Non-nullable Long Kotlin data class field initialized with 0 when field is missing in payload

[erkieh]

Expected Behavior

Posting validated HTTP JSON Payloads with missing values for Non-nullable Long Kotlin data class fields should result in a 400 bad request response,

Actual Behaviour

Non-nullable Long Kotlin data class fields are initialized with 0 when the field is missing in the payload. Strings for example behave differently. They don't get defaulted. Instead the result will be an 500 Internal server error with a NullPointerException happening on the server side.

Steps To Reproduce

Run tests in sample app

Environment Information

Windows 10 Java 21

Example Application

git@github.com:erkieh/demonullhandling.git

Version

4.5.0-SNAPSHOT

[roar-skinderviken]

This issue seems to be related to this issue except for that

• missing String-value in JSON causes NPE, while missing Long-value like in this issue, gives Long default value (0)
• this behavior seems to be unchanged across MN:4.x versions

Please note that any default values in Kotlin data classes are ignored during deserialization in this issue.

A possible workaround for returning 400 bad request when Long-value is missing in JSON, may be to use @Min along with @Bindable annotations (given that only non-negative numbers are valid):

import io.micronaut.core.bind.annotation.Bindable
import io.micronaut.serde.annotation.Serdeable
import jakarta.validation.constraints.Min

@Serdeable
data class NonNullDto(
    @Min(0L)
    @Bindable(defaultValue = "-1")
    val longField: Long
)

Tests

import com.deserializenull.rest.dto.NonNullDto
import com.deserializenull.rest.dto.NullDto
import io.kotest.assertions.throwables.shouldThrow
import io.kotest.core.spec.style.StringSpec
import io.kotest.matchers.shouldBe
import io.micronaut.http.HttpRequest
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.test.extensions.kotest5.annotation.MicronautTest

@MicronautTest
class NonNullDtoControllerTest(
    @Client("/") httpClient: HttpClient
) : StringSpec({

    "test deserialization with null data, expect 400 response" {
        val exception = shouldThrow<HttpClientResponseException> {
            httpClient.toBlocking().exchange(HttpRequest.POST("/nonnulldto", NullDto()), NullDto::class.java)
        }

        exception.status.code shouldBe 400
    }

    "test deserialization with valid data, expect 200 response" {
        val response = httpClient.toBlocking().exchange(HttpRequest.POST("/nonnulldto", NonNullDto(longField = 1)), NonNullDto::class.java)
        val responseBody = response.getBody(NonNullDto::class.java).get()

        response.status.code shouldBe 200
        responseBody.longField shouldBe 1
    }
})

[dstepanov]

Please create / update the sample app with your use case

[dstepanov]

The behaviour is the same as a default in Jackson. The fix is a configuration to fail on null primitives.