Combining type and field serializers

There is now a UUID serializer provided in the extras package of json4s. It will most likely be available in version 3.2.11 (which has not been released as of this writing).

You'll be able to do something like this:

import org.json4s.ext.JavaTypesSerializersimplicit val json4sFormats = Serialization.formats(NoTypeHints) ++ JavaTypesSerializers.all

This was taken from the tests for this feature's PR.

The trick is to not write a serializer for your type, but for the type that you're using inside (in this case java.util.UUID)

Then you can add that serializer to the toolbox and from then any type using UUID will work exactly like types using DefaultSerializer supported fields did:

case object UUIDSerialiser extends CustomSerializer[UUID](format => (    {      case JString(s) => UUID.fromString(s)      case JNull => null    },    {      case x: UUID => JString(x.toString)    }  ))implicit val json4sFormats = Serialization.formats(NoTypeHints) + UUIDSerialiser

Update link to the PR

Update 2 the PR was merged, and now, in case of UUID you can use:

import org.json4s.ext.JavaTypesSerializersimplicit val json4sFormats = Serialization.formats(NoTypeHints) ++ JavaTypesSerializers.all