Javax Validation Custom enum constrains in Kotlin - validation

Question

I'm trying to create a custom annotation and validator to use in conjunction with the javax validation Api and I'm having trouble access the values of an enum.
The objective of the annotation and the validator is validate if an input data is present within the enum values.
This is the annotation class
import javax.validation.Constraint
import javax.validation.Payload
import kotlin.reflect.KClass
#kotlin.annotation.Target(
AnnotationTarget.FIELD,
)
#kotlin.annotation.Retention(AnnotationRetention.RUNTIME)
#MustBeDocumented
#Constraint(validatedBy = [ValueOfEnumValidator::class])
annotation class ValueOfEnum(
val enumClass: KClass<Enum<*>>,
val message: String ="",
val groups: Array<KClass<*>> = [],
val payload: Array<KClass<out Payload>> = []
)
This is the validator implementation
import javax.validation.ConstraintValidator
import javax.validation.ConstraintValidatorContext
class ValueOfEnumValidator: ConstraintValidator<ValueOfEnum, CharSequence> {
private val acceptedValues: MutableList<String> = mutableListOf()
override fun initialize(constraintAnnotation: ValueOfEnum) {
super.initialize(constraintAnnotation)
acceptedValues.addAll(constraintAnnotation.enumClass.java
.enumConstants
.map {it.name}
)
}
override fun isValid(value: CharSequence?, context: ConstraintValidatorContext): Boolean {
return if (value == null) {
true
} else acceptedValues.contains(value.toString())
}
}
I'm aiming to use annotation like this:
#field:ValueOfEnum(enumClass = SortDirectionEnum::class, message = "{variants.sorted.sort.direction.not.valid}")
var sortDirection:String?=
But my IDE is reporting me the following error in the enumClass parameter
Type mismatch.
Required:KClass<Enum<*>>
Found:KClass<SortDirectionEnum>
How can I make the annotation generic enough to support different enums, and fix this issue ?

Answer 1

You are restricting enumClass to instances of Enum<*>, allowing Enum instances (Enum is an abstract class though, so nothing can be used) with all types of data, you however want to also allow child classes of Enum, which can be achieved with the out keyword there.
val enumClass: KClass<out Enum<*>>,
https://kotlinlang.org/docs/generics.html