Play框架:读取包含空值的Json

Question

我正在尝试在Play Scala程序中读取Json数据.Json在某些字段中可能包含空值,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],
                          )

这不能编译,我明白了 No Json deserializer found for type Option[String]. Try to implement an implicit Reads or Format for this type.

如何声明Reads对象接受可能的null？

Answer 1

您可以readNullable用来解析缺失或null字段:

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 _)