Traversing multiple JSON arrays in Play/Scala

Question

{
    "location":{
        "residents":[{
            "renting":[{
                "name":"John Doe"
                "pets":"2"
            },{
                "name":"Jane Smith"
                "pets":"2"
            }]
        }]
    }
}

I can successfully traverse location with this -

val json = ...

val rentReads = (__ \ 'location).read[String]

val rentResult = json.validate[String](rentReads)

rentResult match {
  case s: JsSuccess[String] => Ok(s.get)
  case e: JsError => Ok("Errors: " + JsError.toFlatJson(e).toString())
}

Based on the documentation, I should be able to do something like this -

val skillReads = ((__ \ 'location) \ 'residents)(0).read[String]

but it results in the following error -

Errors: {"obj.VariationResultsWrapper.VariationResultSets[0]":[{"msg":"error.path.missing","args":[]}]}

At this point I'm just trying to understand how to return values from "renting" only. Eventually, I would like to map that result to a case class.

Ryan · Accepted Answer · 2015-03-15 07:24:21Z

2

If your eventual goal is to parse this into case classes, just define those case classes and let Play do the heavy lifting.

case class Renting(name: String, pets: String)
case class Resident(renting: List[Renting])
case class Location(residents: List[Resident])

implicit val rentingFormat = Json.format[Renting]
implicit val residentFormat = Json.format[Resident]
implicit val locationFormat = Json.format[Location]

(json \ "location").validate[Location]
res1: play.api.libs.json.JsResult[Location] = JsSuccess(Location(List(Resident(List(Renting(John Doe,2), Renting(Jane Smith,2))))),/residents)

answered Mar 15, 2015 at 7:24

Ryan

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