Error in json serialization in Scala with Play2 - json

Question

i have following three case classes
case class Delete(var deleteStatus : DeleteStatus , var deleteReason : DeleteReason) // DeleteStatus and DeleteReason are enums
case class Message(val uuid: Int ,val subject : String, val body : String, var awt : Int,val dateTime : LocalDateTime = LocalDateTime.now(), delete : Delete)
case class Inbox( val uuid : Int,var messageList : ListBuffer[Message] )
i want to serialize them to Json and but i am not sure how should i do this
i have tried it like this
def writedelete(delete: Delete) = Json.obj(
"deleteStatus" -> delete.getDeleteStatusInt.toString,
"deleteReason" -> delete.getDeleteReasonInt.toString
)
def writeMessage(mgs : Message)= Json.obj(
"uuid" -> mgs.getUuid ,
"subject" -> mgs.getSubject,
"body" -> mgs.getBody,
"awt" -> mgs.getAwt,
"datetime" -> mgs.getdateTime.toString,
"delete" -> mgs.delete
)
def writeInbox(inbox : Inbox)= Json.obj(
"uuid" -> inbox.getUuid,
"mgslist" -> Seq(inbox.getMessageList)
)
but it gives following error on mgs.delete in writeMessage and mgslist in writeInbox
type mismatch; found : models.UserNotifications.MailMessages.Delete
required: play.api.libs.json.Json.JsValueWrapper
type mismatch; found :
Seq[scala.collection.mutable.ListBuffer[models.UserNotifications.MailMessages.Message]]
required: play.api.libs.json.Json.JsValueWrapper
please guide me how can i get get rid off it
and also is there any better way of doing this?

Answer 1

When you use Json.obj(...) to construct a JSON object various implicit conversions are available to convert common types (e.g. String, Int) to their JSON wrapper types (JsString, JsNumber). The problem with your code is there are no implicit conversions available to convert your Delete and Message types to JSON. One option would be to use your explicit conversion functions directly, e.g:
"delete" -> writeDelete(mgs.delete)
and (using Json.arr(...) to construct a JSON array):
"msglist" -> Json.arr(inbox.getMessageList.toSeq.map(writeMessage): _*)
However, the more idiomatic way to do this would be to use the JSON Inception macros to automatically generate (implicit) serializers for your types.
Simplifying slightly, this would look something like this:
case class Delete(deleteStatus: DeleteStatus, deleteReason: DeleteReason)
object Delete {
implicit val _format = Json.format[Delete]
}
case class Message(uuid: Int, subject: String, body: String, awt: Int, dateTime: LocalDateTime, delete: Delete)
object Message {
implicit val _format = Json.format[Message]
}
case class Inbox(uuid: Int, messageList: ListBuffer[Message])
object Inbox {
implicit val _format = Json.format[Message]
}
You should now be able to automatically serialize (and de-serialize) your Delete, Message, and Inbox objects using Json.toJson(thing) because it will find an implicit Format object (a combined Reads and Writes) on the companion object of each custom type.
One complication here is that your case classes contain enums; if they're Scala enumerations see this answer for how to convert them. I leave that as an exercise for the reader.