Scala：使用 playframework 将部分 Json 映射到对象

Question

I'm relatively new to Scala. I would like to map part of my Json to my Object. Code looks like this:

    def seasons = (json \\ "season")

case class:

  case class Season(startDate: LocalDate, endDate: LocalDate)

json-structure:

[
      {
        "id": "",
        "name": "",
        "season": {
          "start": "0",
          "end": "0"
        }
      }
]

I would somehow like to end up with a List[Season], so I can loop through it.

Question #2

json-structure:

[
      {
        "id": "",
        "name": "",
        "season": {
          "start": "0",
          "end": "0"
        }
      },
      {
        "id": "",
        "name": "",
        "season": {
          "start": "0",
          "end": "0"
        }
      }...
]

Json (which is a JsValue btw) brings multiple regions as can be seen above. Case classed are provided (Region holds a Season), naming is the same as in json. Formats look like this:

implicit val seasonFormat: Format[Season] = Json.format[Season]
implicit val regionFormat: Format[Region] = Json.format[Region]

So what would I need to call in order to get a List[Region]? I thought of something like regionsJson.as[List[Region]] as I defined the Format, which provides me the Read/Write possibilities. But unfortunately, it's not working.

What is the best way doing this? I've tried it with an JsArray, but I have difficulties with mapping it...

Any input would be much appreciated!

Answer 1

I've added some changes to your original case class and renamed its fields to match json fields.

The following code does parsing of the json into Seq[Session]

import java.time.LocalDate
import play.api.libs.json._

case class Season(start: LocalDate, end: LocalDate)
implicit val sessionFormat: Format[Season] = Json.format[Season]

val json =
  """
    |[
    |      {
    |        "id": "",
    |        "name": "",
    |        "season": {
    |          "start": "2020-10-20",
    |          "end": "2020-10-22"
    |        }
    |      }
    |]
    |""".stripMargin

val seasonsJson: collection.Seq[JsValue] = Json.parse(json) \\ "season"
val seasons: collection.Seq[Season] = seasonsJson.map(_.as[Season])
seasons.foreach(println)

Please note that I changed the data of your json and instead of 0 , which is not a valid date, I provided dates in iso format yyyy-mm-dd .

The above code works with play-json version 2.9.0.

---UPDATE---

Following up comment by @cchantep.

Method as will produce an exception if json cannot be mapped in case class, a non-exception option is to use asOpt that does not throw an exception but returns a None if mapping is not possible.