How to use different names when mapping JSON array to Scala object using combinators - json

Question

Given a JSON array like this one:
{
"success": true,
"data": [
{
"id": 600,
"title": "test deal",
"e54cbe3a434d8e6": 54
},
{
"id": 600,
"title": "test deal",
"e54cbe3a434d8e6": 54
},
],
"additional_data": {
"pagination": {
"start": 0,
"limit": 100,
"more_items_in_collection": false
}
}
}
In my Play 2.2.2 application, using the Scala JSON Reads Combinator, everything works going this way:
implicit val entityReader = Json.reads[Entity]
val futureJson: Future[List[Entity]] = futureResponse.map(
response => (response.json \ "data").validate[List[Entity]].get
The problem now is the key named 'e54cbe3a434d8e6' which I would like to name 'value' in my object:
// This doesn't work, as one might expect
case class Entity(id: Long, title: String, e54cbe3a434d8e6: Long)
// I would like to use 'value' instead of 'e54cbe3a434d8e6'
case class Entity(id: Long, title: String, value: Long)
There is vast information about the combinators here and here but I only want to use a fieldname which is different from the key name in the JSON array. Can some one help me to find a simple way?
I suppose it has got something to do with JSON.writes?!

Answer 1

One simple way without trying to apply transformations on json itself is to define a custom Reads in such a way to handle this:
val json = obj(
"data" -> obj(
"id" -> 600,
"title" -> "test deal",
"e54cbe3a434d8e6" -> 54))
case class Data(id: Long, title: String, value: Int)
val reads = (
(__ \ "id").read[Long] ~
(__ \ "title").read[String] ~
(__ \ "e54cbe3a434d8e6").read[Int] // here you get mapping from your json to Scala case class
)(Data)
def index = Action {
val res = (json \ "data").validate(reads)
println(res) // prints "JsSuccess(Data(600,test deal,54),)"
Ok(json)
}
Another way is to use combinators like this:
... the same json and case class
implicit val generatedReads = reads[Data]
def index = Action {
val res = (json \ "data").validate(
// here we pick value at 'e54cbe3a434d8e6' and put into brand new 'value' branch
__.json.update((__ \ "value").json.copyFrom((__ \ "e54cbe3a434d8e6").json.pick)) andThen
// here we remove 'e54cbe3a434d8e6' branch
(__ \ "e54cbe3a434d8e6").json.prune andThen
// here we validate result with generated reads for our case class
generatedReads)
println(res) // prints "JsSuccess(Data(600,test deal,54),/e54cbe3a434d8e6/e54cbe3a434d8e6)"
Ok(prettyPrint(json))
}