[英]Deserialization of case object in Scala with JSON4S
I have some case classes defined like follows: 我有一些案例类定义如下:
sealed trait Breed
case object Beagle extends Breed
case object Mastiff extends Breed
case object Yorkie extends Breed
case class Dog(name: String, breed: Breed)
I also have an endpoint defined with Scalatra: 我还有一个使用Scalatra定义的端点:
post("/dog") {
val dog = parsedBody.extract[Dog]
...
}
I'd like this JSON object: 我想要这个JSON对象:
{
name: "Spike",
breed: "Mastiff"
}
to deserialize to the appropriate instance of Dog
. 反序列化为适当的
Dog
实例。 I'm struggling to figure out how to write a custom deserializer for Breed
and register it with JSON4S. 我正在努力弄清楚如何为
Breed
编写自定义反序列化器并将其注册到JSON4S。
You need to write the serializer like below: 您需要编写如下的序列化程序:
Serializer : 串行器 :
case object BreedSerializer extends CustomSerializer[Breed](format => (
{
case JString(breed) => breed match {
case "Beagle" => Beagle
case "Mastiff" => Mastiff
case "Yorkie" => Yorkie
}
case JNull => null
},
{
case breed:Breed => JString(breed.getClass.getSimpleName.replace("$",""))
}))
Now, you will have to add this serialiser to the default formats. 现在,您必须将此序列化程序添加到默认格式。
import org.json4s.CustomSerializer
val serializers = List(BreedSerializer)
implicit lazy val serializerFormats: Formats = DefaultFormats ++ serializers
Hope this solves your problem. 希望这能解决你的问题。
You can create a CustomSerializer
for Breed
like you mentioned : 你可以像你提到的那样为
Breed
创建一个CustomSerializer
:
import org.json4s._
import org.json4s.JsonDSL._
import org.json4s.native.JsonMethods._
import org.json4s.native.Serialization
import org.json4s.native.Serialization._
object BreedSerializer extends CustomSerializer[Breed]( format => (
{
case JString("Beagle") => Beagle
case JString("Mastiff") => Mastiff
case JString("Yorkie") => Yorkie
}, {
case Beagle => JString("Beagle")
case Mastiff => JString("Mastiff")
case Yorkie => JString("Yorkie")
}
))
Which you can use as : 你可以用作:
val json1 = """{ "name": "Spike", "breed": "Yorkie" }"""
val json2 = """{ "name": "Pluto", "breed": "Mastiff" }"""
implicit val json4sFormats = Serialization.formats(NoTypeHints) + BreedSerializer
val dog1 = parse(json1).extract[Dog] // Dog(Spike,Yorkie)
val dog2 = parse(json2).extract[Dog] // Dog(Pluto,Mastiff)
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