@JsonValue not working for root

[iseki0]

Describe the bug

@JsonValue annotation on top node work correctly during serialization but fault on deserialization.

Version information

Latest

To Reproduce

val mapper = jacksonMapper()
data class A(@JsonValue val a: List<String>)
val s=mapper.writeValueAsString(A(listOf("A")) // OK: ["A"]
mapper.readValue(s,A::class.java) // boom!

Additional context

I use Kotlin.

[cowtowncoder]

I am not sure this is a bug as there is nothing automatic wrt @JsonValue on deserialization: it is not designed to have any effect on deserialization of POJOs... although Enums do have bit of special handling. Typically you'd need to use @JsonCreator with mode = JsonCreator.Mode.DELEGATING (NOT properties) to make deserialization work. So I think that's what is missing here.

But since this is Kotlin-specific, I will first move it to appropriate module.

[cowtowncoder]

Thinking about this a bit more, I realized that maybe @JsonValue on single constructor/factory method argument SHOULD imply "delegating" creator. And sent a question on jackson-dev list to see if others agree. This might, in future, allow usage like above (I am not 100% how Kotlin compiler associates annotations to know if it could "just" work). But I think this might be bit more readable than using @JsonCreator(mode = ).

[iseki0]

@cowtowncoder thank for your work.

[dinomite]

@cpdyj Expanding on the DELEGATING mode which is what I've used:

val mapper = jacksonObjectMapper()

data class A @JsonCreator(mode = JsonCreator.Mode.DELEGATING) constructor(@JsonValue val a: List<String>)

val s = mapper.writeValueAsString(A(listOf("A")))
mapper.readValue(s, A::class.java)

Automatically make it work with @JsonValue would be nice, though.