Jackson deserialization of missing JSON number value to 0.0 in Spring

Question

I have defined a Kotlin data class like this:

@JsonIgnoreProperties(ignoreUnknown = true)
data class MandatoryLimits(

  val upper: Double,

  val lower: Double

)

as part of a compound object that my Spring service receives as a request body in a POST request. When I send a test request with one value missing, e.g. like this:

           "specificationLimits": {
                "lower": 1.6
            }

then I receive a correctly deserialised object of Type MandatoryLimits, but the missing value is set to simply 0.0.

I would have expected to get a BAD REQUEST from the service, instead. Do I need to configure something in addition?

Thanks in advance for all your help!

Answer 1

To fail deserialization when a Kotlin primitive is null, you need to make sure the DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES Jackson configuration flag is active.

Below is an example of ObjectMapper bean configuration that will throw an error when it tries deserializing a null Kotlin primitive.

@Configuration
class JacksonConfig {
    @Bean
    fun objectMapper(): ObjectMapper {
        return jacksonObjectMapper()
            .configure(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, true)
    }
}