How to convert json4s JValue to Jackson JsonNode?

Question

If I am working with json4s (using Jackson bindings):

scala> import org.json4s._
scala> import org.json4s.jackson.JsonMethods._
scala> parse(""" { "numbers" : [1, 2, 3, 4] } """)
res0: org.json4s.JsonAST.JValue =
      JObject(List((numbers,JArray(List(JInt(1), JInt(2), JInt(3), JInt(4))))))

How can I convert a given org.json4s.JsonAST.JValue like the above to a com.fasterxml.jackson.databind.JsonNode?

For why I want to do this: I want to validate JValues against JSON Schemas, using the excellent json-schema-validator Java library, which takes JsonNodes as arguments.

I am looking for some kind of equivalent to the Play Framework's handling of JsValue <> JsonNode interop.

Answer 1

Since Json4s 3.2.11-SNAPSHOT there are two methods which can convert between JValue and JsonNode:

• asJsonNode(jv: JValue): JsonNode converts a JValue to a JsonNode
• fromJsonNode(jn: JsonNode): JValue converts a JsonNode to a JValue

Here is an example how to use it:

import org.json4s._
import org.json4s.jackson.JsonMethods._

val jv = parse(""" { "numbers" : [1, 2, 3, 4] } """)

val jn = asJsonNode(jv)
println(jn)
// {"numbers":[1,2,3,4]}

val jv2 = fromJsonNode(jn)
println(jv2)
// JObject(List((numbers,JArray(List(JInt(1), JInt(2), JInt(3), JInt(4))))))