Scala读取JSON文件

Question

i want to extract a json file in Scala like this:

val json: JsValue = Json.parse("""
{
"Received":"2015-12-29T00:00:00.000Z",
"Created":"2015-12-29T00:00:00.000Z",
"Location":{
  "Created":"2015-12-29T00:00:00.000Z",
  "Coordinate":{
      "Latitude":45.607807,
      "Longitude":-5.712018},
      },
"Infos":[],
"DigitalInputs":[{
        "TypeId":145,
        "Value":false,
        "Index":23
        }],
      }
                               """)

and this is my Scala code:

import org.apache.flink.api.scala._
import play.api.libs.json._

case class DInputs(
                  TypeId: Option[Int],
                  Value: Option[Boolean],
                  Index: Option[Int]
                  )

case class myjson (
                  Received: String,
                  Created: String,
                  Location: Option[String],
                  Infos: Option[String],
                  DigitalInputs: Option[List[DInputs]],
                  )

implicit val DInputsRead: Reads[Option[DInputs]] = (
    (__ \ "TypeId").readNullable[Int] andThen
    (__ \ "Value").readNullable[Boolean] andThen
    (__ \ "Index").readNullable[Int]
  )(DInputs.apply _)

case Some(json.DInputsRead) => println(json.DInputsRead)

The error in my code: Expression of type Reads[Option[Int]] doesn´t conform to expected type Reads[Option[DInputs]]

i´m newbie and don´t understand where is the problem, and i don´t know if this is the best way to read a json file, so any help is appreciate.Thank you.

Answer 1

There are a few issues with your input and your solution:

1. Your input JSON is invalid: it contains excessive commas in two places: right after Location object and right after DigitalInputs object. You can validate your JSONs here .
2. Your Reads instance could be shortened significantly by using Json.reads method.
3. You're missing a Reads instance for your myjson class.
4. You're missing a case class for a Location object.

Here is a complete example of parsing your input JSON to a regular Scala case class:

  import play.api.libs.json.Json

  case class MyJson(Received: String,
                    Created: String,
                    Location: Option[Location],
                    Infos: Option[List[String]],
                    DigitalInputs: Option[List[DigitalInputs]])

  case class Location(Created: String,
                      Coordinate: Coordinate)

  case class Coordinate(Latitude: Double,
                        Longitude: Double)

  case class DigitalInputs(TypeId: Option[Int],
                           Value: Option[Boolean],
                           Index: Option[Int])

  implicit val digitalInputsReads = Json.reads[DigitalInputs]
  implicit val coordinateReads = Json.reads[Coordinate]
  implicit val locationReads = Json.reads[Location]
  implicit val myJsonReads = Json.reads[MyJson]

  val inputJson = Json.parse(
    """
      |{
      |  "Received":"2015-12-29T00:00:00.000Z",
      |  "Created":"2015-12-29T00:00:00.000Z",
      |  "Location":{
      |    "Created":"2015-12-29T00:00:00.000Z",
      |    "Coordinate":{
      |      "Latitude":45.607807,
      |      "Longitude":-5.712018
      |    }
      |  },
      |  "Infos":[
      |
      |  ],
      |  "DigitalInputs":[
      |    {
      |      "TypeId":145,
      |      "Value":false,
      |      "Index":23
      |    }
      |  ]
      |}
    """.stripMargin
  )

  val myJsonInstance: MyJson = inputJson.as[MyJson]
  val longitude: Option[Double] = myJsonInstance.Location.map(_.Coordinate.Longitude) // Some(-5.712018)
  val typeId: Option[Int] = myJsonInstance.DigitalInputs.flatMap(_.headOption.flatMap(_.TypeId)) // Some(145)