com.fasterxml.jackson.annotation.Nulls#SKIP源码实例Demo

@Override
public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
        BeanProperty property) throws JsonMappingException
{
    Boolean unwrapSingle = findFormatFeature(ctxt, property, _valueClass,
            JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
    NullValueProvider nuller = null;

    Nulls nullStyle = findContentNullStyle(ctxt, property);
    if (nullStyle == Nulls.SKIP) {
        nuller = NullsConstantProvider.skipper();
    } else if (nullStyle == Nulls.FAIL) {
        if (property == null) {
            nuller = NullsFailProvider.constructForRootValue(ctxt.constructType(_valueClass));
        } else {
            nuller = NullsFailProvider.constructForProperty(property);
        }
    }
    if ((unwrapSingle == _unwrapSingle) && (nuller == _nuller)) {
        return this;
    }
    return withResolved(nuller, unwrapSingle);
}
 

/**
 * Method called to find {@link NullValueProvider} for a contents of a structured
 * primary property (Collection, Map, array), using
 * "content nulls" setting. If no provider found (not defined),
 * will return given value deserializer (which is a null value provider itself).
 *
 * @since 2.9
 */
protected NullValueProvider findContentNullProvider(DeserializationContext ctxt,
        BeanProperty prop, JsonDeserializer<?> valueDeser)
    throws JsonMappingException
{
    final Nulls nulls = findContentNullStyle(ctxt, prop);
    if (nulls == Nulls.SKIP) {
        return NullsConstantProvider.skipper();
    }
    NullValueProvider prov = _findNullProvider(ctxt, prop, nulls, valueDeser);
    if (prov != null) {
        return prov;
    }
    return valueDeser;
}
 

protected final NullValueProvider _findNullProvider(DeserializationContext ctxt,
        BeanProperty prop, Nulls nulls, JsonDeserializer<?> valueDeser)
    throws JsonMappingException
{
    if (nulls == Nulls.FAIL) {
        if (prop == null) {
            return NullsFailProvider.constructForRootValue(ctxt.constructType(valueDeser.handledType()));
        }
        return NullsFailProvider.constructForProperty(prop);
    }
    if (nulls == Nulls.AS_EMPTY) {
        // cannot deal with empty values if there is no value deserializer that
        // can indicate what "empty value" is:
        if (valueDeser == null) {
            return null;
        }

        // Let's first do some sanity checking...
        // NOTE: although we could use `ValueInstantiator.Gettable` in general,
        // let's not since that would prevent being able to use custom impls:
        if (valueDeser instanceof BeanDeserializerBase) {
            ValueInstantiator vi = ((BeanDeserializerBase) valueDeser).getValueInstantiator();
            if (!vi.canCreateUsingDefault()) {
                final JavaType type = prop.getType();
                ctxt.reportBadDefinition(type,
                        String.format("Cannot create empty instance of %s, no default Creator", type));
            }
        }
        // Second: can with pre-fetch value?
        {
            AccessPattern access = valueDeser.getEmptyAccessPattern();
            if (access == AccessPattern.ALWAYS_NULL) {
                return NullsConstantProvider.nuller();
            }
            if (access == AccessPattern.CONSTANT) {
                return NullsConstantProvider.forValue(valueDeser.getEmptyValue(ctxt));
            }
        }
        return new NullsAsEmptyProvider(valueDeser);
    }
    if (nulls == Nulls.SKIP) {
        return NullsConstantProvider.skipper();
    }
    return null;
}
 

@JsonSetter(nulls=Nulls.SKIP)
public void setNoNulls(String v) {
    _noNulls = v;
}