spray json in scala: deserializing json with unknown fields without losing them - json

Question

I'm looking for a solution to this but for json spray and my searches and attempts to get this working with json spray have failed thus far.
If I have the following json:
{
"personalData": {
"person": {
"first": "first_name",
"last": "last_name"
},
"contact": {
"phone": "1111111",
"address": {
"line": "123 Main St",
"city": "New York"
}
},
"xx": "yy", // unknown in advanced
"zz": { // unknown in advanced
"aa": "aa",
"bb": "bb",
"cc": {
"dd": "dd",
"ee": "ee"
}
}
}
}
We know for sure that the json will contain person and contact but we don't know what other fields may be created upstream from us that we don't care about/use.
I want to serialize this JSON into a case class containing person and contact but on the other hand, I don't want to lose the other fields (save them in a map so the class will be deserialized to the same json as received).
This is how far I've made it:
case class Address(
line: String,
city: String,
postalCode: Option[String]
)
case class Contact(
phone: String,
address: Address
)
case class Person(
first: String,
last: String
)
case class PersonalData(
person: Person,
contact: Contact,
extra: Map[String, JsValue]
)
implicit val personFormat = jsonFormat2(Person)
implicit val addressFormat = jsonFormat3(Address)
implicit val contactFormat = jsonFormat2(Contact)
implicit val personalDataFormat = new RootJsonFormat[PersonalData] {
def write(personalData: PersonalData): JsValue = {
JsObject(
"person" -> personalData.person.toJson,
"contact" -> personalData.contact.toJson,
// NOT SURE HOW TO REPRESENT extra input
)
}
def read(value: JsValue): CAERequestBEP = ???
}
Can someone help me do this with spray.json instead of play? I've spent such a long time trying to do this and can't seem to make it work.

Answer 1

In order to do that, you need to write your own formatter for PersonalDataFormat:
case class Person(first: String, last: String)
case class Address(line: String, city: String)
case class Contact(phone: String, address: Address)
case class PersonalData(person: Person, contact: Contact, extra: Map[String, JsValue])
case class Entity(personalData: PersonalData)
implicit val personFormat = jsonFormat2(Person)
implicit val addressFormat = jsonFormat2(Address)
implicit val contactFormat = jsonFormat2(Contact)
implicit object PersonalDataFormat extends RootJsonFormat[PersonalData] {
override def read(json: JsValue): PersonalData = {
val fields = json.asJsObject.fields
val person = fields.get("person").map(_.convertTo[Person]).getOrElse(???) // Do error handling instead of ???
val contact = fields.get("contact").map(_.convertTo[Contact]).getOrElse(???) // Do error handling instead of ???
PersonalData(person, contact, fields - "person" - "contact")
}
override def write(personalData: PersonalData): JsValue = {
JsObject(personalData.extra ++ ("person" -> personalData.person.toJson, "contact" -> personalData.contact.toJson))
}
}
implicit val entityFormat = jsonFormat1(Entity)
val jsonResult = jsonString.parseJson.convertTo[Entity]
The result is:
Entity(PersonalData(Person(first_name,last_name),Contact(1111111,Address(123 Main St,New York)),Map(xx -> "yy", zz -> {"aa":"aa","bb":"bb","cc":{}})))
(Assuming the json is not exactly the json above, but a valid similar one)
Code run in Scastie