如何解析从 HTTP 接收的 Json 字符串并遍历值

Question

我正在使用 Scala 和 Swagger，我需要帮助弄清楚如何遍历 json 中的值并将这些值用于检查和其他操作。

HTTP get 请求后返回的 json 字符串如下所示：

{
"count": 3,
"items": [
  {
    "Id": "fd0a9e5a",
    "DbName": "Xterior Prod",
    "Name": "XP"
  },
  {
   "Id": "4158a1a6",
   "DbName": "Invidibi Pappear",
   "Name": "ISP"
  },
  {
   "Id": "7e0c57046d3f",
   "DbName": "Multi Test",
   "Name": "MMP"
  }]
}

我的 UI 允许用户输入 ID。我要做的是遍历从 API 返回的 Json 值，并找到与输入的 ID 匹配的值。找到匹配项后，我必须检查数据库中是否包含“Test”关键字。如果是这样，我将需要显示 DbName 和短名称。

我在这里找到了一些指南（例如Foreach with JSON Arrays in Play2 and Scala），但它对我不起作用。当我运行我的代码时，我得到了这个错误：

play.api.libs.json.JsResultException: JsResultException(errors:List(((0)/Id,List(ValidationError(List(error.path.missing),WrappedArray()))), ((0)/DbName,List(ValidationError(List(error.path.missing),WrappedArray()))), ((1)/Id,List(ValidationError(List(error.path.missing),WrappedArray()))), ((1)/DbName,List(ValidationError(List(error.path.missing),WrappedArray()))), ((2)/Id,List(ValidationError(List(error.path.missing),WrappedArray()))), ((2)/DbName,List(ValidationError(List(error.path.missing),WrappedArray()))), 

这是我的代码：

case class DBInfo(Id: String, DbName: String, Name: String)
contentType = "application/json"
    //get json from http

    val httpClient = HttpClients.createDefault()
    val httpResponse = httpClient.execute(new HttpGet("http://www.customers.com/dbInfo"))
    val entity = httpResponse.getEntity

    val content = fromInputStream(httpResponse.getEntity.getContent()).getLines().mkString

    implicit val dbReader = Json.reads[DBInfo]
    val dbList = (Json.parse(content) \ "items").as[List[DBInfo]]
    dbList.foreach { dbI =>
      if (dbI.Id == id)
        if (dbI.DbName.contains("Test"))
          println(dbI.DbName + " - " + dbI.Name)
          else BadRequest("Not allowed")
      else
        BadRequest("ID not found")
    }

id 是保存用户输入的 ID 的变量。有人可以告诉我为什么会出现错误以及如何解决吗？谢谢。

注意：请使用 import org.json4s.JsonAST 或 import play.api.libs.json

Answer 1

已经得到了答案。所以我就是这样做的：

case class databaseInfo(Id: String, DbName: String, Name: String)
class dbInfo{
def CheckDb(id: String): Option[String] = {
    val httpClient = HttpClients.createDefault()
    val httpResponse = httpClient.execute(new HttpGet("http://example.com"))
    val content = fromInputStream(httpResponse.getEntity.getContent()).getLines().mkString

    val envItems = (parse(content) \\ "items").children
    for (items <- envItems) {
      val dbItems = items.extract[databaseInfo]
      if (dbItems.EnvId == Some(id)) {
        if (equalsIgnoreCase(dbItems.DbName.mkString, "Test")) //do something
        else //do something
      }
    }
    None
  }
}

Answer 2

这是一种使用circe 的方法。您可以使用光标导航 JSON，并使用 Decoder[A] 类型类解码为 Environment 列表。请注意，您使用的是 Either[Failure, A] 值。

import io.circe._

case class Environment(id: String, dbName: String, name: String)

implicit val environmentDecoder: Decoder[Environment] = Decoder.instance[Environment] {
  json =>
    for {
      id <- json.downField("Id").as[String]
      dbName <- json.downField("DbName").as[String]
      name <- json.downField("Name").as[String]
    } yield {
      Environment(id, dbName, name)
    }
}

// alternatively:
// implicit val environmentDecoder: Decoder[Environment] =
//   Decoder.forProduct3[String, String, String, Environment]("Id", "DbName", "Name")(Environment.apply)


val text =
  """{
    |  "count": 3,
    |  "items": [{
    |    "Id": "fd0a9e5a",
    |    "DbName": "Xterior Prod",
    |    "Name": "XP"
    |  }, {
    |    "Id": "4158a1a6",
    |    "DbName": "Invidibi Pappear",
    |    "Name": "ISP"
    |  }, {
    |    "Id": "7e0c57046d3f",
    |    "DbName": "Multi Match Test",
    |    "Name": "MMP"
    |  }]
    |}
  """.stripMargin

val json = parser.parse(text).fold(_ => ???, json => json)


val res: Either[DecodingFailure, List[Environment]] = json.hcursor.downField("items").as[List[Environment]]


println(res)
// Right(List(Environment(fd0a9e5a,Xterior Prod,XP), Environment(4158a1a6,Invidibi Pappear,ISP), Environment(7e0c57046d3f,Multi Match Test,MMP)))


// or simply
// val res2 = parser.parse(text).right
//   .flatMap(_.hcursor.downField("items").as[List[Environment]])

你也可以使用http4s'http4s-blaze-client和http4s-circe来做HTTP请求：

import org.http4s._
import org.http4s.circe._
import scalaz.concurrent._

val client = org.http4s.client.blaze.defaultClient

val fetchEnvironments: Task[List[Environment]] =
  client.fetchAs[Json](Request(Method.GET, Uri.uri("http://example.com")))
    .flatMap { json =>
      json.hcursor.downField("items").as[List[Environment]].fold(
        failure => Task.fail(failure),
        xs => Task.now(xs)
      )
    }

val xs = fetchEnvironments.unsafePerformSync