In analogy to the spray-json Support spray-httpx also provides the Json4sSupport and Json4sJacksonSupport traits, which automatically provide implicit Marshaller and Unmarshaller instances for all types if an implicit org.json4s.Formats instance is in scope.
When mixing in either one of the two traits you have to implement the abstract member:
implicit def json4sFormats: Formats
with your custom logic. See the json4s documentation for more information on how to do this.