bad.scala

case class SomeModel(field1: String, field2)

def js[A:Reads](field: String)(implicit request: Request[JsValue]): Option[A] = (request.body \ field).asOpt[A]

def index = Action(parse.json) { implicit request =>
  val field1 = js[String]("field1")
  val field2 = js[String]("field2")

  if(!field1.isDefined){
    BadRequest(Json.toJson(Map("error" -> "Field 'field1' is not defined")))
  } else if(!field2.isDefined){
    BadRequest(Json.toJson(Map("error" -> "Field 'field2' is not defined")))
  } else {
    val model = SomeModel(field1.get, field2.get) //Should be ok because of the if checks above
    // ...
    // ...
    Ok(Json.toJson(Map("message"->"everything was ok")))
  }
}