Serialize and Deserialize scala enumerations or case objects using json4s - scala

Question

Suppose I have an enumeration or sealed group of case objects as follows:
sealed abstract class Status
case object Complete extends Status
case object Failed extends Status
case object Pending extends Status
case object Unknown extends Status
or
object Status extends Enumeration {
val Complete, Failed, Pending, Unknown = Value
}
What is the easiest way to create json formats for these so that I can very easily (programmatically) generate json formats for use in a custom JsonFormat factory method, such as the following, which works for all normal case classes, strings, collections, etc., but produces {} or {"name": null} for the above two types of enumerations?:
import org.json4s.DefaultFormats
import org.json4s.jackson.JsonMethods.parse
import org.json4s.jackson.Serialization
import org.json4s.jvalue2extractable
import org.json4s.string2JsonInput
trait JsonFormat[T] {
def read(json: String): T
def write(t: T): String
}
object JsonFormat {
implicit lazy val formats = DefaultFormats
def create[T <: AnyRef: Manifest](): JsonFormat[T] = new JsonFormat[T] {
def read(json: String): T = parse(json).extract[T]
def write(t: T): String = Serialization.write(t)
}
}

Answer 1

We've used org.json4s.ext.EnumNameSerializer to serialize enumerations:
import org.json4s._
import org.json4s.ext.EnumNameSerializer
class DoesSomething {
implicit lazy val formats = DefaultFormats + new EnumNameSerializer(Status)
...stuff requiring serialization or deserialization...
}
In practice we have mixin trait that adds the implicit format and defines all of our custom serializer/desrializers:
trait OurFormaters extends Json4sJacksonSupport {
implicit lazy val json4sJacksonFormats:Formats = DefaultFormats +
UuidSerializer +
new EnumNameSerializer(Status) +
...
}
object UuidSerializer extends CustomSerializer[UUID](format =>
(
{
case JString(s) => UUID.fromString(s)
case JNull => null
},
{
case x: UUID => JString(x.toString)
}
)
)