Case classes with option types don't follow serialization configuration

[fehguy]

I'm trying to keep jackson from writing the None Option value as "null". I believe the scala module is not honoring the serialization conf. In the following test case, the first two tests fail because they are returning {"foo":null} despite the mapper being configured to include only non-null values. The third is not a case class and passes with the expected response of "{}":

class ScalaOptionTest extends FlatSpec with ShouldMatchers {
  it should "not write a null value" in {
    val o = CaseClass1(None)
    getMapper.writeValueAsString(o) should be ("{}")
  }

  it should "not also write a null value" in {
    val o = CaseClass2(None)
    getMapper.writeValueAsString(o) should be ("{}")
  }

  it should "not still write a null value" in {
    val o = new TestObject3
    getMapper.writeValueAsString(o) should be ("{}")
  }

  def getMapper = {
    val mapper = new ObjectMapper()
    mapper.registerModule(new DefaultScalaModule())
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
    mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL)
    mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY)
  }
}

case class CaseClass1(@JsonInclude(JsonInclude.Include.NON_NULL) foo: Option[String])

case class CaseClass2(foo: Option[String])

class TestObject3() {
  var foo: Option[String] = None
}

which returns:

Tests in error: 
  should not write a null value(ScalaOptionTest): "{"foo":null}" was not equal to "{}"
  should not also write a null value(ScalaOptionTest): "{"foo":null}" was not equal to "{}"

[christophercurrie]

Thanks for the bug report, I'll take a look at why the works for normal classes and see what needs to be added to the case class logic.

[christophercurrie]

While I haven't yet worked out a way to support this using JsonInclude.Include.NON_NULL (which makes the most logical sense, but doesn't appear to have a hook in JsonSerializer, I have added support in OptionSerializer to recognize and honor JsonInclude.Include.NON_EMPTY to achieve the same goal.

[christophercurrie]

Reopening, as I realize now that this issue is slightly different than #9.

[christophercurrie]

I added what I think is a functionally equivalent pair of tests to CaseClassSerializerTest and was not able to reproduce the problem. If you can, please retest your use case with the latest code and reopen if you continue to have issues.

[christophercurrie]

Well it looks like my tests were bad. Reopening as I've fixed the tests and the problem still exists.

[christophercurrie]

Ok, filing in some more information so I don't forget it.

• The non-case class isn't succeeding because it's working properly, it's succeeding because the Scala module doesn't currently recognized the property. If I add @JsonProperty annotation to TestObject3, the test fails.
• Getting NOT_NULL recognized requires that Jackson recognize that it's possible for a non-null value in the JVM to be serialized as JSON "null". Jackson doesn't currently have a hook for this, but I've got an idea for an approach that might work by replacing BeanPropertyWriter with a new version that recognizes "null-like" values.

I should have a fix for this shortly.

[leons727]

With jackson 2.1.0 and jackson-module-scala 2.1.1-SNAPSHOT:

case class Foo(val a: String, val b: Option[Int] = None)

@RunWith(classOf[BlockJUnit4ClassRunner])
class TryJSON {

@test
def testNulls() {
val m = new ObjectMapper()
m.registerModule(new DefaultScalaModule())
m.setSerializationInclusion(JsonInclude.Include.NON_NULL)
println(m.writeValueAsString(new Foo(null, None)))
}
}

Prints:

{"a":null,"b":null}

Am I missing something?

[christophercurrie]

Nope, my tests are bad, #45 also reported this. Will fix ASAP and issue a 2.1.1 for it.

[christophercurrie]

This issue should be resolved in 2.1.1, just released.

[leons727]

Yes, works for me correctly now. Thanks for the quick turnaround!

[jsw]

This seems to be broken again in 2.7.4 and 2.7.5.

I setup my ObjectMapper using

val mapper = new ObjectMapper with ScalaObjectMapper
mapper.registerModule(DefaultScalaModule)
mapper.registerModule(new JavaTimeModule)
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL)
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
mapper.configure(DeserializationFeature.READ_DATE_TIMESTAMPS_AS_NANOSECONDS, false)

and the following test fails

val json = mapper.writeValueAsString(C(None, None))
assert(json === "{}")

[info] - should not serialize null fields *** FAILED ***
[info]   "{["a":null,"b":null]}" did not equal "{[]}" (JacksonUtilTest.scala:27)

[devshorts]

Seems still broken in 2.8.3 as well

[ptagr]

is there a workaround for this ?

[jsw]

Use JsonInclude.Include.NON_ABSENT. See issue 280