Calling super in subclasses

Question

Is there a pattern to accomplish the following?
I have a setup() method that must be called:
class A {
  public void setup() {
    // necessary code for A
}I want to ensure its code gets executed even if a subclass overides it. The usual way is with a "hook":
class A {
  public final void setup() {
    // necessary code for A
    onSetup();
  public void onSetup() {}
}This way, a subclass can only override onSetup(), ensuring that the code in setup() gets called. However, say I want to play the same trick with subclasses of A:
class B extends A {
  public final void onSetup() {
    // necessary code for B
    onOnSetup();
  public void onOnSetup() {}
class C extends B {
  public final void onOnSetup() {
    // necessary code for C
    onOnOnSetup();
  public void onOnOnSetup() {}
}Is there a pattern I can use so that each class only has to override a method called setup(), and it is guaranteed that the code in every overidden setup() method will be called? Calling super() from within each setup() is fragile, because a subclass might forget it. Using a hook each time (as in the above example) is annoying, because each time, a different name must be assigned to the non-final method at every level in the hierarchy.

Answer 1

I have dealt with this. In keeping with the principle of not calling overridable methods in constructors, one may require such a method. For instance, I have objects that are ultimately part of a database, but when created they do not have the db object yet. So later they must be setup with the appropriate db object.
I think it is understood that overriding a method involves respecting the class you are altering. You should not override a method if you do not understand what it does. That being said, the solution here is to simply put in the comment of the method that it must always be called by any subclasses. There are lots of things which can not be forced. If one overrides this method but does not call super, they are violating the contract of the class.
You can add a private boolean isSetup, and assert if any methods are called before isSetup is true, if you wish. Personally I would throw an IdiotException :-)
If you have time to burn and want to get buck wild, you can also use the strategy pattern.
class AClass {
  private List setupers = new ArrayList();
  AClass(){
     Setuper su = new Setuper() {
          public void setup() {
               //do setup for AClass
      setupers.add(su);
  public final void setup(){
      for(Iterator it = setupers.iterator();it.hasNext();){
         ((Setuper)it.next()).setup();
       setupers = null;
class BClass extends AClass {
  BClass(){
     Setuper su = new Setuper() {
          public void setup() {
               //do setup for BClass
      setupers.add(su);
interface Setuper {
    public void setup();
}But once you start down this road, you will eventually come face to face with the fact that some things are understood and a certain amount of intelligence, no, respect is required to extend a class properly. There will always be a way to force the issue, but it will involve increasing amonts of work with little pay off. You cant save people from themselves.