Json4s add JValue to JArray

Question

I'm using scala and Json4s to add a JValue to a JArray in a loop, this way:

    var recordsJArray = JArray
    for (record <- recordsList) {
       val mrecord= new com.google.gson.Gson().toJson(record.asMap())
       val jsonRecord = parse(mrecord)
       recordsJArray = recordsJArray.++jsonRecord
    }

I've searched de api: https://static.javadoc.io/org.json4s/json4s-core_2.9.1/3.0.0/org/json4s/JsonAST$$JArray.html

and I've tried to use the method:

 def ++ (other: JValue): JValue

But it's not working.

 error: value ++ is not a member of object org.json4s.JsonAST.JArray
[ERROR]         recordsJArray = recordsJArray++jsonRecord

Can someone please help me? Is there any way of adding the JValue to the JArray? Thank you

Looks like you are not using same version than the doc you've linked — OlivierBlanvillain, May 04 '17 at 11:17
Hello, I'm using scala-2.10 and the version for json4s is 3.5.1 from maven repository. I've just realized the link is for 2.9.1 https://www.javadoc.io/doc/org.json4s/json4s-core_2.10/3.5.1 — jsonH, May 04 '17 at 11:35
Great, you can now answer your own question by looking at the correct documentation! — OlivierBlanvillain, May 04 '17 at 15:37
I can't find any function like ++ in documentation, that's why I've kept the question. I guess the function doesn't exist in my version, so I still need help to solve it — jsonH, May 04 '17 at 19:15
BEWARE: Json4s is [vulnerable under DoS/DoW attacks](https://github.com/json4s/json4s/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+denial)! — Andriy Plokhotnyuk, Dec 05 '19 at 07:43

score 1 · Answer 1 · answered Nov 27 '19 at 20:16

++ returns JValue, which is a supertype of JArray.

Since recordsJArray must be a JArray, the Scala compiler is looking for an implementation of ++ that returns a JArray. Since there is none, the compiler reports that your desired function is not a member of the object on which you're trying to invoke it.

Instead of relying on JsonAST's function, you can steal their implementation of ++ for your input types (JArray plus JValue):

recordsJArray = JArray(recordsJArray ::: List(jsonRecord))

Json4s add JValue to JArray

1 Answers1