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From Dan Creswell <dan.cresw...@gmail.com>
Subject Re: River exception usage.
Date Thu, 18 Oct 2012 18:02:02 GMT

I've been trying to put this into words for a while, Greg hit's the mark
for me where I couldn't...

On 18 October 2012 16:20, Greg Trasuk <trasukg@stratuscom.com> wrote:

> To be specific, you're talking about (for example) making
> TransactionException and LeaseException, and have them both extend
> RiverException.  I don't like this idea for a number of reasons:
> First, as an old-time Jini-er, I still cling to the idea of Jini as a
> set of standards, and River as an implementation of those standards.  We
> often talk about this division informally as "the API" or "the Specs",
> and "the implementation".  So I don't like the idea of the name 'River'
> bubbling through the API layer.
> But to be clear, I still wouldn't like it if we defined a
> "JiniException".
> I'm probably not going to express my concerns very well - it's more of a
> "code smell" sort of thing.  A better architect than me would probably
> know the exact name for the API design principle involved, but it seems
> like we're mixing the problem domain and the solution domain, where the
> exception hierarchy should mostly reflect the problem domain.
> Specifically, to use the exceptions I mentioned above:  LeaseException
> and TransactionException don't have any commonality or relationship in
> the problem domain, except that they are both exceptions.  They are
> products of two separate specifications that address different and
> orthogonal aspects of the distributed programming problem space.  To
> give them a common ancestor in RiverException would be imposing the
> solution-side concept that they happen to both be defined in the same
> Apache project.  To me, that doesn't seem like good API design.
> I'm all for reasonable exception hierarchy.  For example, LeaseException
> is the parent of LeaseDeniedException, LeaseMapException, and
> UnknownLeaseException, which makes sense, since they're all types of
> exceptions involved in leasing.  Similaryly, TransactionException is the
> superclass of CannotAbortException, CannorCommitException,
> CannotJoinException , CannotNest Exception, TimeoutExpiredException,
> etc, which also makes sense, because they are all types of exceptions
> that have to do with transactions.
> In other words, I've looked through the River codebase and from what I
> can see, the exception hierarchy already reflects a reasonable
> organization of exceptions, and to make the top-level of this hierarchy
> extend from a common exception would not make sense.  The only common
> traits of TransactionException and LeaseExceptions is that they are both
> Exceptions.  That commonality is accurately reflected by the fact they
> both subclass Exception.
> Cheers,
> Greg.
> On Thu, 2012-10-18 at 09:43, Simon IJskes - QCG wrote:
> > On 18-10-12 15:36, Gregg Wonderly wrote:
> > >> I see no problem in deriving all river exceptions that are
> > >> currently derived from Exception, now from RiverException extends
> > >> Exception. This would as far a i can see create no problems in
> > >> river as to compatibility.
> >
> > To make it more clear: To only change river exceptions that are directly
> > extending Exception.

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