Stop jackson-scala-module serializing all fields by default

Question

Using DefaultObjectMapper from jackson-scala-module, in the following examples, field is serialised in the Scala version, but not in the Java version. Setting com.fasterxml.jackson.databind.MapperFeature.AUTO_DETECT_FIELDS has no effect.

I wish for no fields to be serialised unless a field is annotated with com.fasterxml.jackson.annotation.JsonInclude.

Scala

class ScalaClass {
  val field = "someField"
}

Java

public class JavaClass {
  public String field = "someField";
}

Answer 1

Instead, disable MapperFeature.AUTO_DETECT_GETTERS and use @JsonGetter on a field.

This works for me:

import com.fasterxml.jackson.annotation.JsonGetter
import com.fasterxml.jackson.databind.{MapperFeature, ObjectMapper, SerializationFeature}
import com.fasterxml.jackson.module.scala.DefaultScalaModule

val mapper = new ObjectMapper()
mapper.registerModule(DefaultScalaModule)

mapper.disable(MapperFeature.AUTO_DETECT_GETTERS)
mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)

class ScalaClass {
  val field = "someField"
  @JsonGetter val includedField = "fieldValue"
}

mapper.writer().writeValueAsString(new ScalaClass) // => res: String = {"includedField":"fieldValue"}

The Java analogy to your Scala class is more likely to be:

public class JavaClass {
    public String getField() { return "someField"; }
}

UPDATE: Used @JsonGetter to include the field in serialization.