How do I update a nested key of a JsObject in scala - json

Question

In my code I make a get request to a server to get some json, and then I want to update one of the values before I send it back. I know that if the key was on the top level I could just update the key by writing
val newConfig = originalConfig ++ Json.obj("key" -> newValue)
however I cannot figure out a nice way to update it if the key I want to change is a couple of layers in.
ie. My json looks like this, and I want to just update key5
{
"key1": "value",
"key2": {
"key3": "value",
"key4": {
"key5": "value",
"key6": "value"
}
}
}
Is there a way to do this without updating it layer by layer?
ie.
val key4 = originalKey4 ++ Json.obj("key5" -> newValue)
val key2 = originalKey2 ++ Json.obj("key4" -> key4)
val newJson = originalJson ++ Json.obj("key2" -> key2)
The actual key that I want to update is 7 layers in, so this is rather tedious.

Answer 1

Take look at json transformers
import play.api.libs.json._
val str = """{
| "key1": "value",
| "key2": {
| "key3": "value",
| "key4": {
| "key5": "value",
| "key6": "value"
| }
| }
|}""".stripMargin
val json = Json.parse(str)
val transformer = (__ \ 'key2 \ 'key4 \ 'key5).json.update(
__.read[JsString].map(_ => Json.toJson("updated value"))
)
val result = json.transform(transformer).asOpt.get
Json.prettyPrint(result)
res0: String = {
"key1" : "value",
"key2" : {
"key3" : "value",
"key4" : {
"key5" : "updated value",
"key6" : "value"
}
}
}