Here's my take at this: I'd use exceptions as sparingly as possible and only for cases where something unexpected (an exception!) happens. That is, I wouldn't use exceptions e.g. for items not being found. This is clearly something that happens all the time and is by no means unexpected.

For the cases where exceptions are involved I would define our own very small set of exceptions and make them all *unchecked*. Checked exceptions compose very badly wrt. lazyness. For example an iterator which lazily fetches its items on next() has no clean way of handling exceptions in the next() method.

Only at the very last instance (i.e. in the jcr component) I would actually create and throw the various RepositoryExceptions.