Mapping a string to case classes using Scala play - scala

Question

Using the Scala play library I'm attempting to parse the string :
var str = "{\"payload\": \"[{\\\"test\\\":\\\"123\\\",\\\"tester\\\":\\\"456\\\"}," +
"{\\\"test1\\\":\\\"1234\\\",\\\"tester2\\\":\\\"4567\\\"}]\"}";
into a list of Payload classes using code below :
import play.api.libs.json._
object TestParse extends App {
case class Payload(test : String , tester : String)
object Payload {
implicit val jsonFormat: Format[Payload] = Json.format[Payload]
}
var str = "{\"payload\": \"[{\\\"test\\\":\\\"123\\\",\\\"tester\\\":\\\"456\\\"}," +
"{\\\"test1\\\":\\\"1234\\\",\\\"tester2\\\":\\\"4567\\\"}]\"}";
println((Json.parse(str) \ "payload").as[List[Payload]])
}
build.sbt :
name := "akka-streams"
version := "0.1"
scalaVersion := "2.12.8"
lazy val akkaVersion = "2.5.19"
lazy val scalaTestVersion = "3.0.5"
libraryDependencies ++= Seq(
"com.typesafe.akka" %% "akka-stream" % akkaVersion,
"com.typesafe.akka" %% "akka-stream-testkit" % akkaVersion,
"com.typesafe.akka" %% "akka-testkit" % akkaVersion,
"org.scalatest" %% "scalatest" % scalaTestVersion
)
// https://mvnrepository.com/artifact/com.typesafe.play/play-json
libraryDependencies += "com.typesafe.play" %% "play-json" % "2.10.0-RC6"
It fails with exception :
Exception in thread "main" play.api.libs.json.JsResultException: JsResultException(errors:List((,List(JsonValidationError(List("" is not an object),WrappedArray())))))
Is the case class structure incorrect ?
I've updated the code to :
import play.api.libs.json._
object TestParse extends App {
import TestParse.Payload.jsonFormat
object Payload {
implicit val jsonFormat: Format[RootInterface] = Json.format[RootInterface]
}
case class Payload (
test: Option[String],
tester: Option[String]
)
case class RootInterface (
payload: List[Payload]
)
val str = """{"payload": [{"test":"123","tester":"456"},{"test1":"1234","tester2":"4567"}]}"""
println(Json.parse(str).as[RootInterface])
}
which returns error :
No instance of play.api.libs.json.Format is available for scala.collection.immutable.List[TestParse.Payload] in the implicit scope (Hint: if declared in the same file, make sure it's declared before)
implicit val jsonFormat: Format[RootInterface] = Json.format[RootInterface]

Answer 1

This performs the task but there are cleaner solutions :
import akka.actor.ActorSystem
import akka.stream.scaladsl.{Flow, Sink, Source}
import org.scalatest.Assertions._
import spray.json.{JsObject, JsonParser}
import scala.concurrent.Await
import scala.concurrent.duration.DurationInt
object TestStream extends App {
implicit val actorSystem = ActorSystem()
val mapperFlow = Flow[JsObject].map(x => {
x.fields.get("payload").get.toString().replace("{", "")
.replace("}", "")
.replace("[", "")
.replace("]", "")
.replace("\"", "")
.replace("\\", "")
.split(":").map(m => m.split(","))
.toList
.flatten
.grouped(4)
.map(m => Test(m(1), m(3).toDouble))
.toList
})
val str = """{"payload": [{"test":"123","tester":"456"},{"test":"1234","tester":"4567"}]}"""
case class Test(test: String, tester: Double)
val graph = Source.repeat(JsonParser(str).asJsObject())
.take(3)
.via(mapperFlow)
.mapConcat(identity)
.runWith(Sink.seq)
val result = Await.result(graph, 3.seconds)
println(result)
assert(result.length == 6)
assert(result(0).test == "123")
assert(result(0).tester == 456 )
assert(result(1).test == "1234")
assert(result(1).tester == 4567 )
assert(result(2).test == "123")
assert(result(2).tester == 456 )
assert(result(3).test == "1234")
assert(result(3).tester == 4567 )
}
Alternative, ioiomatic Scala answers are welcome.