custom deserialization with absent Optional returns null

When using a custom deserialization for an Optional field, then the absence of that field is returning null instead of Optional.empty().

I reproduced with my own test method in the test class OptionalTest.java:

    public void testWithCustomDeserializerIfOptionalAbsent() throws Exception
    {
        assertEquals(Optional.empty(), MAPPER.readValue("{}",
                CaseChangingStringWrapper.class).value);

        assertEquals(Optional.empty(), MAPPER.readValue(aposToQuotes("{'value':null}"),
                CaseChangingStringWrapper.class).value);
    }

The first check fails, because of Jackson setting the value field to null.

[rkeytacked]

Finally I found the root cause of my misunderstanding. The deserialization was inconsistent amongst my POJOs.

I just realized that this is because of Lombok generating the @ConstructorProperties to the @AllArgsConstructor. Lombok does that even if the constructor is implicit by @Builder, and even if access level is set to PRIVATE explicitely.

Jackson calls this annotated constructor always with Optional.empty() values for all absent fields that are of type Optional. Even if the constructor is private. Hence my POJOs behave differently when defined with or without Lombok’s @AllArgsConstructor.

Similar issues have been discussed last year already, e.g. https://github.com/FasterXML/jackson-databind/issues/618 Not sure, if someone actually realized before that the different behavior for Optional fields comes from Lombok’s generated @ConstructorProperties.

[cowtowncoder]

Yes, there is special tracking for members coming via creators, since they must be buffered anyway (unlike field/setter assigned ones). There is also an issue (quite old) for trying to extend optional handling of missing values to all properties. Its implementation has not started, there is some hope it could be done with Jackson 3.x.

So I think it can be considered an implementation limitation at this point.

Will close.