CODEWITHSUNDEEP
kotlinannotation-processing
Patrick
Patrick

Reputation: 876

Is there a way to force using annotation only on a var property

I'm making an annotation processor for encrypting personal data due to law. So in order to encrypt those field it should be able to set new value so I want my annotation to force using only on a var property.

@Retention(AnnotationRetention.RUNTIME)
@Target(AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER)
annotation class PersonalData {
}

data class CreateAccountCommand(
  @PersonalData
  var fullname: String // it would throw an error if using val since it's not mutable
)

class TestAnnotation {
  @Test
  fun testFindAnnotation() {
    val message = EasyRandom().nextObject(CreateAccountCommand::class.java)
    val wrappedCommand = GenericCommandMessage.asCommandMessage<CreateAccountCommand>(message)
    if (isPersonalDataPresent(wrappedCommand.payload)) {
      encryptData(wrappedCommand.payload)
      wrappedCommand.payload.fullname shouldContain "-encrypted"
    }
  }

  private fun isPersonalDataPresent(payload: Any): Boolean {
    return payload::class.memberProperties.any {
      it.annotations.any { ann -> ann.annotationClass == PersonalData::class }
    }
  }

  private fun encryptData(payload: Any) {
    payload::class.memberProperties.map {
      if (it is KMutableProperty<*>) {
        it.setter.call(payload, "${it.getter.call(payload)}-encrypted")
      }
    }
  }
}

or any better way?

Upvotes: 0

Views: 357

Answers (1)

Sweeper
Sweeper

Reputation: 271310

If you only include PROPERTY_SETTER in the annotation targets, the annotation can only be applied to property setters, which is effectively what you want - since a property setter implies a mutable property.

@Retention(AnnotationRetention.RUNTIME)
@Target(AnnotationTarget.PROPERTY_SETTER)
annotation class PersonalData

When using this annotation, you'd usually have to specify the use site target:

data class CreateAccountCommand(
    @set:PersonalData
    var fullname: String
)

Changing it to val would give you an error, just like you expect, because a val does not have a setter.

isPersonalDataPresent also needs a little modification, to check whether the setter has the annotation:

return payload::class.memberProperties
    .filterIsInstance<KMutableProperty<*>>()
    .any {
        it.setter.annotations.any { ann ->
            ann.annotationClass == PersonalData::class
        }
    }

Upvotes: 2

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