Question

我的案例类具有超过22个参数。

case class Model(a1: Int,
                   a2: Int,
                   a3: Int,
                   a4: Int,
                   a5: Int,
                   a6: Int,
                   a7: Int,
                   a8: Int,
                   a9: Int,
                   a10: Int,
                   a11: Int,
                   a12: Int,
                   a13: Int,
                   a14: Int,
                   a15: Int,
                   a16: Int,
                   a17: Int,
                   a18: Int,
                   a19: Int,
                   a20: Int,
                   a21: Int,
                   a22: Int,
                   a23: Int,
                   a24: Int)

我收到一个json输入，需要将其反序列化为上述Model case类。但是，我的输入json不包含字段a1和a2。我的json看起来像这样

  {
  "a3": 3,
  "a4": 4,
  "a5": 5,
  "a6": 6,
  "a7": 7,
  "a8": 8,
  "a9": 9,
  "a10": 10,
  "a11": 11,
  "a12": 12,
  "a13": 13,
  "a14": 14,
  "a15": 15,
  "a16": 16,
  "a17": 17,
  "a18": 18,
  "a19": 19,
  "a20": 20,
  "a21": 21,
  "a22": 22,
  "a23": 23,
  "a24": 24
}

现在，为了适应这种情况，我编写了自定义json读取器，该读取器将为json中的a1和a2字段添加一些虚拟值。

我有一个自定义方法，可将字段添加到读取的输入json中。扩展方法addField如下

implicit class ReadOps[A](reads: Reads[A]) {
    def addField(fieldName: String, value: Int): Reads[A] = Reads {
      json: JsValue =>
        json
          .validate(__.json.update((__ \ fieldName).json.put(JsString(value.toString))))
          .map(_.asInstanceOf[A])
    }
  }

我的隐式json格式如下

 implicit val jsonFormat = new OFormat[Model] {

    override def reads(json: JsValue): JsResult[Model] = {
      Jsonx.formatCaseClass[Model].addField("a1",1).addField("a2",2).reads(json)
    }

    override def writes(o: Model): JsObject = {
      Jsonx.formatCaseClass[Model].writes(o)
    }
  }

我面临的问题

尽管调用方法addField两次（我试图添加值为1的a1和值为2的a2），但只有值为a1的字段1被添加到json中，而a2为忽略了。而且json不会反序列化到模型案例类。

我正在使用以下依赖项

libraryDependencies += "ai.x" %% "play-json-extensions" % "0.30.1"

请让我知道该方法在哪里出错。任何指针将非常有帮助。在此先感谢!!!

注意：请不要建议在模型案例类中添加诸如将a1和a2添加为字段的解决方案。这是毫无疑问的，因为我的实际问题非常复杂，并且关于stackoverflow的问题是当前问题的非常简化的版本。

Answer 1

通过adding a field in a new branch考虑JsPath.update：

 val js = Json.obj("key1" -> "value1", "key2" -> "value2")
 js.validate(__.json.update((__ \ 'key3).json.put(JsString("value3"))))
 => JsSuccess({"key1":"value1","key2":"value2","key3":"value3"},)

这是一个可行的例子

import ai.x.play.json.Jsonx
import play.api.libs.json.Json
import play.api.libs.json._

case class Foo(a1: Int, a2: Int, a3: Int, a4: Int, a5: Int, a6: Int, a7: Int, a8: Int, a9: Int, a10: Int, a11: Int, a12: Int, a13: Int, a14: Int, a15: Int, a16: Int, a17: Int, a18: Int, a19: Int, a20: Int, a21: Int, a22: Int, a23: Int, a24: Int)

object Foo {
  implicit val format = Jsonx.formatCaseClass[Foo]
}

object AddFieldsToDeserialisation extends App {
  val raw =
    """
      |{
      |  "a3": 3,
      |  "a4": 4,
      |  "a5": 5,
      |  "a6": 6,
      |  "a7": 7,
      |  "a8": 8,
      |  "a9": 9,
      |  "a10": 10,
      |  "a11": 11,
      |  "a12": 12,
      |  "a13": 13,
      |  "a14": 14,
      |  "a15": 15,
      |  "a16": 16,
      |  "a17": 17,
      |  "a18": 18,
      |  "a19": 19,
      |  "a20": 20,
      |  "a21": 21,
      |  "a22": 22,
      |  "a23": 23,
      |  "a24": 24
      |}
    """.stripMargin


  val json = Json.parse(raw)
  val updatePutTransformation = 
    (field: String, value: Int) =>  __.json.update((__ \ field ).json.put(JsNumber(value)))
  val addedFields =
    List("a1" -> 1, "a2" -> 2)
      .map { case (field, value) => updatePutTransformation(field, value) }
      .reduce((putUpdate1, putUpdate2) => putUpdate1 andThen putUpdate2 )
  val jsonWithPutValue = json.transform(addedFields)
  println(jsonWithPutValue.get)
  println(jsonWithPutValue.get.as[Foo])


}

应输出

{ "a1": 1, "a2": 2, "a3": 3, "a4": 4, "a5": 5, "a6": 6, "a7": 7, "a8": 8, "a9": 9, "a10": 10, "a11": 11, "a12": 12, "a13": 13, "a14": 14, "a15": 15, "a16": 16, "a17": 17, "a18": 18, "a19": 19, "a20": 20, "a21": 21, "a22": 22, "a23": 23, "a24": 24 }

Foo(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24)

使用play-json-extensions对json反序列化后添加其他字段

1 个答案: