Json body converted to sealed trait

Question

I have a Play! endpoint which can receive a json body as 3 or 4 forms (I tried using generic type, but not working).

Controller:

def getChartData = Action.async(parse.json) { request =>
   // ERROR: can not cast JsValue to type ChartDataRequest (which is sealed trait)
   service.getChartData(request.body.asInstanceOf[ChartDataRequest]).map {
     data => Ok(Json.toJson(data))
   }.recover { 
     case _ => InternalServerErrror
   }
}

Service:

def getChartData(request: ChartDataRequest): Future[data_type] = {
  if (request.isInstanceOf[PieChartRequest]) {
    //
  } else if (request.isInstanceOf[BarChartRequest]) {
    //
  } else {
    //
  }
}

dtos:

sealed trait ChartDataRequest

final case class PieChartRequest(field1: String, field2: String, ....) 
   extends ChartDataRequest

final case class BarChartRequest(field1: String, field2: String, ....) 
   extends ChartDataRequest

I found here the solution to use sealed traits, but can't do it well.

In this point, I can not convert the JsValue to ChartDataRequest type. I can use a field "classType" in my json and then using the match pattern to create the specified object (PieDataRequest or BarDataRequest) but I think this is not the best solution.

Inside all my controller methods where I send objects as json body, I use the play validator, but have the same problem, and I removed it from code.

// ChartDataRequest can have PieDataRequest or BarDataRequest type
request.body.validate[ChartDataRequest] match {
    case JsSuccess(value, _) => // call the service
    case JsError(_) => Future(BadRequest("Invalid json body"))
 }

thanks

Seems like you have it all working, what is exactly your question? — Tomer Shetah, Feb 22 '21 at 13:56
I get error at `request.body.asInstanceOf[ChartDataRequest]`. info: `Exhaustive checking allows to check that all members of a sealed trait must be declared in the same file as of the source file`. I declared sealed trait below case classes, maybe this is one of the problems. I solved it using a general case class with fields : `classType` (which can be "pie", "bar", "anything") and a field `value` (JsValue). Then, matching `classType` with cases and parsing json as `[T]`. — AlleXyS, Feb 22 '21 at 14:09
Looks like you are not pattern matching all options, what is the code that procudes this error? — Tomer Shetah, Feb 22 '21 at 14:10

John · Accepted Answer · 2021-02-22T20:05:37.920

You can follow this:

        sealed trait ChartDataRequest

  final case class PieChartRequest(field1: String) extends ChartDataRequest

  final case class BarChartRequest(field2: String) extends ChartDataRequest

  final case object WrongData extends ChartDataRequest

  import play.api.libs.json._
  import play.api.libs.functional.syntax._

  implicit val ChartDataRequests: Reads[ChartDataRequest] = {
    val pc = Json.reads[PieChartRequest]
    val bc = Json.reads[BarChartRequest]
    __.read[PieChartRequest](pc).map(x => x: ChartDataRequest) |
      __.read[BarChartRequest](bc).map(x => x: ChartDataRequest)

  }


  def getChartData(request: ChartDataRequest) = {

    request match {
      case _: PieChartRequest =>
        Future("PieChartRequest")(defaultExecutionContext)
      case _: BarChartRequest =>
        Future("BarChartRequest")(defaultExecutionContext)
      case _ =>
        Future("WrongData")(defaultExecutionContext)
    }
  }

  def getChartDataAction = Action.async(parse.json) { request =>
    // you can separate this to a new function
    val doIt = request.body.asOpt[JsObject].fold[ChartDataRequest](
      WrongData
    ){
      jsObj =>
        jsObj.asOpt[ChartDataRequest].fold[ChartDataRequest](
         WrongData
        )(identity)
    }

    getChartData(doIt).map {
      data => Ok(Json.toJson(data))
    }(defaultExecutionContext).recover {
      case _ => InternalServerError
    }(defaultExecutionContext)
  }

Json body converted to sealed trait

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