groovy script. Convert object with map attribute to json

test.groovy

def testMapToJson() {
    def obj = new DictionaryRow()
    obj.id = 1L
    obj.values = [
            (new DictionaryField().setId(1)) : 1,
            (new DictionaryField().setId(2)) : 2] as Map

    println new JsonBuilder(obj).toPrettyString()
}

testMapToJson()
/*
{
    "created": null,
    "values": {
        "DictionaryField(id=1, name=null, created=null, lastUpdated=null, key=null)": 1,
        "DictionaryField(id=2, name=null, created=null, lastUpdated=null, key=null)": 2
    },
    "id": 1,
    "dictionary": null,
    "lastUpdated": null
}
*/