How to represent optional fields in spray-json?
You might have to create an explicit format (warning: psuedocodish):
object SearchRequestJsonProtocol extends DefaultJsonProtocol {
implicit object SearchRequestJsonFormat extends JsonFormat[SearchRequest] {
def read(value: JsValue) = value match {
case JsObject(List(
JsField("url", JsString(url)),
JsField("nextAt", JsString(nextAt)))) =>
SearchRequest(url, Some(new Instant(nextAt)))
case JsObject(List(JsField("url", JsString(url)))) =>
SearchRequest(url, None)
case _ =>
throw new DeserializationException("SearchRequest expected")
}
def write(obj: SearchRequest) = obj.nextAt match {
case Some(nextAt) =>
JsObject(JsField("url", JsString(obj.url)),
JsField("nextAt", JsString(nextAt.toString)))
case None => JsObject(JsField("url", JsString(obj.url)))
}
}
}
Works for me (spray-json 1.1.1 scala 2.9.1 build)
import cc.spray.json._
import cc.spray.json.DefaultJsonProtocol._
// string instead of date for simplicity
case class SearchRequest(url: String, nextAt: Option[String])
// btw, you could use jsonFormat2 method here
implicit val searchRequestFormat = jsonFormat(SearchRequest, "url", "nextAt")
assert {
List(
"""{"url":"..."}""",
"""{"url":"...", "nextAt":null}""",
"""{"url":"...", "nextAt":"2012-05-30T15:23Z"}""")
.map(_.asJson.convertTo[SearchRequest]) == List(
SearchRequest("...", None),
SearchRequest("...", None),
SearchRequest("...", Some("2012-05-30T15:23Z")))
}