Converting Kotlin's KClass to regular Class in Java

Question

I am trying call a regular Java method in a Java code as follows:

public <T> T proxy(KClass<T> kClass) { 
    // unfortunately nothing like getJavaClass() exists
    return (T) proxy(kClass.getJavaClass()); 
}

public <T> T proxy(Class<T> jClass) {
    return (T) context.getBean(jClass);
}

In Kotlin, you can call .java on each KClass. This is not the case here and I am unable to extract the Java Class object from KClass. Is there a way to do it?

EDIT: This is trivial in Kotlin, but I am looking for solution in Java code.

Answer 1

The functionality does exist, just not where it seems to, as java is an extension property.

Use the method JvmClassMappingKt.getJavaClass.

In Kotlin, extension methods (and property getters/setters) are implemented as static methods of their containing class. If you look at the source for .java (Ctrl+Q), you can see that it is implemented in JvmClassMapping.kt.

As the function is package-level and does not have a containing object, it is simply placed into the file [Filename]Kt which in this case is JvmClassMappingKt.

Here is the source of this extension property:

@Suppress("UPPER_BOUND_VIOLATED")
public val <T> KClass<T>.java: Class<T>
    @JvmName("getJavaClass")
    get() = (this as ClassBasedDeclarationContainer).jClass as Class<T>

As you can see, the method's name is renamed on the JVM to getJavaClass.

In your case, you can try:

public <T> T proxy(KClass<T> kClass) { 
    return (T) proxy(JvmClassMappingKt.getJavaClass(kClass)); 
}

Answer 2

You can try to use javaObjectType on your KClass

The explanation:

Returns a Java [Class] instance corresponding to the given [KClass] instance. In case of primitive types it returns corresponding wrapper classes.

E.g.

Boolean::class.javaObjectType