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

Here's my take on this problem, based on @Travis Brown's 2nd solution.

It recursively traverses the json and prefixes each key with its parent's key.

def flatten(js: JsValue, prefix: String = ""): JsObject = js.as[JsObject].fields.foldLeft(Json.obj()) {
    case (acc, (k, v: JsObject)) => {
        if(prefix.isEmpty) acc.deepMerge(flatten(v, k))
        else acc.deepMerge(flatten(v, s"$prefix.$k"))
    }
    case (acc, (k, v)) => {
        if(prefix.isEmpty) acc + (k -> v)
        else acc + (s"$prefix.$k" -> v)
    }
}

which turns this:

{
  "metadata": {
    "id": "1234",
    "type": "file",
    "length": 395
  },
  "foo": "bar",
  "person": {
    "first": "peter",
    "last": "smith",
    "address": {
      "city": "Ottawa",
      "country": "Canada"
    }
  }
}

into this:

{
  "metadata.id": "1234",
  "metadata.type": "file",
  "metadata.length": 395,
  "foo": "bar",
  "person.first": "peter",
  "person.last": "smith",
  "person.address.city": "Ottawa",
  "person.address.country": "Canada"
}