MismatchedInputException: Cannot construct instance when deserialising class with inline field

[markth0mas]

I've been playing around with Kotlin 1.3 features, and decided to give inline classes a try. With Kotlin 1.3M2 it was possible to serialise and deserialise classes with fields that are inline classes. I just tried them again with Kotlin 1.3 final (1.3.0), and noticed that deserialisation no longer works (serialisation is okay). The Kotlin 1.3 RC release notes mention a change in the binary representation of inline classes, so I guess that could be the root cause.

I've put together a minimal test class to illustrate:

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.readValue
import com.fasterxml.jackson.module.kotlin.registerKotlinModule
import org.junit.Assert.assertEquals
import org.junit.jupiter.api.Test

class InlineClassJsonSerialisation {
    @Test
    fun roundTripJson() {
        val objectMapper = ObjectMapper().registerKotlinModule()

        val person = Person(Name("Mark"))
        val json = objectMapper.writeValueAsString(person)

        println("json = $json")

        val parsedPerson = objectMapper.readValue<Person>(json)
        assertEquals(person, parsedPerson)
    }
}

inline class Name(val value: String)

data class Person(val name: Name)

--
If you run this, the test will fail on when calling 'objectMapper.readValue':

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of 'Person' (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (String)"{"name":"Mark"}"; line: 1, column: 2]

[Leopard2A5]

I have the same issue.

[Blackdread]

any news on this issue?

org.springframework.core.codec.CodecException: 
Type definition error: [simple type, class org.xxxx.api.xxxx.Name]; 
nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
Cannot construct instance of `org.xxxx.api.xxxx.Name` 
(no Creators, like default construct, exist): 
cannot deserialize from Object value (no delegate- or property-based Creator)

Inline classes are still not "released" but why is there issues to read from json?
Those fields are compiled are normal java field (inline class Name(val value: String) => String)

[StephenOTT]

has anyone found a workaround to this?

[junkdog]

has anyone found a workaround to this?

a no-arg constructor seems to do the trick, but it's not really a satisfactory workaround in our case

[cami-la]

has anyone found a workaround to this?

a no-arg constructor seems to do the trick, but it's not really a satisfactory workaround in our case

Thank you! It's worked.

[doriancodes]

I found this (although might not work in Kotlin) https://stackoverflow.com/questions/55529028/jackson-deserialization-error-mismatchedinputexception . Basically adding the annotation @JsonCreator to the inline class Name might work

[dinomite]

Interesting, I wonder if that annotation causes the Kotlin compiler to generate different bytecode such that the constructor is available for introspection at runtime. I think looking into that would be a good step towards finding a solution for supporting inline classes.

[k163377]

This issue is closed as the issue regarding deserialization support for value class related content will be summarized in #650.