使用 json4s 序列化和反序列化 Scala 枚举或 case 对象

本文介绍了使用 json4s 序列化和反序列化 Scala 枚举或 case 对象的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

假设我有一个枚举或密封的 case 对象组，如下所示:

Suppose I have an enumeration or sealed group of case objects as follows:

sealed abstract class Status case object Complete extends Status case object Failed extends Status case object Pending extends Status case object Unknown extends Status

或

object Status extends Enumeration { val Complete, Failed, Pending, Unknown = Value }

为这些创建 json 格式的最简单方法是什么，以便我可以非常轻松地(以编程方式)生成用于自定义 JsonFormat 工厂方法的 json 格式，如下所示，适用于所有正常的 case 类、字符串、集合等，但为上述两种类型的枚举生成 {} 或 {"name": null} ?:

What is the easiest way to create json formats for these so that I can very easily (programmatically) generate json formats for use in a custom JsonFormat factory method, such as the following, which works for all normal case classes, strings, collections, etc., but produces {} or {"name": null} for the above two types of enumerations?:

import org.json4s.DefaultFormats import org.json4s.jackson.JsonMethods.parse import org.json4s.jackson.Serialization import org.json4s.jvalue2extractable import org.json4s.string2JsonInput trait JsonFormat[T] { def read(json: String): T def write(t: T): String } object JsonFormat { implicit lazy val formats = DefaultFormats def create[T <: AnyRef: Manifest](): JsonFormat[T] = new JsonFormat[T] { def read(json: String): T = parse(json).extract[T] def write(t: T): String = Serialization.write(t) } }

推荐答案

我们使用了 org.json4s.ext.EnumNameSerializer 来序列化枚举:

We've used org.json4s.ext.EnumNameSerializer to serialize enumerations:

import org.json4s._ import org.json4s.ext.EnumNameSerializer class DoesSomething { implicit lazy val formats = DefaultFormats + new EnumNameSerializer(Status) ...stuff requiring serialization or deserialization... }

在实践中，我们有 mixin trait，它添加了隐式格式并定义了我们所有的自定义序列化器/反序列化器:

In practice we have mixin trait that adds the implicit format and defines all of our custom serializer/desrializers:

trait OurFormaters extends Json4sJacksonSupport { implicit lazy val json4sJacksonFormats:Formats = DefaultFormats + UuidSerializer + new EnumNameSerializer(Status) + ... } object UuidSerializer extends CustomSerializer[UUID](format => ( { case JString(s) => UUID.fromString(s) case JNull => null }, { case x: UUID => JString(x.toString) } ) )