Greg, I had mentioned Spring in the original issue, as I was passingly familiar that it had switched to using RuntimeExceptions almost exclusively. It is a potential solution.
Yet because networking is one of the more failure-prone areas of the stack, Jini is more likely to be producing exceptions even in well-tested code. Moreover, also owing to the vagaries of networking, Jini is also more likely than other code to be producing _recoverable_ exceptions. This does not seem the ideal usage case for RuntimeExceptions, if you think there's a place for checked exceptions at all. I recommended a Jini or RiverException from my experience with other libraries that had similar models. Library-wide exceptions account for my best experiences with checked exceptions from libraries. Not only does the practice reduce the number of potential catch/throws statements one must write (both inside the project and in usage), but it also serve to quickly pinpoint the problem region in the code: as a developer, you're likely to have an awareness of just where Jini is being used in your code, whereas an IOException might crawl out from a greater number of call-sites. The practice is something like a "marker interface", unfortunately shoved into the proper hierarchy because Java constricts catch and throw statements in that way. James On Fri, Oct 19, 2012 at 8:11 AM, Greg Trasuk <[email protected]> wrote: > > Hi James: > > Is it possible that what you're really looking for is unchecked > exceptions, a-la Spring's "unified exception hierarchy" for data access > objects? > > Because what I hear you saying is "handling exceptions is a nuisance". > And you're right, especially when, at the user-interface level, there's > typically not much you can do about an exception except tell the user to > try again later. > > I have to confess that my personal thinking on checked vs unchecked > seems to vary over time. Generally I find I'm tending towards unchecked > exceptions except in cases where I don't feel that I can adequately > unit-test. Unfortunately that covers most of the network situations > that Jini/River is good for, so I guess that the exception handling is a > "cost of doing business". > > I've come across some good discussions on the issue at > http://www.artima.com/intv/handcuffsP.html and > http://www.mindview.net/Etc/Discussions/CheckedExceptions. > > Your concern is valid. I don't know what the best solution is. I'm > pretty sure that it isn't a single unifying exception based on the fact > that it's from the same jar file. > > Suggestions, anyone? > > Cheers, > > Greg. > > On Thu, 2012-10-18 at 16:28, James Grahn wrote: >> My concern - the reason for which I raised the issue in the first >> place - was similarly a "code smell". Individually considered, I >> agree that the current exception hierarchy is acceptable. There's a >> sound reasoning behind each part of the hierarchy. Yet my objection >> is not to the pieces, but the gestalt. >> >> Obtain a Javaspace, obtain a transaction manager, get a transaction, >> read from that space under transaction, write to that space under >> transaction, commit. How many exceptions must be dealt with for this >> minimal workflow? Multiply this by the number of times you use >> Javaspace, and you're either writing a hygiene layer to bring it under >> control or you're left with verbose, less readable code everywhere >> River touches. That, too, is a code smell. >> >> I suspect that there may be an experiential difference between those >> building their own services on top of Jini/River, and those using >> what's already there. Those who wish to add a layer on top of >> Jini/River very likely must care about every possible exception and >> handle them all individually. A unified exception hierarchy would >> not exclude those building services, but would - in my opinion - ease >> the way for raw usage in applications. >> >> An "improved new user experience" is a topic that occasionally >> surfaces on this list and I believe removing hurdles to raw usage >> would qualify under that category as well. >> >> As for the other major concern: as mentioned before, yes, this is a >> change that breaks compatibility. It would need to be reserved for a >> major version change or delayed until something else is going to break >> backwards compatibility anyway. It would also require a broad >> consensus for the change (which does not appear to be emerging). >> >> I speak only from my own experience, but this change would have been >> welcomed at the company where I worked. >> >> james >> >> On Thu, Oct 18, 2012 at 11:20 AM, Greg Trasuk <[email protected]> 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. >> > >
