Hey all,
I have a problem when using reflections to create an instance of an object and then setting it as a member also through reflections. This problem only occurs with typed arrays. Here is a minimal viable code example showing my problem:
import kotlin.reflect.KClass
import kotlin.reflect.KMutableProperty
import kotlin.reflect.full.createInstance
import kotlin.reflect.full.memberProperties
data class DataClassWithArray (var array: Array<InnerArrayType> = arrayOf())
data class DataClass (var array: ArrayList<InnerArrayType> = arrayListOf())
data class InnerArrayType(val data: Int = 0)
fun main() {
val dataClass = DataClass()
dataClass::class.memberProperties.forEach { kProperty ->
if (kProperty is KMutableProperty<*>) {
val arrayList = arrayListOf((kProperty.returnType.arguments[0].type!!.classifier as KClass<*>).createInstance())
println("Working with Kotlin class: ${arrayList::class} and java class ${arrayList::class.java.name}")
kProperty.setter.call(dataClass, arrayList)
}
}
val dataClassWithArray = DataClassWithArray()
dataClassWithArray::class.memberProperties.forEach { kProperty ->
if (kProperty is KMutableProperty<*>) {
val array = arrayOf((kProperty.returnType.arguments[0].type!!.classifier as KClass<*>).createInstance())
println("Failing with Kotlin class: ${array::class} and java class ${array::class.java.name}")
kProperty.setter.call(dataClassWithArray, array)
}
}
}
The code results in the following output:
Working with Kotlin class: class java.util.ArrayList and java class java.util.ArrayList
Failing with Kotlin class: class kotlin.Array and java class [Ljava.lang.Object;
Exception in thread "main" java.lang.IllegalArgumentException: argument type mismatch
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at kotlin.reflect.jvm.internal.calls.CallerImpl$Method.callMethod(CallerImpl.kt:97)
at kotlin.reflect.jvm.internal.calls.CallerImpl$Method$Instance.call(CallerImpl.kt:113)
at kotlin.reflect.jvm.internal.KCallableImpl.call(KCallableImpl.kt:106)
at TestKt.main(Test.kt:27)
at TestKt.main(Test.kt)
Somehow the java class of the array is Object-Array instead of InnerArrayType-Array. This seems to lead to an error when trying to invoke the setter of the member through reflections. This only occurs with arrays. Is this behavior intentional? I couldn’t find any documentation about it.