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Using java.lang.Integer as Field Type

See original GitHub issue


Once I convert this

case class SomeClass (
 someField: Int


case class SomeClass (
 someField: java.lang.Integer

I start getting an error on

    for {
      ad <- Gen.oneOf(random[SomeClass](testsNum))
    } yield {

which is below.

Error:(17, 49) not enough arguments for method random: (implicit evidence$3: reflect.runtime.universe.WeakTypeTag[SomeClass], implicit evidence$4: org.scalacheck.Arbitrary[SomeClass])Seq[SomeClass].
Unspecified value parameter evidence$4.
      ad <- Gen.oneOf(random[SomeClass](testsNum))
Error:(17, 49) could not find implicit value for evidence parameter of type org.scalacheck.Arbitrary[SomeClass]
      ad <- Gen.oneOf(random[SomeClass](testsNum))

Could you help understanding how to tackle that? Sorry for the noise.

Issue Analytics

  • State:closed
  • Created 4 years ago
  • Comments:10 (3 by maintainers)

github_iconTop GitHub Comments

pete-protoncommented, Feb 6, 2020

I found a way to stick with Ints and it made the life way easier. The workaround is below

import com.fasterxml.jackson.databind.{ BeanProperty, DeserializationContext, JsonDeserializer }
import com.fasterxml.jackson.databind.deser.ContextualDeserializer
import com.fasterxml.jackson.databind.deser.std.StdDeserializer
import javax.annotation.Nonnull
import scala.reflect.ClassTag

abstract class NonNullDeserializer[T](
  nullable: Boolean = true,
  fieldName: String = null)(implicit classTag: ClassTag[T])
  extends StdDeserializer[T](classTag.runtimeClass)
  with ContextualDeserializer {

  def createContextual(
    ctxt: DeserializationContext,
    property: BeanProperty): JsonDeserializer[_] = {
    val isNullable = property.getAnnotation(classOf[Nonnull]) == null
    val fieldName = property.getName

    createContextual(isNullable, fieldName)

  protected def createContextual(
    isNullable: Boolean,
    fieldName: String): JsonDeserializer[T] = {
    val constructor = getClass.getConstructor(classOf[Boolean], classOf[String])

      .newInstance(java.lang.Boolean.valueOf(isNullable), fieldName)

  override def getNullValue(ctxt: DeserializationContext): T = {
    if (!nullable) {
      ExceptionHandler.nullFieldValueFieldErr(fieldName) // handling nullability here
import com.fasterxml.jackson.core.JsonParser
import com.fasterxml.jackson.databind.DeserializationContext

class NonnullIntDeserializer(
  nullable: Boolean = true,
  fieldName: String = null)
  extends NonNullDeserializer[Int](nullable, fieldName) {

  override def deserialize(
    p: JsonParser,
    ctxt: DeserializationContext): Int = {
    super._parseIntPrimitive(p, ctxt)

  override def getNullValue(ctxt: DeserializationContext): Int = {


then install it

import akka.http.scaladsl.model.DateTime
import com.fasterxml.jackson.databind.{ BeanDescription, DeserializationFeature, JsonMappingException, ObjectMapper }
import com.fasterxml.jackson.databind.module.SimpleModule
import com.fasterxml.jackson.module.scala.DefaultScalaModule
import com.fasterxml.jackson.module.scala.experimental.ScalaObjectMapper
import javax.annotation.Nonnull
import scala.collection.JavaConversions._
import scala.reflect.ClassTag
import scala.util.Try

    val mapper = (new ObjectMapper() with ScalaObjectMapper)
      .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)

    val simpleModule = new SimpleModule()
        new NonnullIntDeserializer())

so, I guess, we can resolve the ticket, which I will do with your permission, @DanielaSfregola

DanielaSfregolacommented, Jan 30, 2020

Weird, if you are using case classes the type class derivation should have no problem in automatically generating an Arbitrary for each case class, even if nested.

I’d do some investigation and try to replicate the issue! 😃

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