I'm working with Play JSON API (latest version; Play 2.4), reading incoming JSON into objects.
When writing JSON, there's absolutely no problem in using a list of custom objects, as long as I have implicit val writes = Json.writes[CustomType].
But apparently the inverse is not true, as the following does not work even though Reads is generated for both top-level type and list item type (using Json.reads[Incoming] and Json.reads[Item]). Is custom Reads implementation mandatory? Or am I missing something obvious? What is the simplest way to make this work?
Simplified example:
JSON:
{
"test": "...",
"items": [
{ "id": 44, "time": "2015-11-20T11:04:03.544" },
{ "id": 45, "time": "2015-11-20T11:10:10.101" }
]
}
Models/DTOs matching the incoming data:
import play.api.libs.json.Json
case class Incoming(test: String, items: List[Item])
object Incoming {
implicit val reads = Json.reads[Incoming]
}
case class Item(id: Long, time: String)
object Item {
implicit val reads = Json.reads[Item]
}
Controller:
def test() = Action(parse.json) { request =>
request.body.validate[Incoming].map(incoming => {
// ... handle valid incoming data ...
}).getOrElse(BadRequest)
}
Compiler has this to say:
No implicit format for List[models.Item] available.
[error] implicit val reads = Json.reads[Incoming]
^
No Json deserializer found for type models.Incoming.
Try to implement an implicit Reads or Format for this type.
[error] request.body.validate[Incoming].map(incoming => {
