hello 👋 has anyone tried

value class

with jackson?

fun main() {
  val string = ObjectMapper().findAndRegisterModules()
    .convertValue<Map<String, String>>(Value("any"))

  println(string)
}

@JvmInline
value class Value(val value: String)

prints

{value=any}

with jackson 2.12.5, but fails with jackson 2.13.0. error is

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('any')
 at [Source: UNKNOWN; byte offset: #UNKNOWN]

though https://github.com/FasterXML/jackson-module-kotlin/issues/464 makes me wonder if my expectation is wrong. my use case is the one marked as “broken”:

"broken": [ {"value":0}, {"value":0} ]

, though this is exactly what I want

The policy is to serialize the

value class

with an

unboxed

value in any case. Custom serializers configured for

value class

do not currently work for this use case. https://github.com/FasterXML/jackson-module-kotlin/issues/524 An attempt to make this work properly is underway in the following PR https://github.com/FasterXML/jackson-module-kotlin/pull/527 When this PR is merged, I believe it will be possible to make it work as expected by using a custom serializer. Also, if there is a strong desire to serialize the`toString` form as well as the

data class

, an additional option may be introduced in the

KotlinModule

. You can also open an issue on GitHub about this option.