Myujth

i've extracted a map from json. This works so far. As I don't know before parsing which fields are there in the json, I've been using a Map[String, Any]. Every field only consisting of digits is interpreted as a BigInt, which I don't want.

MyCode:

 implicit val formats: DefaultFormats.type = org.json4s.DefaultFormats
 json.extract[Map[String, Any]]

Any way to implicitly make the numbers interpreted as Int or Long?

You did not specify, how the json value is created. If you parse it from a String, than the useBigIntForLong flag does the trick:

import org.json4s.DefaultFormats
import org.json4s.JsonAST._
import org.json4s.native.JsonMethods

object Main 

 def main(args: Array[String]): Unit = 
 implicit val formats: DefaultFormats = DefaultFormats

 val parsedJson = JsonMethods.parse(""" "a" : 42 """, useBigIntForLong = false)
 parsedJson.extract[Map[String, Any]].foreach 
 case (name, value) => println(s"$name = $value ($value.getClass)")
 
 

Output:

a = 42 (class java.lang.Long)

If you construct the json value programmatically, than you choose between BigInt and Long directly:

val constructedJson = JObject(
 "alwaysBigInt" -> JInt(42),
 "alwaysLong" -> JLong(55),
)
constructedJson.extract[Map[String, Any]].foreach 
 case (name, value) => println(s"$name = $value ($value.getClass)")

Output:

alwaysBigInt = 42 (class scala.math.BigInt)
alwaysLong = 55 (class java.lang.Long)

Example source code