Serialization and Deserialization of Kotlin data class fails on PolymorphicTypeValidator with Any

[effx13]

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Describe the bug

When trying to deserialize class that contains kotlin value class, Jackson throws InvalidTypeIdException with missing type id property '@class' on ObjectMapper.DefaultTyping.NON_FINAL
Despite adding @JsonCreator annotation, I got the same result.

And trying to serialize above class with ObjectMapper.DefaultTyping.NON_FINAL, Jackson throws JsonMappingException with class ServerName cannot be cast to class java.lang.String (ServerName is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap') (through reference chain: TestDto["serverName"])

I'm using PolymorphicTypeValidator and Any class to do serialization and deserialization in Redis. But no matter what settings and annotations I use, the serialization and deserialization fails.

Version Information

JVM 21
Kotlin 1.8

jackson-core:2.17.2
jackson-databind:2.17.2
jackson-annotations:2.17.2
jackson-datatype-jsr310:2.17.2
jackson-module-kotlin:2.17.2

Reproduction

@JvmInline
value class ServerName(
  val value: String,
) {
  companion object {
    @JsonCreator
    @JvmStatic
    fun fromValue(value: String): ServerName {
      return ServerName(value)
    }
  }
}

data class TestDto(
  val id: Int,
  val serverName: ServerName
)

val objectMapper = ObjectMapper()
  .registerKotlinModule()
  .registerModule(JavaTimeModule())
  .activateDefaultTyping(
    BasicPolymorphicTypeValidator.builder().allowIfBaseType(Any::class.java).build(),
    ObjectMapper.DefaultTyping.NON_FINAL, // or EVERYTHING
    JsonTypeInfo.As.PROPERTY,
  )

// on NON_FINAL
fun main() {
  val serverName = ServerName("TEST")
  val testDto = TestDto(1, serverName)

  val serialized = objectMapper.writeValueAsBytes(testDto)
  println(String(serialized))
  // Expected output: {"id":1,"serverName":"TEST"}
  // Actual output: {"id":1,"serverName":{"value":"TEST"}}

  val deserialized = objectMapper.readValue(serialized, Any::class.java) // Because of RedisSerializer
  println(deserialized)
  // Expected output: TestDto(id=1, serverName=ServerName(value=TEST))
  // Actual output: Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Could not resolve subtype of [simple type, class java.lang.Object]: missing type id property '@class'
}

// on EVERYTHING
fun main() {
  val serverName = ServerName("TEST")
  val testDto = TestDto(1, serverName)

  val serialized = objectMapper.writeValueAsBytes(testDto)
  println(String(serialized))
  // Expected output: {"id":1,"serverName":"TEST"}
  // Actual output: {"id":1,"serverName":{"value":"TEST"}}

  val deserialized = objectMapper.readValue(serialized, Any::class.java) // Because of RedisSerializer
  println(deserialized)
  // Expected output: TestDto(id=1, serverName=ServerName(value=TEST))
  // Actual output: Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: class ServerName cannot be cast to class java.lang.String (ServerName is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap') (through reference chain: TestDto["serverName"])
}

Expected behavior

No response

Additional context

No response

[cowtowncoder]

Kotlin issues belong under jackson-module-kotlin in general, will transfer.

[k163377]

Created a PR because I found a problem with databind.
FasterXML/jackson-databind#4749

Will check again after this is merged.

[k163377]

Checked.

This is a new feature addition and an implementation policy should be discussed.
I am not familiar with this feature and would like to hear any opinions on the implementation policy.

---

@effx13 has submitted “serverName”: “TEST” as an expectation, but I disagree with this for now.

kotlin-module treats properties defined in value class as if they were typed.
If so, shouldn't “serverName”:[“${type name}”, “TEST”] be the expected value?

As for the implementation, the base class of ValueClassUnboxSerializer will be changed to StdScalarSerializer.
The following is a tentative test for the prototype.

import com.fasterxml.jackson.annotation.JsonCreator
import com.fasterxml.jackson.annotation.JsonTypeInfo
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.databind.jsontype.BasicPolymorphicTypeValidator
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
import com.fasterxml.jackson.module.kotlin.registerKotlinModule
import kotlin.test.Test

class GitHub819 {
    @JvmInline
    value class ServerName(val value: String) {
        companion object {
            @JsonCreator
            @JvmStatic
            fun fromValue(value: String): ServerName {
                return ServerName(value)
            }
        }
    }

    data class TestDto(
        val serverName: ServerName
    )

    // on EVERYTHING
    @Test
    fun everything() {
        val objectMapper = ObjectMapper()
            .registerKotlinModule()
            .registerModule(JavaTimeModule())
            .activateDefaultTyping(
                BasicPolymorphicTypeValidator.builder().allowIfBaseType(Any::class.java).build(),
                ObjectMapper.DefaultTyping.EVERYTHING,
                JsonTypeInfo.As.PROPERTY,
            )

        val serverName = ServerName("TEST")
        val testDto = TestDto(serverName)

        val serialized = objectMapper.writeValueAsString(testDto)
        // -> {"@class":"com.fasterxml.jackson.module.kotlin.test.github.GitHub819$TestDto","serverName":["com.fasterxml.jackson.module.kotlin.test.github.GitHub819$ServerName","TEST"]}
        println(serialized)

        val deserialized = objectMapper.readValue(serialized, Any::class.java) // Because of RedisSerializer
        // -> TestDto(serverName=ServerName(value=TEST))
        println(deserialized)
    }
}

As a side note, as far as the prototype is concerned, I feel that it would be difficult to implement in any other way.

[effx13]

@k163377
Thank you for check my issue.

I agree, as you said, in BasicPolymorphicTypeValidator it should come out as “serverName”:[“${type name}”, “TEST”].
so is it correct that this feature is not implemented yet? I tried various methods, but I was unable to serialization and deserialization on BasicPolymorphicTypeValidator.

[k163377]

I agree, as you said, in BasicPolymorphicTypeValidator it should come out as “serverName”:[“${type name}”, “TEST”].

👍

so is it correct that this feature is not implemented yet?

First, a version that incorporates the fix for the bug is required(2.18.1 or later).

After that, you may be able to solve your use case by setting up a custom serializer based on StdScalarSerializer.

As for the kotlin-module, the changes could be small, but require a lot of testing.

[cowtowncoder]

Quick note: 2.18.1 not yet released; will be released in near future (2-3 weeks), but need to combine with other fixes.