转换 PlayJSON 映射中的值

Question

我正在使用 PlayJson 执行 JSON 到案例 class 的标准映射。如果验证成功，我想转换映射到成员的值，Test.foo 下面。是否可以将其用于 Reads 转换器的定义？

val json = .....

case class Test(foo:String, bar:String)

val readsTest: Reads[Test] = (
  (__ \ "foo").read[String](minLength(5)) and // And I want to transform this value if the validation succeeds
  (__ \ "bar").read[String](minLength(10))
)(Test.apply _)


json.validate[Test] match {
  case s: JsSuccess[Test] => s.get
  case e: JsError => false
}

Answer 1

Reads.map 可以做到这一点，例如，假设我们想要反转 foo 字段的值，那么我们可以在 Reads 上调用 .map(v => v.reverse)所以

(__ \ "foo").read[String](minLength[String](5)).map(v => v.reverse)

这是一个工作示例

val json =
  """
    |{
    |  "foo": "abcdefghijkl",
    |  "bar": "012345678910"
    |}
    |""".stripMargin

case class Test(foo: String, bar: String)

val readsTest: Reads[Test] = (
  (__ \ "foo").read[String](minLength[String](5)).map(v => v.reverse)
  (__ \ "bar").read[String](minLength[String](10))
)(Test.apply _)

Json.parse(json).validate[Test](readsTest)

输出

JsSuccess(Test(lkjihgfedcba,012345678910),)

转换 PlayJSON 映射中的值

Transform Value In PlayJSon Mapping

scala

playframework

play-json