Create a json deserializer and use it - scala

Question

How do you create a jackson custom serializer and use it in your program? The serializer is used to serialize data from a kafka stream, because my job fails if it encounters a null.
I tried the following to create a serializer.
import org.json4s._
import org.json4s.jackson.JsonMethods._
case class Person(
val user: Option[String]
)
object PersonSerializer extends CustomSerializer[Person](formats => ( {
case JObject(JField("user", JString(user)) :: Nil) => Person(Some(user))
case JObject(JField("user", null) :: Nil) => Person(None)
},
{
case Person(Some(user)) => JObject(JField("user", JString(user)) :: Nil)
case Person(None) => JObject(JField("user", JString(null)) :: Nil)
}))
I am trying to use it this way.
object ConvertJsonTOASTDeSerializer extends App
{
case class Address(street : String, city : String)
case class PersonAddress(name : String, address : Address)
val testJson1 =
"""
{ "user": null,
"address": {
"street": "Bulevard",
"city": "Helsinki",
"country": {
"code": "CD" }
},
"children": [
{
"name": "Mary",
"age": 5,
"birthdate": "2004-09-04T18:06:22Z"
},
{
"name": "Mazy",
"age": 3
}
]
}
"""
implicit var formats : Formats = DefaultFormats + PersonSerializer
val output = parse(testJson1).as[Person]
println(output.user)
}
I am getting an error saying that
Error:(50, 35) No JSON deserializer found for type com.examples.json4s.Person. Try to implement an implicit Reader or JsonFormat for this type.
val output = parse(testJson1).as[Person]

Answer 1

Not sure if I answer your question. I provide the runnable code:
import org.json4s._
import org.json4s.jackson.JsonMethods._
case class Person(
user: Option[String],
address: Address,
children: List[Child]
)
case class Address(
street: String,
city: String,
country: Country
)
case class Country(
code: String
)
case class Child(
name: String,
age: Int
)
val s =
"""
{ "user": null,
"address": {
"street": "Bulevard",
"city": "Helsinki",
"country": {
"code": "CD" }
},
"children": [
{
"name": "Mary",
"age": 5,
"birthdate": "2004-09-04T18:06:22Z"
},
{
"name": "Mazy",
"age": 3
}
]
}
"""
implicit val formats : Formats = DefaultFormats
parse(s).extract[Person] // Person(None,Address(Bulevard,Helsinki,Country(CD)),List(Child(Mary,5), Child(Mazy,3)))