Supports deserialization of value class (inline class).

[k163377]

jackson-module-kotlin currently does not support deserialization of value class.
This issue summarizes information about deserialization support for value class.

About why jackson-module-kotlin has difficulty supporting value class.

The main reason it is difficult to support value class in jackson-module-kotlin is that the bytecodes for the value class and its associated arguments and return values are different than usual.
Jackson is a Java Reflection based library and cannot fully parse such content.
As far as I have tried in the experimental project described below, I have already found that full support is impractical unless an option is provided by Kotlin to ensure compatibility.

Implementation status of value class support.

value class support is being preliminarily implemented in the following experimental project.
At this time, I have confirmed that it works in many major cases, even for deserialization.
https://github.com/ProjectMapK/jackson-module-kogera

The implementation of this project will be incorporated into jackson-module-kotlin in the future.

The following issue also has information.
#199 (comment)

[k163377]

Support for JsonDeserialize and JacksonInject annotations for value class parameters has been confirmed from an experimental implementation in kogera.
https://github.com/ProjectMapK/jackson-module-kogera/releases/tag/2.16.0-beta8

As jackson-module-kotlin 2.17 allows updates to Kotlin 1.7 or later, I will try to introduce value class support.

[k163377]

cross-posting
#199 (comment)

[geirsagberg]

Deserializing a map where the key is a value class does not work in 2.17 unfortunately:

import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper

@JvmInline
value class Id(val value: Int)

data class Foo(val valuesById: Map<Id, String>)

val objectMapper = jacksonObjectMapper()

val serialized = objectMapper.writeValueAsString(Foo(mapOf(Id(1) to "one", Id(2) to "two")))

val deserialized = objectMapper.readValue(serialized, Foo::class.java)

Throws:

Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot find a (Map) Key deserializer for type...

[pschichtel]

@geirsagberg I guess this would be better reported in a dedicated issue

[geirsagberg]

Created an issue: #777