未填充字段时播放 Json 抛出异常

Question

我有以下读取对象：

implicit val branchRead: Reads[BranchApplyRequest] = (
      (JsPath \ "act").read[String] and
      (JsPath \ "st").read[String] and
      (JsPath \ "nts").read[String] and
      (JsPath \ "bk").read[Int]
    ) (BranchApplyRequest.apply _)

问题是当这些字段之一不是来自浏览器时，我会得到一个异常并且程序失败。理想情况下，不存在的字段将可用但未定义。如何实现？

Answer 1

改用readNullable。例如，如果 act 是 Optional:

implicit val branchRead : Reads[BranchApplyRequest] = (
      (JsPath \ "act").readNullable[String] and
      (JsPath \ "st").read[String] and
      (JsPath \ "nts").read[String] and
      (JsPath \ "bk").read[Int]
    )(BranchApplyRequest.apply _)

当然你的 BranchApplyRequest 会是这样的：

case class BranchApplyRequest(act: Option[String], ...)

未填充字段时播放 Json 抛出异常

Play Json throws exception when field is not populated

scala

playframework

playframework-2.0