How to convert a map to json where one of the types is AnyRef

I have a Map which is of the type [String, AnyRef]. How do i convert it to Json using play-json. I found some answers but they all had a type defined. When i tried converting i got the compiler error message as:

> No implicit arguments of type: Writes[Map[String, AnyRef]]

val testMap: Map[String, AnyRef] = Map.empty[String, AnyRef]

Suppose this map has the following data:

{ "lastModifiedTime" -> 1575311400000,
    "user_id" -> 1,
    "user_email" -> "user@email.com",
    "is_active" -> true,
    "project_id" -> 1,
    "status"-> "COMPLETED" }

So my question is if I have AnyRef as the second type in map how will I convert it to Json using just play-Json ?

Correction => <br/>
This map is obtained as a result of elastic search result, so i cannot guarantee that every time the map will be same, but it will be of the same type that is, Map[String, AnyRef].

Play-json try to be as typesafe as possible and this means it cannot provide implicitly serializer for Map[String, AnyRef]. It could shadow other serializers and it couldn't ensure it will not fail. You can create your own but it'll be hard-coded and you should not put it in your globals:

// Start writing your ScalaFiddle code here
import play.api.libs.json._

val testMap = Map[String,Any](
  "test" -> 1, 
  "otherTest" -> "denada",
  "mapsAlsoWorksSomehow" -> Map (
    "wee" -> true,
    "mapsEverywhere" -> Map (
       "wee" -> false, "prr" -> new java.util.Date(),
    ),
    "ops" -> new java.lang.Integer(22) 
  )
)

//you can create your own function that just maps objects to JsValues without using types...
//not safe but works
def toJsValue(a:Any):JsValue = a match {
  case v:JsValue => v
  case v:Map[String,_] => JsObject(v.map { case (k,v) => (k, toJsValue(v)) }) //keep in mind we assume this is map of [String,Any] if not it will blow up :(
  case v:String => JsString(v)
  case v:Int => JsNumber(v)
  case v:Boolean => JsBoolean(v)
  case v:java.util.Date => JsString(v.toString)
  case v if v == null => JsNull
}

implicit lazy val anyWriter:Writes[Map[String,Any]] = new Writes[Map[String,Any]] {
  def writes(a:Map[String,Any]):JsValue = toJsValue(a)
}


println(Json.toJson(testMap))
println(toJsValue(testMap))

//here we use anyWriter implicitly but there is other one... currently shadowed :(.
println(Json.toJson(testMap.mapValues[JsValue] { case (v) => toJsValue(v) }))

But keep in mind that it will blow up when You will have unsupported type in Map. I guess best way is not to create implicit writer but use toJsValue method on arguments of a map and then try to serialize it (like in last println).

demo

If it was helpful, up-vote please and mark as answer.

The simplest option is to convert all the values to String and save that.

val stringMap = testMap.mapValues(_.toString)

Failing that you either have to create a custom handler for AnyRef or manually create a JObject from the Map and use match to select the specific JSON type for each element.

You cannot do that.

The closest thing to AnyRef you can have is play.api.libs.json.JsValue.

Or in other words you need a JSON-like object structure, where you have Writers, resp. Readers.

Let me know if you need further explanation.