Akka http(联合国)马歇尔特质 [英] akka http (un)marshall traits
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问题描述
我们假设以下代码:
sealed trait Action {
def run(): Boolean
}
case class SimpleAction(parameter: String) extends Actions {
// some impl
}
case class ExtendedAction(parameter1: String, parameter2: String) extends Actions {
// some impl
}
现在我想定义一个可以检索操作的Web服务。我该如何将动作编组,因为它只是特征而不是特定类型?
Now I want to define a webservice where one can retrieve the Actions. How can I Marshall the Action as it's just the trait and no specific Type?
我发现了这个 https://github.com/spray/spray-json#providing-jsonformats-for-other-types 文件。有没有比使用这种方法和模式匹配更简单的方法了?
I have found this https://github.com/spray/spray-json#providing-jsonformats-for-other-types in the Docs. Is there any simpler way to achieve this than using this approach mixed with pattern matching?
推荐答案
import spray.json._
import DefaultJsonProtocol._
implicit val simpleActionFormat = jsonFormat1(SimpleAction)
implicit val extendedActionFormat = jsonFormat2(ExtendedAction)
implicit val actionFormat1 = new JsonFormat[Action] {
override def write(obj: Action): JsValue = obj match {
case a: SimpleAction => JsObject("type" -> "simple".toJson, "value" -> a.toJson)
case b: ExtendedAction => JsObject("type" -> "extended".toJson, "value" -> b.toJson)
}
override def read(json: JsValue): Action = json.asJsObject.getFields("type", "value") match {
case Seq(JsString("simple"), js) => js.convertTo[SimpleAction]
case Seq(JsString("extended"), js) => js.convertTo[ExtendedAction]
case _ => throw new RuntimeException(s"Invalid json format: $json")
}
}
或者,如果您只关心将 Actions
转换为json,则只需:
Or if you only care about converting Actions
to json, then simply:
implicit val simpleActionFormat = jsonFormat1(SimpleAction)
implicit val extendedActionFormat = jsonFormat2(ExtendedAction)
implicit val actionFormat = lift(new JsonWriter[Action] {
override def write(obj: Action): JsValue = obj match {
case a: SimpleAction => a.toJson
case b: ExtendedAction => b.toJson
}
})
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