Akka: how to create a compact json without empty values?

Question

Is it possible with Akka (maybe some Spray "utils"?) to build a compact json feed starting from a case class like this:

case class Stuff (val1: String, val2: String, val3: String)

built in this way:

Stuff("one value", "", "another value")

and get a json in a compact form that will skip the "empty value" and will return:

{"val1" : "one value", "val3" : "another value"}

?

Answer 1

I got a simpler one but requires you to construct your case class with Option.

import spray.json._

case class Something(name: String, mid: Option[String], surname: String)

object MyJsonProtocol extends DefaultJsonProtocol {
  implicit val sthFormat = jsonFormat3(Something)
}

object Main {
  def main(args: Array[String]): Unit = {

    val sth = Something("john", None, "johnson").toJson
    println(sth) // yields {"name":"john","surname":"johnson"}

  }
}

kali's answer with custom writer might be better depending on what you need.