Jackson fails to deserialize 1 field POJO

[WojciechDolata]

Describe the bug
When trying to deserialize JSON to POJO it fails when POJO has only one field.

Version information
2.11.4

To Reproduce
POJO:
@AllArgsConstructor //lombok, if i add constructor manually it still fails
public class SubjectRequest {
public final String name;
}

While trying to create this POJO via spring's @requestbody it fails. When i add another parameter, ex public final String a;
jackson works correctly. (creates POJO with {name: 'text', a: null})

Expected behavior
Jackson should be able to deserialize 1 field POJO

Error message

Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of ad.school.planner.inner.subject.SubjectRequest (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of ad.school.planner.inner.subject.SubjectRequest (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (PushbackInputStream); line: 2, column: 5]]

[cowtowncoder]

This is a well-known issue due to ambiguity of the 1-arg constructor case: single-argument could match either:

1. Delegating case like "string-value" OR
2. Properties-based case like {"name" : "value"}

and if user does not specify mode with

@JsonCreator(mode = JsonCreator.Mode.PROPERTIES) // or Mode.DELEGATING

Jackson will try to guess which one to use. In your case it likely guesses that DELEGATING mode is to be used and expects a String, not Object value.

I think Lombok has a way to get appropriate @JsonCreator (or @ContructorProperties which also implies properties-based approach).

Or... Jackson 2.12 does allow configuration to default to Properties, always. This is probably the best way:

https://cowtowncoder.medium.com/jackson-2-12-most-wanted-3-5-246624e2d3d0

[WojciechDolata]

Thanks a lot! Adding @JsonCreator(mode = JsonCreator.Mode.PROPERTIES) solved my issue.