converting multiple json objects into scala objects - json

Question

How do I read multiple json objects from a request and convert them into my own custom object. For example, lets say we are retrieving a list of users with the following json:
{
"users":[
{
"name": "Bob",
"age": 31.0,
"email": "bob#gmail.com"
},
{
"name": "Kiki",
"age": 25.0,
"email": null
}
]
}
and my case class looks like the following
case class User(firstName: String, age: Double, email: String)
In this case the firstName value is differnt from the "name" json value. How do I get a Seq[User] from the given json file with the different names. I can't find any examples where someone is reading from a json file with multiple objects.
Thanks in advance.

Answer 1

Play's type class-based JSON library provides reader and writer instances for Seq[A] for any A with the appropriate instances, so all you have to do is provide a reader instance for your user type and you get a reader for a collection of users for free.
We can start with the following case class (note that I've made the fact that the email address is optional explicit with Option):
case class User(firstName: String, age: Double, email: Option[String])
Next we define our reader. I'm using 2.1's combinators, but there are other (more verbose) options.
import play.api.libs.json._
import play.api.libs.functional.syntax._
implicit val userReads = (
(__ \ 'name).read[String] and
(__ \ 'age).read[Double] and
(__ \ 'email).read[Option[String]]
)(User.apply _)
We can test it:
val userJson = """{
"users": [
{ "name": "Bob", "age": 31.0, "email": "bob#gmail.com" },
{ "name": "Kiki", "age": 25.0, "email": null }
]
}"""
val users = (Json.parse(userJson) \ "users").as[Seq[User]]
And then:
scala> users foreach println
User(Bob,31.0,Some(bob#gmail.com))
User(Kiki,25.0,None)
As expected.