RE: Exceptions (was: RE: [Avalon4:PROPOSAL] Context Consensus)

> From: Noel J. Bergman [mailto:[email protected]]
> 
> Leo wrote:
> > True, but here we're really going into whether RuntimeExceptions
> > should be tested for and caught.
> 
> Personally, I have an extremely dim view of the lazy use of 
> RuntimeException
> instead of properly declaring exceptions in the interface.  
> Debugging them
> in client code is a PITA as it is, and in this case because 
> we are dealing
> with a dynamic assembly model, the an end user deployment may 
> be calling a
> component that the developer has never seen.


Its a PITA any way you look at it.


> In this case, the Container is passing in a narrow type with 
> the expectation
> that the class will downcast it.  Personally, I *would* recommend the
> try-catch coding pattern, and doing it immediately in contextualize.

Yep, or at the *very least* casting it immediately in contextualize so
that the container can catch that problem.

> Berin Loritsch wrote:
> > A *Container* needs to be able to recover from ALL exceptions
> > thrown by components.  This is a real practical requirement.  If
> > a poorly written optional component introduces a 
> NullPointerException
> > or a ClassCastException, and the container does not catch it and
> > recover from it then the whole application will fail.
> 
> I agree that container (and all platform code) should be 
> robust.  But here's
> a rub.  There is no guarantee that the Component won't take 
> the Context,
> squirrel it away, and cast the thing later when it needs it.  
> And when THAT
> happens, who sees the ClastCastException?  Quite likely some other
> component, whom is not expecting those kinds of internal 
> errors to leak out.

And then the component fails regarding its contracts...  Anyway
I consider the practice a fragile contract at best.