How to convert generic potentially nested map Map[String, Any] to case class using any library in Scala?

Question

I\'ve not had much joy with reflection, this answer using shapeless works for some cases (but seems to have many edge cases) Shapeless code to convert Map[String, Any] to ca

Answer 1

I've found a reasonably neat way to do it using Spray Json

First we define a way to get to a JsObject from a Map[String, Any]

def mapToJsObject(map: Map[String, Any]): JsObject =
  JsObject(fields = map.mapValues(anyToJsValue))

def anyToJsValue(any: Any): JsValue = any match {
  case n: Int => JsNumber(n)
  case n: Long => JsNumber(n)
  case n: Double => JsNumber(n)
  case s: String => JsString(s)
  case true => JsTrue
  case false => JsFalse
  case null | None => JsNull
  case list: List[_] => JsArray(list.map(anyToJsValue).toVector)
  case Some(any) => anyToJsValue(any)
  case map: Map[String, Any] => mapToJsObject(map)
}

Then we can just use convertTo provided we have the implicit JsonFormat in scope

case class Address(street: String, zip: Int)
case class Person(name: String, address: Address)

implicit val addressFormat = jsonFormat2(Address.apply)
implicit val personFormat = jsonFormat2(Person.apply)

"Convert Person example map to Person JsObject" in {
  JsonUtils.mapToJsObject(
    Map(
      "name" -> "Tom",
      "address" -> Map("street" -> "Jefferson st", "zip" -> 10000)
    )
  ).convertTo[Person] must_=== Person("Tom", Address("Jefferson st", 10000))
}

 CAVEATs

Spray json only has out of box jsonFormat up to 22 fields!

Can not handle any custom types, e.g. java.sql.Timestamp, since this isn't a JSON type.