How does one handle a java method which returns a non-public sub-type via reflection?

[Peter Levart]

On 01/15/2018 11:02 PM, David Holmes wrote:
> I recall a very similar discussion in the past. You have to start with 
> (public) statically known types, not with the dynamic type of the 
> instances involved. In essence you have to reflectively emulate the 
> method resolution process that occurs with a direct call and which 
> uses static type information.
>
> David
> ----- 

Exactly, and in the example given by Jeffrey:


javafx.scene.control.Button button1 = ...;
javafx.scene.layout.VBox vbox = ...;

vbox.getChildren().add(button1);


The right translation of the last line to reflective invocations would 
be this (skipping exception handling):


Method getChildrenMethod = 
javafx.scene.layout.VBox.class.getMethod("getChildren");
Object children = getChildrenMethod.invoke(vbox);

Method addMethod = getChildrenMethod.getReturnType().getMethod("add", 
javafx.scene.control.Button.class);
addMethod.invoke(children, button1);


You see, the compiler (javac) uses static type information (of the 
locals for example) to locate the correct method. In case of method 
chaining, it uses the declared return type of the previous method, etc...

Regards, Peter