在spray-json中如何解析嵌套的json数据

Question

我正在使用spray-client，希望使用spray-json（与之搭配）从谷歌地图API中获取一个经纬度对象。为此，我需要将整个响应结构设置好：

case class AddrComponent(long_name: String, short_name: String, types: List[String])
case class Location(lat: Double, lng: Double)
case class ViewPort(northeast: Location, southwest: Location)
case class Geometry(location: Location, location_type: String, viewport: ViewPort)
case class EachResult(address_components: List[AddrComponent],
                      formatted_address: String,
                      geometry: Geometry,
                      types: List[String])
case class GoogleApiResult[T](status: String, results: List[T])

object AddressProtocol extends DefaultJsonProtocol {
    implicit val addrFormat = jsonFormat3(AddrComponent)
    implicit val locFormat = jsonFormat2(Location)
    implicit val viewPortFormat = jsonFormat2(ViewPort)
    implicit val geomFormat = jsonFormat3(Geometry)
    implicit val eachResFormat = jsonFormat4(EachResult)
    implicit def GoogleApiFormat[T: JsonFormat] = jsonFormat2(GoogleApiResult.apply[T])
}
import AddressProtocol._

有没有办法从响应的json中只获取Location并避免所有这些冗长的代码？

spray-client 代码：

implicit val system = ActorSystem("test-system")
import system.dispatcher

private val pipeline = sendReceive ~> unmarshal[GoogleApiResult[EachResult]]

def getPostcode(postcode: String): Point = {
    val url = s"http://maps.googleapis.com/maps/api/geocode/json?address=$postcode,+UK&sensor=true"
    val future = pipeline(Get(url))
    val result = Await.result(future, 10 seconds)
    result.results.size match {
        case 0 => throw new PostcodeNotFoundException(postcode)
        case x if x > 1 => throw new MultipleResultsException(postcode)
        case _ => {
            val location = result.results(0).geometry.location
            new Point(location.lng, location.lat)
        }
    }
}

或者，我如何在spray-client中使用jackson？

- shmish111

---

你可以尝试使用 https://github.com/jrudolph/json-lenses/，它可以让你轻松地从 JSON 抽取数据。 - jrudolph

太棒了，需要稍微调整一下，但现在看起来很棒。这个会合并到spray-json中吗？应该的！ - shmish111

将其与spray-json合并是计划，但我们目前没有能力进行移动。 - jrudolph

Answer 1

在遵循jrudolph的建议使用json-lenses后，我进行了相当多的尝试，但最终使事情顺利运行。作为一个新手，我发现这很困难，而且我相信这个解决方案远非最优雅 - 尽管如此，我认为这可能会帮助人们或激发其他人进行改进。

给定JSON：

{
    "status": 200,
    "code": 0,
    "message": "",
    "payload": {
        "statuses": {
            "emailConfirmation": "PENDING",
            "phoneConfirmation": "DONE",
        }
    }
}

对于仅解析statuses的情况类，可以使用case class：

case class UserStatus(emailConfirmation: String, phoneConfirmation: String)

可以通过以下方式对响应进行反序列化：

import scala.concurrent.Future
import spray.http.HttpResponse
import spray.httpx.unmarshalling.{FromResponseUnmarshaller, MalformedContent}
import spray.json.DefaultJsonProtocol
import spray.json.lenses.JsonLenses._
import spray.client.pipelining._

object UserStatusJsonProtocol extends DefaultJsonProtocol {
  implicit val userStatusUnmarshaller = new FromResponseUnmarshaller[UserStatus] {
    implicit val userStatusJsonFormat = jsonFormat2(UserStatus)
    def apply(response: HttpResponse) = try {
      Right(response.entity.asString.extract[UserStatus]('payload / 'statuses))
    } catch { case x: Throwable =>
      Left(MalformedContent("Could not unmarshal user status.", x))
    }
  }
}
import UserStatusJsonProtocol._

def userStatus(userId: String): Future[UserStatus] = {
  val pipeline = sendReceive ~> unmarshal[UserStatus]
  pipeline(Get(s"/api/user/${userId}/status"))
}

- lost