无法使用Circe JSON解析器创建通过JSON字符串的对象

时间：2019-04-24 14:55:27

标签： scala circe

因此，我正在尝试为要转换为域对象的JSON字符串创建自定义解码器。 我正在使用Scala / Circe遍历JSON并创建对象。 我无法运行它。我确定我不清楚如何遍历JSON。有人可以建议吗？

这是有问题的JSON，

   {
  "args": {}, 
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3", 
    "Accept-Encoding": "gzip, deflate", 
    "Accept-Language": "en-US,en;q=0.9", 
    "Host": "httpbin.org", 
    "Upgrade-Insecure-Requests": "1", 
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36"
  }, 
  "origin": "61.16.136.118, 61.16.136.118", 
  "url": "https://httpbin.org/get"
}

这是我的代码的样子，

    import com.softwaremill.sttp._
import com.softwaremill.sttp.circe._
import io.circe._, io.circe.parser._

case class Headers(Accept: String, Accept_Encoding: String, Accept_Language: String, Host: String, Upgrade_Insecure_Requests: String, User_Agent: String)
case class RootInterface(args: String, headers: Headers, origin: String, url: String)

object SttpClientGetPost extends App {
  implicit val backend = HttpURLConnectionBackend()

  implicit val rootDecoder: Decoder[RootInterface] =
    (hCursor: HCursor) => {
      val tcursor = hCursor.downField("headers")
      val argsCursor = hCursor.downField("args")
        for{
          args <- for{
          testString <-  argsCursor.get[String]("args")
        }yield testString

        headers <- for {
          Accept <- tcursor.downField("Accept").as[String]
          Accept_Encoding <- tcursor.downField("Accept-Encoding").as[String]
          Accept_Language <- tcursor.downField("Accept-Language").as[String]
          Host <- tcursor.downField("Host").as[String]
          Upgrade_Insecure_Requests <- tcursor.downField("Upgrade-Insecure-Requests").as[String]
          User_Agent <- tcursor.downField("User-Agent").as[String]
        } yield Headers(Accept, Accept_Encoding, Accept_Language, Host, Upgrade_Insecure_Requests, User_Agent)
        origin <- hCursor.downField("Origin").as[String]
        url <- hCursor.downField("url").as[String]
      } yield RootInterface("", headers, origin, url)
    }
  val secondRequest = sttp //.headers(("userId", USER_ID),("password","testpassword"))
    .get(uri"http://httpbin.org/get")

  secondRequest.send().body match {
    case Left(fail) => System.out.println("The Get request was unsuccessful.   " + fail)
    case Right(rawJSONResponse) =>
      parser.decode(rawJSONResponse) match {
        case Left(fail) => System.out.println("The JSON response could not be parsed by Circe.  " + fail)
        case Right(rootInterfaceObject) =>
          System.out.println("Origin :" + rootInterfaceObject.origin)

      }
  }

}

更新： 我现在尝试都无济于事，

case class Headers(Accept: String, Accept_Encoding: String, Accept_Language: String, Host: String, Upgrade_Insecure_Requests: String, User_Agent: String)
case class RootInterface(args: String, headers: Headers, origin: String, url: String)


val doc = """{
  "args": {}, 
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3", 
    "Accept-Encoding": "gzip, deflate", 
    "Accept-Language": "en-US,en;q=0.9", 
    "Host": "httpbin.org", 
    "Upgrade-Insecure-Requests": "1", 
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36"
  }, 
  "origin": "61.16.136.118, 61.16.136.118", 
  "url": "https://httpbin.org/get"
}"""


  implicit val decodeHeaders: Decoder[Headers] = Decoder.forProduct6(
  "Accept",
  "Accept-Encoding",
  "Accept-Language",
  "Host",
  "Upgrade-Insecure-Requests",
  "User-Agent"
 )(Headers(_, _, _, _, _, _))

implicit val decodeRootInterface: Decoder[RootInterface] = Decoder.forProduct4(
  "args",  
  "headers",
  "origin",
  "url"
)(RootInterface(_, _, _, _))

val t = decode[RootInterface](doc)

我仍然无法解码。似乎是因为args字段。

1 个答案:

答案 0 :(得分：4)

我强烈建议您以结构化方式建立您的实例，例如您可以定义一个单独的Headers实例，然后在RootInterface中使用该实例，而不是将所有Decoder[Headers]解码逻辑烘焙到Decoder[RootInterface]解码器中。

我还建议您避免直接使用游标，除非您做的特别复杂的事情知道您需要该级别的定义。

因此，给出此文档：

val doc = """{
  "args": {}, 
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3", 
    "Accept-Encoding": "gzip, deflate", 
    "Accept-Language": "en-US,en;q=0.9", 
    "Host": "httpbin.org", 
    "Upgrade-Insecure-Requests": "1", 
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36"
  }, 
  "origin": "61.16.136.118, 61.16.136.118", 
  "url": "https://httpbin.org/get"
}"""

…以及这些案例类：

case class Headers(Accept: String, Accept_Encoding: String, Accept_Language: String, Host: String, Upgrade_Insecure_Requests: String, User_Agent: String)
case class RootInterface(args: String, headers: Headers, origin: String, url: String)

…以下是您可以在REPL中使用的完整示例：

import io.circe.Decoder, io.circe.jawn.decode

implicit val decodeHeaders: Decoder[Headers] = Decoder.forProduct6(
  "Accept",
  "Accept-Encoding",
  "Accept-Language",
  "Host",
  "Upgrade-Insecure-Requests",
  "User-Agent"
 )(Headers(_, _, _, _, _, _))

implicit val decodeRootInterface: Decoder[RootInterface] = Decoder.forProduct3(
  "headers",
  "origin",
  "url"
)(RootInterface("", _, _, _))

…像这样：

scala> decode[RootInterface](doc)
res0: Either[io.circe.Error,RootInterface] = Right(RootInterface(,Headers(text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3,gzip, deflate,en-US,en;q=0.9,httpbin.org,1,Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36),61.16.136.118, 61.16.136.118,https://httpbin.org/get))

（我不确定args解码的意图是什么，所以我只是在遵循您的实现方式使用空字符串。）

但是，如果您控制Headers案例类的定义，我强烈建议您使用惯用的Scala成员名称（例如，驼峰式案例，而不是上层蛇）。在我看来，将其与circe-derivation结合在一起可以提供一个非常清晰的解决方案：

import io.circe.Decoder, io.circe.derivation.deriveDecoder

case class Headers(
  accept: String,
  acceptEncoding: String,
  acceptLanguage: String,
  host: String,
  upgradeInsecureRequests: String,
  userAgent: String
)

object Headers {
  implicit val decodeHeaders: Decoder[Headers] = deriveDecoder(
    _.replaceAll("([A-Z])", "-$1").capitalize
  )
}

case class RootInterface(
  args: Map[String, String],
  headers: Headers,
  origin: String,
  url: String
)

object RootInterface {
  implicit val decodeRootInterface: Decoder[RootInterface] = deriveDecoder
}

然后：

scala> io.circe.jawn.decode[RootInterface](doc)
res0: Either[io.circe.Error,RootInterface] = Right(RootInterface(Map(),Headers(text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3,gzip, deflate,en-US,en;q=0.9,httpbin.org,1,Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36),61.16.136.118, 61.16.136.118,https://httpbin.org/get))
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