从多个 Json 字段创建单个子字段并使用 Play-json 应用于生成的对象

Question

我正在尝试使用 play-json 读取将以下 Json 转换为结果案例 class。但是，我坚持使用语法将经度和纬度 json 值转换为 Point 对象，同时将其余 json 值转换为相同的结果 BusinessInput 对象。这在语法上可能吗？

case class BusinessInput(userId: String, name: String, location: Point, address: Option[String], phonenumber: Option[String], email: Option[String])

object BusinessInput {

  implicit val BusinessInputReads: Reads[BusinessInput] = (
    (__ \ "userId").read[String] and
    (__ \ "location" \ "latitude").read[Double] and
      (__ \ "location" \ "longitude").read[Double]
    )(latitude: Double, longitude: Double) => new GeometryFactory().createPoint(new Coordinate(latitude, longitude))

Answer 1

从根本上说，Reads[T] 只需要一个将元组转换为 T 实例的函数。因此，给定 location JSON 对象，您可以为 Point class 编写一个，如下所示：

implicit val pointReads: Reads[Point] = (
  (__ \ "latitude").read[Double] and
  (__ \ "longitude").read[Double]      
)((lat, lng) => new GeometryFactory().createPoint(new Coordinate(lat, lng))

然后将其与 BusinessInput class:

的其余数据合并

implicit val BusinessInputReads: Reads[BusinessInput] = (
  (__ \ "userId").read[String] and
  (__ \ "name").read[String] and
  (__ \ "location").read[Point] and
  (__ \ "address").readNullable[String] and
  (__ \ "phonenumber").readNullable[String] and
  (__ \ "email").readNullable[String]
)(BusinessInput.apply _)

在第二种情况下，我们使用 BusinessInput classes apply 方法作为捷径，但您可以轻松地使用 (userId, name, point) 和创建一个省略了可选字段的字段。

如果您不想 Point 单独阅读，只需使用相同的原则将它们组合起来：

implicit val BusinessInputReads: Reads[BusinessInput] = (
  (__ \ "userId").read[String] and
  (__ \ "name").read[String] and
  (__ \ "location").read[Point]((
    (__ \ "latitude").read[Double] and
    (__ \ "longitude").read[Double]
  )((lat, lng) => new GeometryFactory().createPoint(new Coordinate(lat, lng)))) and
  (__ \ "address").readNullable[String] and
  (__ \ "phonenumber").readNullable[String] and
  (__ \ "email").readNullable[String]
)(BusinessInput.apply _)

从多个 Json 字段创建单个子字段并使用 Play-json 应用于生成的对象

Create Single sub Field from multiple Json Fields and apply to resulting Object using Play-json

scala

playframework

playframework-2.0

play-json