#JsonIgnore serialising Scala case class property using Jackon and Json4s - scala

Question

I'm trying to prevent one of the properties of a Scala case class being serialised. I've tried annotating the property in question with the usual #JsonIgnore and I've also tried attaching the #JsonIgnoreProperties(Array("property_name")) to the case class. Neither of which seem to achieve what I want.
Here's a small example:
import org.json4s._
import org.json4s.jackson._
import org.json4s.jackson.Serialization
import org.json4s.jackson.Serialization.{read, write}
import com.fasterxml.jackson.annotation._
object Example extends App {
#JsonIgnoreProperties(Array("b"))
case class Message(a: String, #JsonIgnore b: String)
implicit val formats = Serialization.formats(NoTypeHints)
val jsonInput = """{ "a": "Hello", "b":"World!" }"""
val message = read[Message](jsonInput)
println("Read " + message) // "Read Message(Hello,World!)
val output = write(message)
println("Wrote " + output) // "Wrote {"a":"Hello","b":"World!"}"
}

Answer 1

Change your #JsonIgnore to #JsonProperty("b"). You have correctly stated to Ignore the property 'b but 'b has not yet been annotated as a property.
#JsonIgnoreProperties(Array("b"))
case class Message(a: String, #JsonProperty("b") b: String)

Answer 2

With jackson-databind 2.8.6 and jackson-module-scala 2.8.4
"com.fasterxml.jackson.core" % "jackson-databind" % "2.8.6",
"com.fasterxml.jackson.module" % "jackson-module-scala_2.11" % "2.8.4"
Only #JsonIgnoreProperties works fine,
Example case class as below where I'm ignoring "eventOffset" and "hashValue",
import java.util.Date
import com.fasterxml.jackson.annotation.{JsonIgnore, JsonIgnoreProperties}
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule
import com.fasterxml.jackson.module.scala.experimental.ScalaObjectMapper
#JsonIgnoreProperties(Array("eventOffset", "hashValue"))
case class TestHappenedEvent(eventOffset: Long, hashValue: Long, eventType: String,
createdDate: Date, testField: String) {
def this() {
this(0, 0, "", new Date(), "")
}
def toJSON(): String = {
val objectMapper = new ObjectMapper() with ScalaObjectMapper
objectMapper.registerModule(DefaultScalaModule)
val data = this.copy()
val stream = new ByteArrayOutputStream()
objectMapper.writeValue(stream, data)
stream.toString
}
}
test
import org.scalatest.FunSuite
import spray.json._
class BaseEventSpecs extends FunSuite {
val abstractEvent = TestHappenedEvent(0, 1, "TestHappenedEvent", new Date(2017, 10, 28), "item is sold")
test("converts itself to JSON") {
assert(abstractEvent.toJSON().parseJson ==
"""
{
"eventType":"TestHappenedEvent",
"createdDate":61470000000000,
"testField":"item is sold"
}
""".stripMargin.parseJson)
}
}