Coercion shouldn't be necessary for Enums specifying an empty string #4896
Description
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- I searched in the issues and found nothing similar.
Describe the bug
Trying to deserialise:
{ "example": "" }Results in:
Cannot coerce empty String ("") to `YesOrNoOrEmpty` value (but could if coercion was enabled using `CoercionConfig`)
Despite an empty string ("") being listed as a value in the enum.
enum class YesOrNoOrEmpty(val value: kotlin.String) {
@JsonProperty(value = "")
EMPTY(""),
@JsonProperty(value = "yes")
YES("yes"),
@JsonProperty(value = "no")
NO("no");
}I'm trying to deserialise historical values, so this is a value I have to support. Ideally I'd still like to deserialise to an enum rather than just into a string, and would like to avoid coercion if possible.
Given that I'm specifying the empty string explicitly with @JsonProperty(value = ""), I'm assuming encountering this exception is a bug rather than intended behaviour?
Version Information
2.18.2
Reproduction
Read:
{ "example": "" }into an Example object like:
data class Example(
val example: YesOrNo
)
enum class YesOrNo(val value: kotlin.String) {
@JsonProperty(value = "")
EMPTY(""),
@JsonProperty(value = "yes")
YES("yes"),
@JsonProperty(value = "no")
NO("no");
}
Expected behavior
Deserialisation works.
Additional context
A workaround does exist (as the exception message suggests):
import com.fasterxml.jackson.databind.cfg.CoercionAction
import com.fasterxml.jackson.databind.cfg.CoercionInputShape
import com.fasterxml.jackson.databind.type.LogicalType
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder
@Configuration
class JacksonConfig {
@Bean
fun jsonCustomizer(): Jackson2ObjectMapperBuilderCustomizer {
return Jackson2ObjectMapperBuilderCustomizer { builder: Jackson2ObjectMapperBuilder ->
builder.postConfigurer { objectMapper ->
objectMapper.coercionConfigFor(LogicalType.Enum)
.setCoercion(CoercionInputShape.EmptyString, CoercionAction.TryConvert)
}
}
}
}