json4s deserialized object does not match original - scala

Question

In Scala 2.10.6, using json4s 3.2.11, to which I'm constrained for now, using the following code:
object Thing1 extends Enumeration {
type Thing1 = Value
val A = Value(0, "A")
val B = Value(1, "B")
}
object Thing2 extends Enumeration {
type Thing2 = Value
val A = Value(0, "A")
val B = Value(1, "B")
val C = Value(2, "C")
}
case class ThingHolder(thing1: Thing1, thing2: Thing2)
class ThingSpec extends FlatSpec with Matchers {
"desrialized" should "match original" in {
import org.json4s.native.Serialization.writePretty
implicit val formats = DefaultFormats + new EnumNameSerializer(Thing1) + new EnumNameSerializer(Thing2)
val original = ThingHolder(Thing1.A, Thing2.C)
println(original)
val serialized = writePretty(original)
println(serialized)
val jValue = JsonParser.parse(serialized)
val deserialized = jValue.camelizeKeys.extract[ThingHolder]
println(deserialized)
println(deserialized.thing1)
deserialized should be(original)
}
}
Results in:
ThingHolder(A,C)
{
"thing1":"A",
"thing2":"C"
}
ThingHolder(A,C)
A
ThingHolder(A,C) was not equal to ThingHolder(A,C)
This occurs with Enumeration, but not another type, for example, String. If the case class has only one Enumeration, it works fine. Why is that? I can correct this by deserializing to a case class with Strings, then mapping to the case class as I want it to be. Is there a way to coax the json4s to deserialize directly such that the deserialized object matches the original?
EDIT:
Here's the hack I mentioned to do the mapping:
case class ThingHolderSerialized(thing1: String, thing2: String)
...
val deserialized = jValue.camelizeKeys.extract[ThingHolderSerialized]
val reconstituted = ThingHolder(Thing1.withName(deserialized.thing1), Thing2.withName(deserialized.thing2))
EDIT:
Actually, the separate serializer class is unnecessary:
val deserialized = jValue.camelizeKeys.extract[ThingHolder]
val reconstituted = ThingHolder(Thing1.withName(deserialized.thing1.toString), Thing2.withName(deserialized.thing2.toString))
EDIT:
It appears that it's thing1 that's not properly deserialized, since this also builds a matching reconstituted object:
val reconstituted = deserialized.copy(thing1 = Thing1.withName(deserialized.thing1.toString))
but not this:
val reconstituted = deserialized.copy(thing2 = Thing2.withName(deserialized.thing2.toString))

Answer 1

I'm putting this out there as a solution for people that need to support json4s case class deserialization in the presence of multiple Enumerations. It's not the answer I'm looking for, but works in the meantime:
object Thing1 extends Enumeration {
type Thing1 = Value
val A = Value(0, "A")
val B = Value(1, "B")
}
object Thing2 extends Enumeration {
type Thing2 = Value
val A = Value(0, "A")
val B = Value(1, "B")
val C = Value(2, "C")
}
case class ThingHolder(thing1: Thing1, thing2: Thing2)
class ThingSpec extends FlatSpec with Matchers {
"reconstituted" should "match original" in {
import org.json4s.native.Serialization.writePretty
implicit val formats = DefaultFormats + new EnumNameSerializer(Thing1) + new EnumNameSerializer(Thing2)
val original = ThingHolder(Thing1.A, Thing2.C)
println(original)
val serialized = writePretty(original)
println(serialized)
val jValue = JsonParser.parse(serialized)
val deserialized = jValue.camelizeKeys.extract[ThingHolder]
println(deserialized)
val reconstituted = deserialized.copy(thing1 = Thing1.withName(deserialized.thing1.toString))
reconstituted should be(original)
}
}
The key is in the line where we're building reconstituted. We make a copy, and in the process, convert thing1 to a string and back to an Enumeration. Fortunately, toString works without the field being correctly deserialized.