如何通过反射从父类调用子类方法

Question

I want to create a menu which should be populated by arbitrary methods, which are marked by an annotation. The methods should be invoked from inside the base class. Unfortunately 'java.lang.ClassCastException' is thrown since the method.invoke function expects an object which is instance of the child class. But i only get the base class.

Here is what i tried so far :

public abstract Class BaseClass{

    private void invokeSomeMethod(){
        final Method[] methods= getClass().getDeclaredMethods();

        for (Method method : methods) {
            if (method.isAnnotationPresent(MenuFunction.class)) {
                MenuFunction menuFunction = method.getAnnotation(MenuFunction.class);
                menuFunction.invoke(this); //Throws 'java.lang.ClassCastException' 
            }
        }
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ METHOD })
    public @interface MenuFunction {
        String Label();
    }

}

public Class ChildClass extends BaseClass{

     @MenuFunction(Label = "First method")
    public void setHigh(){
      //Arbitrary function 
    }

    @MenuFunction(Label = "Another method")
    public void setLow(){
      //Do something
    }

}

Answer 1

I guess what you want to do is this:

public abstract class BaseClass {

public void invokeSomeMethod() throws InvocationTargetException, IllegalAccessException {
    final Method[] methods = getClass().getDeclaredMethods();
    for (Method method : methods) {
        if (method.isAnnotationPresent(MenuFunction.class)) {
            MenuFunction menuFunction = method.getAnnotation(MenuFunction.class);
            method.invoke(this); //invoke method here'
        }
    }
}

}

public class ChildClass extends BaseClass{

    @MenuFunction(Label = "hello")
    public void hello() {
        System.out.println("hello");
    }
    public static void main(String[] args) throws InvocationTargetException, IllegalAccessException {

        new ChildClass().invokeSomeMethod();
    }
}

Result:

hello