feat: Infer discriminator mapping #4983
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PatrickFeiring
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Oct 4, 2025
| } else { | ||
| SerializationConfig config = _mapper.getSerializationConfig(); | ||
| AnnotationIntrospector introspector = config.getAnnotationIntrospector(); | ||
| List<NamedType> subTypes = introspector.findSubtypes( |
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As outlined in the issue comment, there are likely ways to find subtypes in a more exhaustive manner, but using the introspector seemed a good conservative starting point that covers the most common use-cases, as I don't know Jackson internals all that well
#3411 (comment)
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Description
This PR adds inference of discriminator mappings when an explicit mapping is not present.
It should greatly reduce the need for explicit
@DiscriminatorMappingannotations and make it easier to keep the mapping in sync.The basic theme of the approach is to leave as much resolving to Jackson as possible. This is done by instantiating a type serializer for the class, and let Jackson compute the ids used in the mapping. This means that both explicitly listed names in
@JsonSubTypes.Typeannotations works, as well as ids that Jackson compute using the mechanism listed inJsonTypeInfo.Id.Mappings are computed not only for sub types listed explicitly in
JsonSubTypesannotations, but should also for modules that customize theAnnotationInstrospectorsfindSubtypesmethod, such as https://github.com/sigpwned/jackson-modules-java-17-sealed-classes.Closes: #3411
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