Support nullable optionals and generic collections#921
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XN137
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Jul 20, 2026
| private JavaType elementType(JavaType type) { | ||
| JavaType elementType = type.getContentType(); | ||
| if (elementType == null && type.containedTypeCount() > 0) { | ||
| elementType = type.containedType(0); |
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just to confirm: even for Maps containedType(0) refers to the value type?
or do Maps always have a non-null getContentType ?
do we support raw maps without type parameters?
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Nice catch! containedType(0) would indeed be the key type for Map<K,V>.
Jackson map types always have a non-null getContentType() representing the value type, including raw maps, for which Jackson uses Object for both key and value.
So the fallback is not reached here and raw maps behave as before.
Still, using elementType() for maps is misleading, so I’ll switch that line back to type.getContentType().
Jackson property type inference only recognized List as a CEL list-like type and treated Optional as an object-like value. Runtime adaptation had the same List-only limitation and returned Optional values as ordinary objects. Generalize runtime list adaptation to Collection, unwrap Optional values to either their contained CEL value or null, and teach the Jackson 2 and Jackson 3 type descriptors to infer Collection<T> as list<T> and Optional<T> as T. Add regression coverage for Collection, Set, Optional.of, Optional.empty, and nested Optional values.
XN137
approved these changes
Jul 20, 2026
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Jackson property type inference only recognized List as a CEL list-like type and treated Optional as an object-like value. Runtime adaptation had the same List-only limitation and returned Optional values as ordinary objects.
Generalize runtime list adaptation to Collection, unwrap Optional values to either their contained CEL value or null, and teach the Jackson 2 and Jackson 3 type descriptors to infer Collection as list and Optional as T. Add regression coverage for Collection, Set, Optional.of, Optional.empty, and nested Optional values.