How could I properly work with Scala Play Read?

Question

According to this documentation (official):

https://www.playframework.com/documentation/2.8.x/ScalaJsonCombinators

I have to create a case class, after that I have to create a JsonReader:

val nameReads: Reads[String] = (JsPath \ "name").read[String]

then

val nameResult: JsResult[String] = json.validate[String](nameReads)

So, the result would be into nameResult and it was expecting that data was accessible like this:

println(nameResult.name)

Unfortunately, it doesn't work. It doesn't print results or return them. First of all I work with Future and read JSON from web

implicit val context = scala.concurrent.ExecutionContext.Implicits.global

val userReads: Reads[User] = (
  (JsPath  \ "id").read[Int] and
  (JsPath  \ "login").read[String]
)

val futureResult = wc.url(path).get().map {
  response =>
    response.json.validate[User](userReads)
}

futureResult.map(r => println(r.id, r.login))

But! This code works, but it isn't in documentation.

implicit val context = scala.concurrent.ExecutionContext.Implicits.global

val userReads: Reads[User] = (
  (JsPath  \ "id").read[Int] and
  (JsPath  \ "login").read[String]
)

val futureResult = wc.url(path).get().map {
  response =>
    UserTest(
      (response.json \ "id").as[String],
      (response.json \ "login").as[String]
    )
}

futureResult.map(r => println(r.id, r.login))

Does somebody know why code into documentation doesn't work? What is wrong with it? Could I use my code?

One of parameters gets Null but it set as String. – Artem Seleznev Aug 09 '20 at 14:00 — Artem Seleznev, Aug 09 '20 at 14:00

score 2 · Accepted Answer · answered Aug 08 '20 at 15:22

2

Calling validate[User] doesn't return a User but a JsResult[User]. This is because the JSON data might be invalid and your code needs to handle this case. There is an example in the documentation that you have linked to:

json.validate[Place] match {
  case JsSuccess(place, _) => {
    val _: Place = place
    // do something with place
  }
  case e: JsError => {
    // error handling flow
  }
}

answered Aug 08 '20 at 15:22

Matthias Berndt

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So, I found mistake. My code didn't work because one of parameters got Null, due to your recommendation I found it. It turned out that you must set not only type but Null also – Artem Seleznev Aug 09 '20 at 13:59

How could I properly work with Scala Play Read?

1 Answers1