Play framework read from json list - json

Question

So I have a structure in json looking like this:
{
"lst": [
{"name": "foo"},
{"name": "bar"}
]
}
I'm having the hardest time converting this to a list of case classes. I'm sure I'm missing something completely obvious...
I have tried this:
case class Person(name: String)
implicit val personReads: Reads[Email] = (__ \\ "name").read[String](Person)
// endpoint
def person = Action { request =>
val person = request.body.asJson.get.as[Seq[Person]]
}
which doesn't compile since read doesn't return a FunctionBuilder which means I can't apply the path to Person
Adding a new parameter does compile (changing the json and case class accordingly):
case class Person(name: String, age: String)
implicit val personReads: Reads[Email] = (
(__ \\ "name").read[String]) and
(__ \\ "age").read[Int](Person)
but throws an exception Execution exception[[JsResultException: JsResultException(errors:List((,List(ValidationError(List(error.expected.jsarray),WrappedArray())))))]] supposedly because it expects a list.
So I tried adding this:
implicit val personsReads: Reads[Seq[Person]] = (__ \ "lst").read[Seq[Person]]
which then throws a NullPointer.
In the end I just want a Seq[Person].
Can anyone point me in the right direction, I'm completely lost to what I'm expected to do here...

Answer 1

You can do the following instead of giving reads and writes explicitly.
import play.api.json.Json
case class Person(name: String)
object Person {
implicit val personFormat = Json.format[Person]
}
case class Persons(lst: List[Person])
object Persons {
implicit val personsFormat = Json.format[Persons]
}
Now take the json string lets say jsonStr
Json.parse(jsonStr).validate[Persons] match {
case JsSuccess(persons, _) => println(persons)
case JsError(_) => println("parsing failed")
}
Scala REPL
scala> import play.api.libs.json._
import play.api.libs.json._
scala> val str = """{
| "lst": [
| {"name": "foo"},
| {"name": "bar"}
| ]
| }""".stripMargin
str: String =
{
"lst": [
{"name": "foo"},
{"name": "bar"}
]
}
scala> :paste
// Entering paste mode (ctrl-D to finish)
case class Person(name: String)
object Person {
implicit val personFormat = Json.format[Person]
}
case class Persons(lst: List[Person])
object Persons {
implicit val personsFormat = Json.format[Persons]
}
// Exiting paste mode, now interpreting.
defined class Person
defined object Person
defined class Persons
defined object Persons
scala> val jsonStr = str
jsonStr: String =
{
"lst": [
{"name": "foo"},
{"name": "bar"}
]
}
scala> :paste
// Entering paste mode (ctrl-D to finish)
Json.parse(jsonStr).validate[Persons] match {
case JsSuccess(persons, _) => println(persons)
case JsError(_) => println("parsing failed")
}
// Exiting paste mode, now interpreting.
Persons(List(Person(foo), Person(bar)))
Now when you change your Person case class and add age field.
case class Person(name: String, age: Int)
object Person {
implicit val personFormat = Json.format[Person]
}
Ensure that the json you are trying to parse contains both name and age. If you have only name then you will get parsing error.