Is there a way to skip null values for properties handled by @JsonAnySetter?

[pjfanning]

Discussed in #6169

^{Originally posted by margarita-sk August 20, 2026}
When configuring JsonMapper with null handling:

        .changeDefaultNullHandling(v -> v.withValueNulls(Nulls.SKIP))
        .changeDefaultNullHandling(v -> v.withContentNulls(Nulls.SKIP))

the configuration appears to have no effect on properties handled by @JsonAnySetter.

Reproduction

class Jackson3Test {

    @Test
    void testSkipNullValuesInJsonAnySetter() {
        JsonMapper jsonMapper = JsonMapper.builder()
                .changeDefaultNullHandling(v -> v.withValueNulls(Nulls.SKIP))
                .changeDefaultNullHandling(v -> v.withContentNulls(Nulls.SKIP))
                .build();

        String json = """
                {
                "non_null_property": "test",
                "null_property": null
                }
                """;
        TestPojo input = jsonMapper.readValue(json, TestPojo.class);

        Assertions.assertEquals(1, input.getDynamicProperties()
                .size()); // is failed, but expected to pass because of the default null handling configuration
    }
    
    static class TestPojo {

        private final Map<String, JsonNode> dynamicProperties = new HashMap<>();

        @JsonAnySetter
        public void setDynamicProperties(String key, JsonNode value) {
            this.dynamicProperties.put(key, value);
        }

        public Map<String, JsonNode> getDynamicProperties() {
            return this.dynamicProperties;
        }

    }

}

Actual behavior

The @JsonAnySetter method is invoked for both properties, including the property whose value is null.

Expected behavior

With the mapper configured with:

        .changeDefaultNullHandling(v -> v.withValueNulls(Nulls.SKIP))
        .changeDefaultNullHandling(v -> v.withContentNulls(Nulls.SKIP))

I would expect the null_property value to be skipped and the @JsonAnySetter method not to be invoked for it.

Question

Is the current behavior intentional for @JsonAnySetter?
If this is intentional, is there currently a recommended way to configure @JsonAnySetter to skip null values?
If it is not intentional, is support for applying Nulls.SKIP to @JsonAnySetter planned for Jackson 3?

[Dongnyoung]

I traced the deserialization paths for regular properties and @JsonAnySetter.

For regular bean properties, mapper-level default null handling is merged into property metadata during property construction/introspection. Later, during BeanDeserializerBase resolution, Nulls.SKIP is resolved via findValueNullProvider() to a skipping NullValueProvider, so VALUE_NULL causes the property setter to be skipped.

@JsonAnySetter appears to take a different path. In BeanDeserializerFactory.constructAnySetter(), the synthetic BeanProperty used by SettableAnyProperty is created with PropertyMetadata.STD_OPTIONAL, and I could not find an equivalent step that merges mapper-level default null handling into that metadata. Then SettableAnyProperty.deserialize() handles VALUE_NULL by calling the value deserializer’s getNullValue() and passes that value to the any-setter.

So this looks like mapper-level valueNulls(Nulls.SKIP) is not being propagated to SettableAnyProperty, rather than an intentional difference. I also could not find Javadoc or tests indicating that @JsonAnySetter is supposed to ignore default null handling.

For the example above, I think valueNulls(Nulls.SKIP) is the relevant setting. contentNulls should not be necessary for the method-based @JsonAnySetter case, since the incoming unknown property value itself is null.

If this is considered a bug, I’d be happy to work on a fix and add a regression test, while preserving the existing behavior where a custom value deserializer’s getNullValue() is honored for any-setter values.

[pjfanning]

@Dongnyoung I think this is likely to be a bug so if you have time to look at it, that would be great.