Jackson Validation

build.gradle.kts

dependencies {
  implementation("org.hibernate.validator:hibernate-validator:6.1.5.Final")
  implementation("javax.el:javax.el-api:3.0.0")
  implementation("org.glassfish:javax.el:3.0.0")
}

JsonValidated.kt

import kotlin.annotation.AnnotationTarget.CLASS

@Target(CLASS)
annotation class JsonValidated

ValidatingBeanDeserializerModifier.kt

import com.fasterxml.jackson.databind.BeanDescription
import com.fasterxml.jackson.databind.DeserializationConfig
import com.fasterxml.jackson.databind.JsonDeserializer
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier
import javax.validation.Validation

object ValidatingBeanDeserializerModifier : BeanDeserializerModifier() {

    private val validator = Validation.byDefaultProvider()
        .configure()
        .buildValidatorFactory()
        .validator

    override fun modifyDeserializer(
        config: DeserializationConfig,
        beanDesc: BeanDescription,
        deserializer: JsonDeserializer<*>
    ) = if (beanDesc.classAnnotations.has(JsonValidated::class.java)) {
        ValidatingDeserializer(deserializer, validator)
    } else {
        deserializer
    }
}

ValidatingDeserializer.kt

import com.fasterxml.jackson.core.JsonParser
import com.fasterxml.jackson.databind.DeserializationContext
import com.fasterxml.jackson.databind.JsonDeserializer
import com.fasterxml.jackson.databind.JsonMappingException
import com.fasterxml.jackson.databind.deser.std.DelegatingDeserializer
import javax.validation.Validator

class ValidatingDeserializer(
    delegate: JsonDeserializer<*>,
    private val validator: Validator
) : DelegatingDeserializer(delegate) {

    override fun newDelegatingInstance(newDelegatee: JsonDeserializer<*>): JsonDeserializer<*> {
        return ValidatingDeserializer(newDelegatee, validator)
    }

    override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Any? {
        return super.deserialize(p, ctxt)?.let { validate(it) }
    }

    private fun validate(deserialized: Any): Any {
        val constraintViolations = validator.validate(deserialized)
        when {
            constraintViolations.isEmpty() -> return deserialized
            else -> {
                val message = constraintViolations.joinToString { it.message.format(it.invalidValue) }
                throw JsonMappingException(null, message)
            }
        }
    }
}

ValidatingModule.kt

import com.fasterxml.jackson.databind.module.SimpleModule
import javax.validation.Validation

class ValidatingModule : SimpleModule() {

    init {
        setDeserializerModifier(ValidatingBeanDeserializerModifier)
    }
}