Use Spray Json to convert 2D sequence of Any into Json

Question

I am trying to understand Spray Json and very new to Scala. I have Seq(Seq("abc", 123, false, null), Seq("def", 45, "1234", 'C')) so a Seq[Seq[Any]]. I am not sure how to go about this and I cannot find any examples online.

case class SeqFormat(Seq[Seq[Any]]) => {
    // something that would convert to Seq[Seq[String]] 
    //which will would return a Json like this
    //[["abc", "123", "false", "null"],["def", "45", "1234", "C"]]
}

I tried

val someSeq = [["abc", "123", "false", "null"],["def", "45", "1234", "C"]]
val myObj = someSeq.toJson
// This gives me an error saying Any is not valid

I would appreciate any hints or snippets to help me understand this.

Answer 1

You could use an encoder such as:

import spray.json._
import DefaultJsonProtocol._

implicit object AnyJsonFormat extends JsonFormat[Any] {

  def write(x: Any) =
    try {
      x match {
        case n: Int    => JsNumber(n)
        case s: String => JsString(s)
        case c: Char   => JsString(c.toString)
        case _         => JsString("null")
      }
    } catch {
      case _: NullPointerException => JsString("null")
    }

  def read(value: JsValue) = ???
}

Which you can use as follow:

val input = Seq(Seq("abc", 123, false, null), Seq("def", 45, "1234", 'C'))
println(input.toJson)

In order to get:

[["abc",123,"null","null"],["def",45,"1234","C"]]

---

This is an adapted version of this post: Serialize Map[String, Any] with spray json

Notice the NullPointerException handling for the null case.