播放Map [Int，_]的JSON格式器 [英] Play JSON formatter for Map[Int,_]

问题描述

我正在尝试使用play-reactivemongo和reactmongo-extensions将Rails/Mongodb应用程序迁移到Play 2.3.在对数据建模时，我遇到了序列化和反序列化Map [Int，Boolean]的问题.

I am attempting to migrate a Rails/Mongodb application to Play 2.3 using play-reactivemongo and reactivemongo-extensions. In modeling my data I am running across a problem serializing and deserializing a Map[Int,Boolean].

当我尝试通过宏定义格式时

When I try to define my formats via macro like so

implicit val myCaseClass = Json.format[MyCaseClass]

MyCaseClass具有几个字符串字段，一个BSONObjectID字段和一个编译器抱怨的Map [Int，Boolean]字段:

where MyCaseClass has a few string fields, a BSONObjectID field, and a Map[Int,Boolean] field the compiler complains with:

No Json serializer found for type Map[Int,Boolean]. Try to implement an implicit Writes or Format for this type.
No Json deserializer found for type Map[Int,Boolean]. Try to implement an implicit Reads or Format for this type.

在Reads.scala中查看Play的源代码，我看到为Map [String，_]定义的Reads，但没有为Map [Int，_]定义的Reads.

Looking at the source code for Play in Reads.scala I see a Reads defined for Map[String,_] but none for Map[Int,_].

是否有一个原因，为什么Play对字符串映射具有默认的读/写但对于其他简单类型却没有?

Is there a reason why Play has default Read/Writes for string maps but not for other simple types?

我不完全了解play定义的Map [String，_]，因为我对scala相当陌生.我将如何将其转换为Map [Int，_]?如果由于某些技术原因无法实现，该如何定义Map [Int，Boolean]的读/写?

I don't fully understand the Map[String,_] defined by play because I am fairly new to scala. How would I go about translating that into a Map[Int,_]? If that is not possible for some technical reason how would I define a Reads/Writes for Map[Int,Boolean]?

推荐答案

您可以在游戏中编写自己的读写内容.

you can write your own reads and writes in play.

在您的情况下，看起来像这样:

in your case, this would look like this:

implicit val mapReads: Reads[Map[Int, Boolean]] = new Reads[Map[Int, Boolean]] {
    def reads(jv: JsValue): JsResult[Map[Int, Boolean]] =
        JsSuccess(jv.as[Map[String, Boolean]].map{case (k, v) =>
            Integer.parseInt(k) -> v .asInstanceOf[Boolean]
        })
}

implicit val mapWrites: Writes[Map[Int, Boolean]] = new Writes[Map[Int, Boolean]] {
    def writes(map: Map[Int, Boolean]): JsValue =
        Json.obj(map.map{case (s, o) =>
            val ret: (String, JsValueWrapper) = s.toString -> JsBoolean(o)
            ret
        }.toSeq:_*)
}

implicit val mapFormat: Format[Map[Int, Boolean]] = Format(mapReads, mapWrites)

我已经在play 2.3中对其进行了测试.我不确定在服务器端使用Map [Int，Boolean]和在客户端具有字符串->布尔映射的json对象是否是最好的方法.

I have tested it with play 2.3. I'm not sure if it's the best approach to have a Map[Int, Boolean] on server side and a json object with string -> boolean mapping on the client side, though.

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