scala/liftweb序列化json [英] scala/liftweb serializing json

问题描述

我正在将net.liftweb解析器用于scala

I am using net.liftweb parser for scala

我有一个像这样的json

I have a json like this

  {
  "k1":"v1",
  "k2":["v21", "v22", "v23"]
  }

k2是一个可选字段，json可能有也可能没有.我将其提取到案例类中

k2 is an optional field, json might or might not have it. I extract this into a case class

案例类MyCC(k1:字符串，k2:列表[String])

case class MyCC (k1: String, k2: List[String])

当json转换为case类时，如果k2不存在，则将其反序列化为空列表.问题是在转换回json时，如果它是一个空列表，我如何使解析器不对该字段进行序列化.

When json is converted to case class, if k2 is not present then it is deserialized into empty list. The issue is while converting back to json, how could i make the parser not serialize this field if it is an empty list.

推荐答案

您应创建自定义序列化器.这适合您的情况:

You should create custom serializer. This should be fine for your case:

import org.json4s._
import org.json4s.native.Serialization.write
class NilSerializer extends CustomSerializer[List[String]](format => ( {
    case JNothing => Nil
  }, {
    case Nil => JNothing
}))

implicit val formats = DefaultFormats + new NilSerializer
println(write(MyCC("key", Nil)))
>> {"k1":"key"}

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