`Optional<Boolean>` is not recognized as boolean field

[thnaeff]

A method like this

  public Optional<Boolean> isUsed() {
    return Optional.ofNullable(used);
  }

does not seem to get automatically recognized by Jackson as a field to include for serialization, meaning that it does not appear in the serialized JSON at all.

Changing it to this works since it is now a standard boolean return type

  public Boolean isUsed() {
    return used;
  }

What also works is annotating it. However, this then produces a field isUsed (it does not strip the is as it generally happens for boolean properties). Annotating a Optional<String> get... method with @JsonProperty works as expected with stripping the get.

  @JsonProperty
  public Optional<Boolean> isUsed() {
    return Optional.ofNullable(used);
  }

So to get the "standard" boolean field behavior it needs

  @JsonProperty("used")
  public Optional<Boolean> isUsed() {
    return Optional.ofNullable(used);
  }

Any get methods are recognized by default, so I would think this is an issue specific to boolean properties.

I should note that this has been run with jackson-datatype-jdk8/-annotations/-core v2.13.3 as well as v2.15.0-rc1, both with same behavior

[cowtowncoder]

Hmmh. Yes, I can see this occurring. And I can see why is non-intuitive.

The challenge is that of core databind recognizing structure type that it does not directly support. This might be possible to recognize given Optional is a ReferenceType, although it's hard to say before trying to make it work.

[cowtowncoder]

Although this is correctly filed here wrt initial symptom, the fix (if any) needs to go in jackson-databind so I will transfer the issue there. It can be verified with AtomicReference<Boolean> which behaves similar to Optional<Boolean> and is directly supported by jackson-databind itself.

[cowtowncoder]

Ok so the location for the fix is method findNameForIsGetter() in DefaultAccessorNamingStrategy:

        if (_isGetterPrefix != null) {
            final Class<?> rt = am.getRawType();
            if (_isGettersNonBoolean || rt == Boolean.class || rt == Boolean.TYPE) {
                if (name.startsWith(_isGetterPrefix)) {
                    return _stdBeanNaming
                            ? stdManglePropertyName(name, 2)
                            : legacyManglePropertyName(name, 2);
                }
            }
        }

where we need to change things a bit. But it seems pretty much doable.

[cowtowncoder]

Fixed, tested with AtomicBoolean and AtomicReference<Boolean> -- should work for Optional<Boolean> too.

Actually will verify in master.