Play [Scala]: How to flatten a JSON object

Question

Given the following JSON...

{
  \"metadata\": {
    \"id\": \"1234\",
    \"type\": \"file\",
    \"length\": 395
  }
}

... how do I convert it

Answer 1

Thanks m-z, it is very helpful. (I'm not so familiar with Scala.)

I'd like to add a line for "flatten" working with primitive JSON array like "{metadata: ["aaa", "bob"]}".

  def flatten(js: JsValue, prefix: String = ""): Seq[JsValue] = {

    // JSON primitive array can't convert to JsObject
    if(!js.isInstanceOf[JsObject]) return Seq(Json.obj(prefix -> js))

    js.as[JsObject].fieldSet.toSeq.flatMap{ case (key, values) =>
      values match {
        case JsBoolean(x) => Seq(Json.obj(concat(prefix, key) -> x))
        case JsNumber(x) => Seq(Json.obj(concat(prefix, key) -> x))
        case JsString(x) => Seq(Json.obj(concat(prefix, key) -> x))
        case JsArray(seq) => seq.zipWithIndex.flatMap{ case (x, i) => flatten(x, concat(prefix, key + s"[$i]")) }
        case x: JsObject => flatten(x, concat(prefix, key))
        case _ => Seq(Json.obj(concat(prefix, key) -> JsNull))
      }
    }
  }