Scala Play Json-如何从数组中的元素读取单个元素？

Question

I am have this json object

val jsonObject = """
 {
  "name" : "camara",
  "project" : {
    "key" : "DOC",
    "name" : "Dockerfiles"
  },
  "cloneUrl" : "https://server/scm/doc/camara.git",
  "links" : {
    "clone" : [ {
      "href" : "https://server/scm/doc/camara.git",
      "name" : "http"
    }, {
      "href" : "ssh://git@server:7999/doc/camara.git",
      "name" : "ssh"
    } ],
    "self" : [ {
      "href" : "url1"
    },
    {
      "href" : "url2"
    } ]
  }
}
"""

And with this case class and Reader:

case class Project(name: String, project: String, projectUrl: List[String])

implicit val projectReader: Reads[Project] = (
  (JsPath \ "name").read[String] and
  (JsPath \ "project" \ "name").read[String] and
  (JsPath \ "links" \ "self" \\ "href").read[List[String]])(Project.apply _)

I try to parse to this model:

Json.parse(jsonObject).validate[Project] match {
  case value: JsSuccess[Project] =>
     println(" >> " + value.get)
  case error: JsError =>
    println(error)
}

The I get this error

JsError(List((/links/self//href,List(ValidationError(error.path.result.multiple,WrappedArray())))))

I have no idea how to extract those hrefs from the self array into the Project class to look like this:

Project(camara,Dockerfiles,List(url1, url2))

I have looked everywhere, on the internet for a simple example that would help me on the right track, but I haven't managed to find anything that helps.

How can I solve this issue without changing my Project class's structure ?

Answer 1

  import play.api.libs.json._
  import play.api.libs.functional.syntax._
  val jsonObject = """
  {
    "name" : "camara",
    "project" : {
      "key" : "DOC",
      "name" : "Dockerfiles"
    },
    "cloneUrl" : "https://server/scm/doc/camara.git",
    "links" : {
      "clone" : [ {
        "href" : "https://server/scm/doc/camara.git",
        "name" : "http"
      }, {
        "href" : "ssh://git@server:7999/doc/camara.git",
        "name" : "ssh"
      } ],
      "self" : [ {
        "href" : "url1"
      },
      {
        "href" : "url2"
      } ]
    }
  }
  """
  case class Project(name: String, project: String, projectUrl: List[String])

  def multiUrls[T](implicit rt: Reads[T]) = Reads[List[T]] { js =>
    val l: List[JsValue] = (__ \ "links" \ "self" \\ "href")(js)
    Json.fromJson[List[T]](JsArray(l))
  }

implicit val projectReader: Reads[Project] = (
  (JsPath \ "name").read[String] and
  (JsPath \ "project" \ "name").read[String] and
  multiUrls[String])(Project.apply _)

  Json.parse(jsonObject).validate[Project] match {
    case value: JsSuccess[Project] =>
       " >> " + value.get
    case error: JsError =>
      error.toString
  }
  // >> Project(camara,Dockerfiles,List(url1, url2))

Answer 2

In your case the JSON object's structure does not map 1:1 onto the case class: Below "self" there is another object (with the "href" property), but this level is missing in your case class.

So you could modify your JSON data or the case class.

If you want to preserve both, you can parse into a "parse only" case class, and convert this one into the "target" case class after parsing:

  case class Url(href: String)

  case class ParseProject0(
    name: String,
    project: String,
    projectUrl: List[Url]) {

    def toProject: Project = {
      Project(name, project, projectUrl.map(_.href))
    }
  }

  implicit val urlReader: Reads[Url] = (
    (JsPath \ "href").read[String].map(v => Url(v)))

  implicit val projectReader: Reads[ParseProject] = (
    (JsPath \ "name").read[String] and
      (JsPath \ "project" \ "name").read[String] and
      (JsPath \ "links" \ "self").read[List[Url]])(ParseProject.apply _)

  val parsed = Json.parse(jsonObject)
  val result = parsed.validate[ParseProject] match {
    case value: JsSuccess[ParseProject] =>
      val p = value.get.toProject
      p

    case error: JsError =>
      error
  }

Anyway, looking at your "clone" property in your JSON object, it seems that you need that additional class Url anyway, as that object contains more than one property.