JSON-schema.kt

private class KotlinValidationConstraintResolver : AnnotationConstraintResolver() {
    override fun getRequired(prop: BeanProperty): Boolean? = super.getRequired(prop) ?: isNullable(prop) == false
}

private fun isNullable(prop: BeanProperty): Boolean? = when (prop) {
    is BeanPropertyWriter -> prop.isNullable()
    else -> null
}

private fun BeanPropertyWriter.isNullable(): Boolean? {
    val member: Member = member.member
    return when (member) {
        is Method -> {
            member.declaringClass.findPropertyWithName(this.name)?.returnType?.isMarkedNullable
        }
        else -> null
    }
}

private fun Class<*>.findPropertyWithName(name: String): KProperty<*>? = this.kotlin.memberProperties.find { it.name == name }

val generator = JsonSchemaGenerator(objectMapper, ValidationSchemaFactoryWrapper(KotlinValidationConstraintResolver())