No way to explicitly disable wrapping in custom annotation processor

[SimonCockx]

When upgrading from Jackson 2.15.0 to 2.17.1, we noticed our custom annotation processor stopped working due to a change in behaviour in the way PropertyNames are merged. See #4364. I would like to know whether this is intended, and if it is, how I should migrate my code.

We have a custom XML annotation introspector which explicitly sets the wrapper name to Property.NO_NAME if our custom annotation is present and the type is a list:

    @Override
    public PropertyName findWrapperName(Annotated ann) {
        if (ann.hasAnnotation(RosettaAttribute.class) && hasCollectionType(ann)) {
            // Disable wrapping of lists.
            return PropertyName.NO_NAME;
        }
        return super.findWrapperName(ann);
    }

This used to work in Jackson 2.15.

Unfortunately, due to the change in #4364, PropertyName.NO_NAME is now merged with PropertyName.DEFAULT from the default Jackson XML annotation introspector, and the new behaviour prefers PropertyName.DEFAULT over PropertyName.NO_NAME. The previous behaviour would prefer PropertyName.NO_NAME.

I have not found a way to fix this. Is there a way to get rid of the default annotation processor?

Originally posted by @SimonCockx in #4364 (comment)

[cowtowncoder]

Ok, first work-arounds possible...

Logic change is in AnnotationIntrospectorPair, which is used when more than one introspector is to be used. To avoid its use, and merging logic, you might be able to sub-class default AnnotationIntrospector (for plain JSON it'd be JacksonAnnotationIntrospector, but for XML JacksonXmlAnnotationIntrospector), instead of registering your own.

If you do need to combine dynamically multiple AnnotationIntrospectors, it'd be possible to sub-class AnnotationIntrospectorPair but that might get complicated.
Actual merging logic is defined in PropertyName.merg(...)

[cowtowncoder]

But so, on possible actual fix. I think PropertyName.merge(...) needs to consider 2 special instances (NO_NAME and USE_DEFAULT) and return as-is, if primary value is either one.

I could make this change, although bit hesitant to do in 2.17(.2), instead of 2.18.

But one thing that I think I would need is a test case -- could you create a unit test to show the problem? It would need to go in jackson-dataformat-xml, but I can take care of that part.

In the meantime, I'll create a PR to show what might work.

[cowtowncoder]

Actually, I think only NO_NAME should have such special semantics.

Also, there is also the question of proper placement; in some ways, check in AnnotationIntrospectorPair would seem better, avoiding calls to secondary introspector.
But I think I will start with more universal solution of PropertyName.merge() checking (alternative can be added later on if need be).

[cowtowncoder]

Created #4596 (against 2.17) with proposed fix.

[SimonCockx]

Thanks for the quick resolution! Is there an ETA for the release by any chance?

To avoid its use, and merging logic, you might be able to sub-class default AnnotationIntrospector (for plain JSON it'd be JacksonAnnotationIntrospector, but for XML JacksonXmlAnnotationIntrospector), instead of registering your own.

How do I register my custom subclass of the default introspector? While I really have dug into the code, I have not found a way to "replace" the default, rather than registering a new one.

But one thing that I think I would need is a test case -- could you create a unit test to show the problem? It would need to go in jackson-dataformat-xml, but I can take care of that part.

Created a test here: FasterXML/jackson-dataformat-xml#659

[cowtowncoder]

On Mon, Jun 24, 2024 at 1:37 AM SimonCockx ***@***.***> wrote: Thanks for the quick resolution! Is there an ETA for the release by any chance? To avoid its use, and merging logic, you might be able to sub-class default AnnotationIntrospector (for plain JSON it'd be JacksonAnnotationIntrospector, but for XML JacksonXmlAnnotationIntrospector), instead of registering your own. How do I register my custom subclass of the default introspector? While I really have dug into the code, I have not found a way to

"replace" the default, rather than registering a new one.

ObjectMapper (and sub-classes) has something like "setAnnotationIntrospector()", and I think "XmlMapper.builder()" probably "annotationIntrospector(introspector)"

But one thing that I think I would need is a test case -- could you create a unit test to show the problem? It would need to go in jackson-dataformat-xml, but I can take care of that part. Created a test here: FasterXML/jackson-dataformat-xml#659 <FasterXML/jackson-dataformat-xml#659>

Thank you! -+ Tatu +-

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