How to extract List and Map in json4s

Question

I'm new in Scala and do not know how to deal with this Json with json4s:

After parsing the json and extracting the following json through:

val data = json \\ "someKey"

I have a Json like this:

[{"Id":14706061,
   "Rcvr":1,
    "HasSig":true,
    "Sig":80},
 {"Id":3425490,
  "Rcvr":1,
  "HasSig":false,
  "Sig": 80}]

Printing it to the console, it returns:

JArray(List(JObject(List((Id,JInt(14706061)), (Rcvr,JInt(1)), (HasSig,JBool(true)), (Sig,JInt(80), Id,JInt(3425490)), (Rcvr,JInt(1)), (HasSig,JBool(false)), (Sig,JInt(80) ))

So, after that I used:

println("show values: " + data.values)

And had:

List(Map(Id -> 14706061, Rcvr -> 1, HasSig -> true, Sig -> 80), Map(Id -> 3425490, Rcvr -> 1, HasSig -> false, Sig -> 80))

But I don't know how to extract each Map from each position of the List.

I also tried to extract to a case class but I had 0 entries:

case class Example (Id: BigInt, Rcvr: Int, HasSig: Boolean, Sig: Int)

case class ExampleList (examples: List[Example])

implicit val formats = DefaultFormats.strict

val dataList = data.extract[ExampleList]

Thanks in advance for your help

PD. If I assign:

val dataList = data.values

The type of dataList (with getClass) is: class scala.collection.immutable.$colon$colon

PD2. SOLUTION

After the:

 val data = json \\ "someKey"

I put:

val dataList = data.extract[JArray] val examples = dataList.values

It returns an iterable Array with its Maps iterable, so fixed.

Checked with:

println("number of elements: " + examples.length)

and

println("show each item: " + examples.foreach(println))

Thanks for taking your time in reading.

Answer 1

If you want to extract into a Case Class instead of a Map, the correct type for extraction is List[Example], instead of ExampleList.

ExampleList has an attribute examples, your json doesn't. That is why you got an empty list.

import org.json4s.native.JsonMethods._
import org.json4s._

implicit val formats = DefaultFormats

val str = """[{"Id":14706061,
             "Rcvr":1,
              "HasSig":true,
              "Sig":80},
           {"Id":3425490,
            "Rcvr":1,
            "HasSig":false,
            "Sig": 80}]"""


case class Example (Id: BigInt, Rcvr: Int, HasSig: Boolean, Sig: Int)

val json = parse(str)

val examples = json.extract[List[Example]]