如何从 Scala 中的 Http 响应实体解组自定义对象？

Question

我正在尝试通过 Scala 中的 akka 库从本地服务器检索一些数据。数据以 JSON 格式从服务器返回，但我无法将它们解组为自定义类型。

自定义 class 是配置文件，其中包含配置文件列表。

  case class Profile(
    Name: String,
    Surname: String,
    Mail: String,
    Age: Int,
    Town: String,

    Role: String,
    PrimaryInstr: String,
    SecondaryInstr: String,
    PrimaryGenre: String,
    SecondaryGenre: String,
    Influences: String,
    RecordLabel: String,
    GigAvailability: String,
    RehearseAvailability: String,
    RecordingExperience: String,
    MusicalAge: Int)

  case class Profiles(profiles: Vector[Profile])

我尝试使用以下代码解组到配置文件，但它无法编译因为错误

could not find implicit value for parameter um: akka.http.scaladsl.unmarshalling.Unmarshaller[ResponseEntity, Profiles]

import akka.http.scaladsl.Http
import akka.http.scaladsl.unmarshalling.Unmarshal
import akka.http.scaladsl.client.RequestBuilding.Get
import akka.http.scaladsl.model.HttpResponse

... 

def getProfiles = {
        var req = Get("http://localhost:9090/profiles")
        val responseFuture: Future[HttpResponse] = Http().singleRequest(req)
        responseFuture
          .onComplete {
            case Success(response) =>
              println(response.entity)
              //Here I want actually Unmarshall to Profiles, not to String
              var responseAsString = Unmarshal(response.entity).to[String] //Tried here with Profiles
              println(responseAsString)
            case Failure(_)   => sys.error("something wrong")
          }
           ...
      }

使用 [String] 解组代码生成此输出（缩写为“...”）。

HttpEntity.Strict(application/json,[{"Name":"Amadeus","Surname":"Rapisarda", ..., "MusicalAge":9},{"Name":"Federico","Surname":"D'Ambrosio", ..., "MusicalAge":24}]) FulfilledFuture([{"Name":"Amadeus","Surname":"Rapisarda", ..., "MusicalAge":9},{"Name":"Federico","Surname":"D'Ambrosio", ..., "MusicalAge":24}])

我怎样才能获得 Profiles 对象？提前致谢！

Answer 1

我终于找到了一个很好用的解决方案。

1 - 在 build.sbt 文件中添加这些依赖项

val AkkaVersion = "2.6.9"
val AkkaHttpVersion = "10.2.0"
libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-actor-typed" % AkkaVersion,
  "com.typesafe.akka" %% "akka-stream" % AkkaVersion,
  "com.typesafe.akka" %% "akka-http" % AkkaHttpVersion,
  "com.typesafe.akka" %% "akka-http-spray-json" % AkkaHttpVersion
)

2 - 在您的文件中添加这些导入

import akka.actor.typed.ActorSystem
import akka.actor.typed.scaladsl.Behaviors
import akka.http.scaladsl.Http
import akka.http.scaladsl.client.RequestBuilding.Get
import akka.http.scaladsl.model.{HttpResponse, StatusCodes}
import akka.http.scaladsl.unmarshalling.Unmarshal

import scala.util.{Failure, Success}
// for JSON serialization/deserialization following dependency is required:
// "com.typesafe.akka" %% "akka-http-spray-json" % "10.1.7"
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._

import scala.concurrent.Future

3 - 定义您的自定义模型（在我的例子中只有 Profile 模型）

final case class Profile(
                      Name: String,
                      Surname: String,
                      Mail: String,
                      Age: Int,
                      Town: String,

                      Role: String,
                      PrimaryInstr: String,
                      SecondaryInstr: String,
                      PrimaryGenre: String,
                      SecondaryGenre: String,
                      Influences: String,
                      RecordLabel: String,
                      GigAvailability: String,
                      RehearseAvailability: String,
                      RecordingExperience: String,
                      MusicalAge: Int)

4 - 定义您的自定义“unmarshaller”：计算您的自定义模型的属性数量，比如 n 并使用 jsonFormatn(您的自定义类型)。所以在这种情况下我们有 16 个属性 -->

implicit val profileFormat = jsonFormat16(Profile)

5 - 发出 http 请求。确保您的响应包含与您的模型匹配的 JSON 对象或 JSON 对象数组。使用此代码检索响应并将其转换为您的自定义模型。

def getProfiles = {
    
    //Make request
    var req = Get("http://localhost:9090/profiles")
    
    //Save Response in a Future object
    val responseFuture: Future[HttpResponse] = Http().singleRequest(req)
    
    //When the Future is fulfilled
    responseFuture.onComplete {


        case Success(response) =>
          //Here your code if there is a response
          
          //Convert your response body (response.entity) in a profile array. Note that it is a Future object
          var responseAsProfiles: Future[Array[Profile]]= Unmarshal(response.entity).to[Array[Profile]]
          
          //When the Future is fulfilled
          responseAsProfiles.onComplete{

            _.get match {

              case profiles: Array[Profile] => 
                //If response was a array of Profiles you can work with profiles
                profiles.foreach[Profile] { profile =>
                  println(profile)
                  profile
                }

              case _ => println("error")
            }

          }


        case Failure(_)   => 
          //Here your code if there is not a response
          sys.error("something wrong")
      }
}

希望这会对某人有所帮助！再见！

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