结构化scala案例类的自定义json序列化

abstract class Message
case class CardDrawn(player: Long,card: Int,mType: String = "CardDrawn") extends Message
case class CardSet(cards: List[CardDrawn],mType: String = "CardSet") extends Message

为了让CardSet与jackson scala模块一起往返于json,我使用了一个用java编写的自定义序列化器/反序列化器：

object ScrumGameMashaller {

  val mapper = new ObjectMapper() 
  val module = new SimpleModule("CustomSerializer")
  module.addSerializer(classOf[CardSet],new CardSetSerializer)
  module.addDeserializer(classOf[CardSet],new CardSetDeserializer)
  val scalaModule = DefaultScalaModule
  mapper.registerModule(scalaModule)
  mapper.registerModule(module)

  def jsonFrom(value: Any): String = {
    import java.io.StringWriter
    val writer = new StringWriter()
    mapper.writeValue(writer,value)
    writer.toString
  }

  private[this] def objectFrom[T: Manifest](value: String): T =
    mapper.readValue(value,typeReference[T])

  private[this] def typeReference[T: Manifest] = new TypeReference[T] {
    override def getType = typeFromManifest(manifest[T])
  }

  private[this] def typeFromManifest(m: Manifest[_]): Type = {
    if (m.typeArguments.isEmpty) { m.runtimeClass }
    else new ParameterizedType {
      def getRawType = m.runtimeClass
      def getActualTypeArguments = m.typeArguments.map(typeFromManifest).toArray
      def getOwnerType = null
    }
  }

使用序列化器：

public class CardSetSerializer extends JsonSerializer<CardSet> {
@Override
    public void serialize(CardSet cardSet,JsonGenerator jgen,SerializerProvider provider) throws IOException,JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeArrayFieldStart("cards");
        List<CardDrawn> cardsDrawn = cardSet.cards();
        scala.collection.Iterator<CardDrawn> iter = cardsDrawn.iterator();
        while(iter.hasNext()){
            CardDrawn cd = iter.next();
            cdSerialize(jgen,cd);
        }
        jgen.writeEndArray();
        jgen.writeStringField("mType","CardSet");
        jgen.writeEndObject();      
    }

    private void cdSerialize(JsonGenerator jgen,CardDrawn cd) throws IOException,JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeNumberField("player",cd.player());
        jgen.writeNumberField("card",cd.card());
        jgen.writeEndObject();
    }
}

和匹配的反序列化器：

public class CardSetDeserializer extends JsonDeserializer<CardSet> {

    private static class CardDrawnTuple {
        Long player;
        Integer card;
    }

    @Override
    public CardSet deserialize(JsonParser jsonParser,DeserializationContext cxt) throws IOException,JsonProcessingException {
        ObjectCodec oc = jsonParser.getCodec();
        JsonNode root = oc.readTree(jsonParser);
        JsonNode cards = root.get("cards");
        Iterator<JsonNode> i = cards.elements();
        List<CardDrawn> cardObjects = new ArrayList<>();
        while( i.hasNext() ){
            CardDrawnTuple t = new CardDrawnTuple();
            ObjectNode c = (ObjectNode) i.next();
            Iterator<Entry<String,JsonNode>> fields = c.fields();
            while( fields.hasNext() ){
                Entry<String,JsonNode> f = fields.next();
                if( f.getKey().equals("player")) {
                    t.player = f.getValue().asLong();
                } else if( f.getKey().equals("card")){
                    t.card = f.getValue().asInt();
                } else { 
                    System.err.println(CardSetDeserializer.class.getCanonicalName()+ " : unknown field " + f.getKey());
                }
            }
            CardDrawn cd = new CardDrawn(t.player,t.card,"CardDrawn");
            cardObjects.add(cd);
        }

        return new CardSet(JavaConversions.asScalaBuffer(cardObjects).toList(),"CardSet");
    }

}

这似乎是很多代码来处理scala中相当普通的东西.这段代码可以改进吗(我想念杰克逊必须做些什么)？否则有一个库会自动执行结构化案例类？ jerkson的例子看起来很简单,但似乎已经放弃了.