[JAVA] [Kotlin] Get the argument name of the constructor by reflection

TL;DR --From KClass which can be taken by reflection of Kotlin, the argument name of the constructor can be taken with the original name. --From the Class that can be taken by the reflection of Java, the argument name of the constructor can only be taken as "ʻarg0, ʻarg1, ʻarg2... " --Even if you get theKClass from the code whose original is Java, the argument name of the constructor will be "ʻarg0, ʻarg1, ʻarg2 ..." and the original argument name cannot be taken.

things to do

Extract the argument name of the constructor from the following class.

data class Data(val sampleInt: Int, val sampleString: String)

manner

You can do it in the following two lines.

val clazz: KClass<Data> = Data::class
val parameterNames: List<String> = clazz.constructors.first().parameters.map { it.name }

println(parameterNames) // -> [sampleInt, sampleString]

Supplement

I will supplement it with the reflection of Java (I am doing it with Java8, it seems that there are changes around the reflection in later versions, but I can not follow it).

What happens if you do it with Java reflection

It will be as follows.

val clazz: Class<Data> = Data::class.java
val parameterNames: List<String> = clazz.constructors.first().parameters.map { it.name }

println(parameterNames) // -> [arg0, arg1]

What happens if you do it for a Java class

Do it for the following Java class.

@Getter //Assumption generated by lombok
public class JavaData {
    private final Integer sampleInt;
    private final String sampleStr;

    public JavaData(Integer sampleInt, String sampleStr) {
        this.sampleInt = sampleInt;
        this.sampleStr = sampleStr;
    }
}

As shown below, the argument name cannot be taken.

val clazz: KClass<JavaData> = JavaData::class
val parameterNames: List<String> = clazz.constructors.first().parameters.map { it.name }

println(parameterNames) // -> [arg0, arg1]

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