scala - Play Framework : read Json containing null values

Question

我正在尝试在我的 Play Scala 程序中读取 Json 数据。 Json 可能在某些字段中包含空值，所以这就是我定义 Reads 对象的方式:

  implicit val readObj: Reads[ApplyRequest] = (
      (JsPath \ "a").read[String] and
      (JsPath \ "b").read[Option[String]] and
      (JsPath \ "c").read[Option[String]] and
      (JsPath \ "d").read[Option[Int]]
    )  (ApplyRequest.apply _) 

和 ApplyRequest 案例类:

case class ApplyRequest ( a: String,
                          b: Option[String],
                          c: Option[String],
                          d: Option[Int],
                          )

这不编译，我得到 No Json deserializer found for type Option[String]. Try to implement an implicit Reads or Format for this type.
如何声明 Reads 对象以接受可能的空值？

Answer 1

您可以使用 readNullable 解析丢失或 null领域:

implicit val readObj: Reads[ApplyRequest] = (
  (JsPath \ "a").read[String] and
  (JsPath \ "b").readNullable[String] and
  (JsPath \ "c").readNullable[String] and
  (JsPath \ "d").readNullable[Int]
)  (ApplyRequest.apply _)