Jackson , defaulting empty or null value of boolean field to false

Question

I am using Kotlin Springboot stack and in a rest controller we have a request body model with field "isAgent" which is boolean.

The ask is to fail if the request is not having this boolean field.

We checked that, if we annotate @JsonProperty(required = true) over the field. Jackson fails saying required parameter is not passed , which is inline with the ask. But when fields is passed with "" OR " " OR Null value , jackson defaults it to false , but we want to fail this.

Any Idea how to achieve this in SpringBott without implementing custom Deserializer.

Answer 1

You can define a custom ObjectMapper bean setting DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES to true

import com.fasterxml.jackson.databind.DeserializationFeature
import com.fasterxml.jackson.databind.ObjectMapper

import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.context.annotation.Primary

@Configuration
class JacksonConfig

    @Bean
    @Primary
    fun objectMapper(): ObjectMapper {
        return ObjectMapper()
            .configure(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, true)
    }
}

Then a Request class like below would fail deserialization if isUserAgent is missing or null or blank

data class Request(
    @JsonProperty(value = "isUserAgent", required = true)
    val userAgentSpecified: Boolean,
)

Tests verifying the deserialization can be found on github