CDI - Event Observers

Question

Hi all,

I have event observers which all observe the same event, so I have an abstract superclass which observes that event and then the subclass overrides / implements the specific functionality.

The problem with this is that it doesn't observe the event unless I put the event observer method in the subclass (which defeats the purpose of my design).

I can most certainly do it this way, but I want to write as little code as possible.

Should it work this way (am I doing something else wrong)?

If it isn't supposed to work this way, then I can write a producer for one thing and then an interceptor. I thought that my first approach was simpler and more likely to be used properly by other developers.

example code:

SuperClass:

public abstract class AbstractFileWriter
{
  public void onReady(@Observes ReadyEvent readyEvent)
  {
    try
    {
      handleReady(readyEvent, ...);
    }
  }

  protected abstract handleReady(ReadyEvent readyEvent, otherParameters go here);
}

SubClass

public class XmlWriter extends AbstractFileWriter
{
   protected handleReady( ... )
   { ... }
}

If I write it this way, handleReady is never invoked (and neither is onReady for that matter); however, if I write it with the observer method within the subclass, it works as expected. I want to write it this way as there is much less code I'd have to write and a little bit less abstraction which should make it easier to understand.

Walter

Answer 1

Either declare the relevant method in the superclass to be abstract or have it call an abstract "detail" method that each subclass implements.

Answer 2

I wrote a decorator as I mentioned above. This essentially does the same thing, just written slightly differently.

Walter