#json #Reads 2 fields that must be present exclusively #XOR #play2.1

CODE.scala

import play.api.libs.json._
import play.api.libs.functional.syntax._
 
val r = (
  (__ \ "field1").readNullable[String] and
  (__ \ "field2").readNullable[Int]
).tupled.filter(ValidationError("unexpected result")){
  case( Some(x), None ) => true;
  case ( None, Some(x) ) => true;
  case _ => false
}

Test.scala

scala> Json.obj("field1" -> "toto").validate(r)
res19: play.api.libs.json.JsResult[(Option[String], Option[Int])] = JsSuccess((Some(toto),None),)

scala> Json.obj("field2" -> 5).validate(r)
res20: play.api.libs.json.JsResult[(Option[String], Option[Int])] = JsSuccess((None,Some(5)),)

scala> Json.obj("field2" -> "toto").validate(r)
res21: play.api.libs.json.JsResult[(Option[String], Option[Int])] = JsError(List((/field2,List(ValidationError(validate.error.expected.jsnumber,WrappedArray())))))

scala> Json.obj("field1" -> "toto", "field2" -> 5).validate(r)
res22: play.api.libs.json.JsResult[(Option[String], Option[Int])] = JsError(List((,List(ValidationError(unexpected result,WrappedArray())))))

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