Question

我们的状态定义为：

sealed trait Status
case object Status {
  case object StatusA extends Status
  case object StatusB extends Status
  case object StatusC extends Status
}

我们的状态如下：

val status = Status.StatusA

有没有办法（de）使用预定义的json4s fomratters序列化这种结构？

我们尝试使用defult格式化程序：

implicit val formats = new org.json4s.DefaultFormats

它不起作用。接下来，我们尝试使用ext提供的json4s和Enum支持：

implicit val formats = org.json4s.DefaultFormats + new org.json4s.ext.EnumSerializer(Status)

它再次无效。我们必须完全将sealed trait的结构更改为实际的Enumeration。有没有办法用case class es？

做到这一点

Answer 1

这是一个完整的工作示例，我更改了一些类以使示例更简单，这样您就可以使用＆＃34; name＆＃34;以不同的方式，您实际上可以省略＆＃34; def name＆＃34;，但在这种情况下，您需要稍微更改序列化程序。第二个Serializer就在下面。



    sealed trait Status {
      def name: String
    }

    case object Status {
      def apply(name: String): Status = name match {
        case StatusA.name => StatusA
        case StatusB.name => StatusB
        case StatusC.name => StatusC
        case _ => throw new UnsupportedOperationException("Unknown value")
      }
    }

    case object StatusA extends Status {
      override val name = "StatusA"
    }

    case object StatusB extends Status {
      override val name = "StatusB"
    }

    case object StatusC extends Status {
      override val name = "StatusC"
    }

    class StatusSerializer extends CustomSerializer[Status](formats =>
      ( {
        case JString(s) => Status(s)
        case JNull => throw new UnsupportedOperationException("No status specified")
      }, {
        case status: Status => JString(status.name)
      })
    )

    case class SimpleRichObject(someString: String, someInt: Int, statuses: List[Status])

    object Test extends App {
      implicit val formats = DefaultFormats + new StatusSerializer
      val obj = SimpleRichObject("Answer to life the universe and everything", 42, List(StatusA, StatusB, StatusC))

      def toCompactJsonString(any: Any) = {
        JsonMethods.compact(JsonMethods.render(Extraction.decompose(any)))
      }

      def toPrettyJsonString(any: Any) = {
        JsonMethods.pretty(JsonMethods.render(Extraction.decompose(any)))
      }

      /** To Json */
      println(s"Compact json:\n${toCompactJsonString(obj)}")
      println(s"Pretty json:\n${toPrettyJsonString(obj)}")

      /** From Json */
      val json =
        """{
          |  "someString":"Here is a another String",
          |  "someInt":1234,
          |  "statuses":["StatusA","StatusB"]
          |}""".stripMargin

      val richObj = JsonMethods.parse(json).extract[SimpleRichObject]
      println(s"Rich object toString: $richObj")
    }

这是第二个Serializer，使用第二个，你不需要在你的＆＃34; Enums＆＃34;

中定义额外的代码



    class SecondStatusSerializer extends CustomSerializer[Status](formats =>
      ( {
        case JString(s) => s match {
          case "StatusA" => StatusA
          case "StatusB" => StatusB
          case "StatusC" => StatusC
        }
        case JNull => throw new UnsupportedOperationException("No status specified")
      }, {
        case status: Status => status match {
          case StatusA => JString("StatusA")
          case StatusB => JString("StatusB")
          case StatusC => JString("StatusC")
        }
      })
    )

这就是这个人跑步时的样子，紧凑的json：

{"someString":"Answer to life the universe and everything","someInt":42,"statuses":["StatusA","StatusB","StatusC"]}

漂亮的json：

{
  "someString":"Answer to life the universe and everything",
  "someInt":42,
  "statuses":["StatusA","StatusB","StatusC"]
}

Rich object toString：SimpleRichObject（这是另一个String，1234，List（StatusA，StatusB））

Scala json4s密封了特征作为枚举

1 个答案: