int = 0
    var sensors: Map<Int, String>? = null

EngineImpl

EngineImpl

@Singleton
class EngineImpl implements Engine {
    @Inject EngineConfig config
    @Override
    Map getSensors() {
        config.sensors
    }
    String start() {
        "Engine Starting V${config.cylinders} [sensors=${sensors.size()}]"
    }
}

EngineImpl

@Singleton
class EngineImpl : Engine {
    override val sensors: Map<*, *>?
        get() = config!!.sensors
    @Inject
    var config: EngineConfig? = null
    override fun start(): String {
        return "Engine Starting V${config!!.cylinders} [sensors=${sensors!!.size}]"
    }
}

Use Map Configuration

Use Map Configuration

        ApplicationContext applicationContext = ApplicationContext.run(
                ['my.engine.cylinders': '8', 'my.engine.sensors': [0: 'thermostat', 1: 'fuel pressure']],
                "test"
        )
        Vehicle vehicle = applicationContext
                .getBean(Vehicle)
        println(vehicle.start())

Use Map Configuration

        val subMap = mapOf(
                0 to "thermostat",
                1 to "fuel pressure"
        )
        val map = mapOf(
                "my.engine.cylinders" to "8",
                "my.engine.sensors" to subMap
        )
        val applicationContext = ApplicationContext.run(map, "test")
        val vehicle = applicationContext.getBean(Vehicle::class.java)