https://ratpack.slack.com/archives/ratpack/p1458835847000315

ratpackConfig.groovy

class MyConfig {
    private final String dogsName
    private final int dogsAge
    private final List<Raindeer> raindeers

    static class Raindeer {
        private final String name
        private final String position

        @JsonCreator
        Raindeer(@JsonProperty('name') String name,
                 @JsonProperty('position') String position) {
            this.name = name
            this.position = position
        }
    }

    @JsonCreator
    public MyConfig(@JsonProperty('dogsName') String dogsName,
                    @JsonProperty('dogsAge') int dogsAge,
                    @JsonProperty('raindeers') Map<String,Raindeer> s) {
        this.dogsName = dogsName
        this.dogsAge = dogsAge
        this.raindeers = s.values().toList()
    }
}

//MYC_APP__DOGS_NAME=woofer2 MYC_APP__DOGS_AGE=31 MYC_APP__RAINDEERS__1__NAME=Rudolf MYC_APP__RAINDEERS__1__POSITION=Front MYC_APP__RAINDEERS__2__NAME=Comet MYC_APP__RAINDEERS__2__POSITION=Back groovy rpcdemo.groovy