jackson-databind: Mix-ins do not work for `Enum`s

create java enum like this

public enum SomeEnum {
    none,
    tax10,
    tax20
}

create mixin for enum

public enum  SomeEnumMixin {
    @JsonProperty("zero")
    none,
    @JsonProperty("TypTyp")
    tax10,
    @JsonProperty("PytPyt")
    tax20
}

register mixin via .addMixIn(SomeEnum.class, SomeEnumMixin.class)
try to deserialize sometithing

ObjectMapper throws NullPointerException

java.lang.NullPointerException
	at com.fasterxml.jackson.databind.introspect.AnnotatedFieldCollector._addFieldMixIns(AnnotatedFieldCollector.java:117)
	at com.fasterxml.jackson.databind.introspect.AnnotatedFieldCollector._findFields(AnnotatedFieldCollector.java:94)
	at com.fasterxml.jackson.databind.introspect.AnnotatedFieldCollector.collect(AnnotatedFieldCollector.java:48)
	at com.fasterxml.jackson.databind.introspect.AnnotatedFieldCollector.collectFields(AnnotatedFieldCollector.java:43)
	at com.fasterxml.jackson.databind.introspect.AnnotatedClass._fields(AnnotatedClass.java:366)
	at com.fasterxml.jackson.databind.introspect.AnnotatedClass.fields(AnnotatedClass.java:338)
	at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector._addFields(POJOPropertiesCollector.java:393)
	at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector.collectAll(POJOPropertiesCollector.java:322)
	at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector.getPropertyMap(POJOPropertiesCollector.java:287)
	at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector.getProperties(POJOPropertiesCollector.java:186)
	at com.fasterxml.jackson.databind.introspect.BasicBeanDescription._properties(BasicBeanDescription.java:164)
	at com.fasterxml.jackson.databind.introspect.BasicBeanDescription.findProperties(BasicBeanDescription.java:239)
	at com.fasterxml.jackson.databind.deser.BasicDeserializerFactory._findCreatorsFromProperties(BasicDeserializerFactory.java:292)
	at com.fasterxml.jackson.databind.deser.BasicDeserializerFactory._constructDefaultValueInstantiator(BasicDeserializerFactory.java:276)
	at com.fasterxml.jackson.databind.deser.BasicDeserializerFactory.createEnumDeserializer(BasicDeserializerFactory.java:1472)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer2(DeserializerCache.java:371)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:349)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:264)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
	at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:142)
	at com.fasterxml.jackson.databind.DeserializationContext.findNonContextualValueDeserializer(DeserializationContext.java:481)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.resolve(BeanDeserializerBase.java:497)
	at com.fasterxml.jackson.databind.deser.std.DelegatingDeserializer.resolve(DelegatingDeserializer.java:58)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:293)
	at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
	at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:142)
	at com.fasterxml.jackson.databind.DeserializationContext.findRootValueDeserializer(DeserializationContext.java:491)
	at com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:4669)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4478)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3434)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3402)

I’ve tested on 2.11.0 and 2.11.1

About this issue

Original URL
State: closed
Created 4 years ago
Reactions: 1
Comments: 17 (15 by maintainers)

Commits related to this issue

Add a test for #2787, partial fix (no more NPE, now fails otherwise) — committed to FasterXML/jackson-databind by cowtowncoder 4 years ago
Minor refactoring wrt Enum resolver construction needed for #2787 — committed to FasterXML/jackson-databind by cowtowncoder a year ago
Improve JavaDoc wrt #2787 — committed to JooHyukKim/jackson-databind by JooHyukKim a year ago
Update release notes wrt #2787 — committed to FasterXML/jackson-databind by cowtowncoder a year ago
Minor post-merge clean up for #2787 — committed to FasterXML/jackson-databind by cowtowncoder a year ago

Most upvoted comments

It seems this issue can be closed now, addressed by #3990 ?

JooHyukKim on Nov 5, 2023

… correct, that’s t

I think someone else is tagged 😅here.

Sorry. Auto-completion for the win. 😕

cowtowncoder on Mar 24, 2023

@cowtowncoder thankssss for the mention! Like you thought, I did try tackling already 🤣.

That time I got caught up with other PR, but now that you mention it, I will go back to it now. Do you think below method would be the right place to start?

https://github.com/FasterXML/jackson-databind/blob/95f29d2818634be6e7a396d5d2cb1d9dcb12997e/src/main/java/com/fasterxml/jackson/databind/deser/BasicDeserializerFactory.java#L1664

And possibly somewhere in that method, do introspection like…

Class<?> mixInClass = ctxt.getConfig().findMixInClassFor(type.getRawClass());
JavaType mixInType = ctxt.constructType(mixInClass);

then pass in additional lookup for the construction of an EnumDeserializer?

JooHyukKim on Mar 14, 2023

Ah. The problem is that unlike POJO properties that are discovered using AnnotatedField / -Method and so on – on which mix-ins are applied – enum names are detected directly from fields that Enum declares, by JacksonAnnotationIntrospector. This means mix-ins are not indeed applied.

This should be fixed but will be bit bigger undertaking as it requires changes to AnnotationIntrospector interface, for one. That means it can not be fixed for versions earlier than 2.12.0.

cowtowncoder on Jul 11, 2020