Jackson Serialise a Scala Set

Question

I have a question related to fasterxml jackson in serialising a scala class Genre with a Set as one of the fields Set[Type] where Type is a case class with single param value

class Type(val value: String) extends AnyVal
case class Genre(name: String, types: Set[Type])

When I try to serialise it , it gives something like

{"genre":{"name":"xxxxxx","types":[{"value":"aaaaa"}, {"value":"bbbb"}, {"value":"ccccc"}]}}

But I don't want the generated json to contain the param name of the class and it should contain only param value . It should simply look like a comma separated values ["aaaaa","bbbb","ccccc"] something like

{"genre":{"name":"xxxxxx","types":["aaaaa","bbbb","ccccc"]}}

Is there any way , using jackson, to serialise a Set of classes with simply values in it but not param names ?

My mapper looks like this

  private val mapper = new ObjectMapper
  mapper.registerModule(DefaultScalaModule)

Thanks in Advance !

Answer 1

It should simply look like a comma separated values ["aaaaa","bbbb","ccccc"]

That is Set[String], but what you have is Set[Type]. Jackson is doing exactly what it's supposed to do. You need to change your class signature to:

case class Genre(name: String, types: Set[String])

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule

object TestObject {
  def main(args: Array[String]): Unit = {
    val mapper = new ObjectMapper()
    mapper.registerModule(DefaultScalaModule)

    val genre = Genre("xxxxxx", Set(new Type("aaaaa"), new Type("bbbb"), new Type("ccccc")))
    println("Genre:        " + mapper.writeValueAsString(genre))

    val anotherGenre = AnotherGenre("xxxxxx", Set("aaaaa", "bbbb", "ccccc"))
    println("AnotherGenre: " + mapper.writeValueAsString(anotherGenre))

  }
}

class Type(val value: String) extends AnyVal

case class Genre(name: String, types: Set[Type])

case class AnotherGenre(name: String, types: Set[String])

Output:

Genre:        {"name":"xxxxxx","types":[{"value":"aaaaa"},{"value":"bbbb"},{"value":"ccccc"}]}
AnotherGenre: {"name":"xxxxxx","types":["aaaaa","bbbb","ccccc"]}