Le 2012-09-06 00:38, Gilles Sadowski a écrit :
On Wed, Sep 05, 2012 at 08:16:34PM +0200, Luc Maisonobe wrote:
Le 05/09/2012 19:09, Ole Ersoy a écrit :
> Hi Gilles,
>
> On 09/04/2012 06:48 PM, Gilles Sadowski wrote:
>> Hello.
>>
>> There are ideas that sound good we experiment with them within a
limited
>> framework (like a course on programming, for example); and then
become a
>> nightmare when you find yourself constantly trying to get around
them.
>> I mean that a design idea might look nice, and only when you are
long way
>> into implementing the consequences of that idea, you discover
that it was
>> not such a good one after all.
>
> Been there :)
>
>>> As a user of commons math I think it would be great if a each
exception
>>> mapped to a "One of a kind problem". So instead of having a
>>> NegativeIntegerException, which is generic and could be used in
a lot
>>> of places, have SuperDuperOptimizerNegativeIntegerException,
which is
>>> only thrown in one place.
>>>
>>> Is this possible?
>>
>> Possible, it is. But have you imagined how many different
exceptions that
>> would entail?
>
> I really did and thought maybe this is just crazy.
>
>> Currently, there are more than 1000 "throw" statements in CM.
>>
>> My position is to have a mapping between "exception type" and
"problem
>> kind"; your suggestion looks like a mapping between "exception
type" and
>> "problem location".
>
> I would rephrase my suggestion as a mapping between "exception
type" and
> "solution". So if you know the exception type, you immediately
know how
> to provide options to the person responsible for the operation.
>
>> Besides the drawback of an enormous increase of the number of
classes,
>> tying
>> the exception to its place of use is redundant with the
information
>> already
>> provided in the stack trace.
>
> I agree. I really meant "Solution". It seems that we are already
at
> the point where exceptions should provide parameters from the
instance
> that threw the exception for the purpose of UI display, logging,
etc.,
> so if it's going to be that specific, then why not make it so
specific
> that it can only have one possible message and one set of
solutions
> specific to the context.
>
>>
>> [One of the most useful rules in programming is code reuse; it
would be a
>> waste of a programmer's time to create a new exception class just
because
>> it is intended to be thrown from a different place.]
>
> I agree.
>
> The main reason I threw my 2 cents in is because it seem like the
design
> of the exceptions was getting very complicated with the inclusion
of
> localization, unrolling of diagnostic contexts (Not sure if I said
that
> right...), etc. and there has to be a simpler way.
>
> For example it seems like localization should be worried about
after you
> catch the exception and you know what to do with it. I like that
> localization is part of commons math, but to me it seems that it
should
> be a utility that can be used for message display once an action
has
> been decided upon post catching the exception. Right now it seems
that
> localization has become a constraint on exception design.
Looking at localization after the exception has been caught is
possible
only once you are sure all exceptions are unique (which is the core
of
your proposal). As our use and reuse exceptions everywhere, this is
simply not possible.
I'm not so sure that every exception must have a single use. In fact,
it
may be a quite appropriate usage of your request: Assuming that the
"getPatterns" and "getArguments" methods are available, what we do
now
(formatting of the exception message) inside the "getMessage" of
"ExceptionContext" can be done after catching the exception:
try {
// Computations that can throw CM exceptions.
} catch (MathRuntimeException e) {
if (allIsLost) {
// Build a localized message.
final List<LocalizedFormats> patterns =
e.getContext().getPatterns();
final List<Object[]> args = e.getContext().getArguments;
final String msg = TranslatorService.buildMessage(patterns,
args);
// Rethrow.
throw new UserException(msg);
}
// Handle the exception at this level.
}
[The "TranslatorService" would not be part of CM, but a side project
only depending on a "MessagePattern" enum provided by CM.]
This would be fine to me as long as without the service we could still
have humanly readable
messages in (Apache) English.
We could even revive an old Commons project for that (i18n in the
sandbox, and it could even
depend on cal10n you proposed years ago).
Did I overlook something obvious (e.g. a "nice idea that is not
so"...)?
getLocalizedMessage is not a [math] specific thing, it belongs to the
regular Java API. It
is used by debuggers in integrated development environments.
So your exemple above should probably be rewritten to provide both the
raw and the localized
message. Simply building UserException with a translated fixed String
is not enough. But moving
all the framework we have set up (and which does support this feature)
in a side project so
users can build their exceptions from that would be fine.
What I find nice (caveat notwithstanding) is that it would take the
load of
localization off CM. ["LocalizedFormats" just needs to be a
"MessagePattern"
without being "Localizable"]. We'd just keep the formatting of the
default
(English) message.
Yes.
best regards,
Luc
Regards,
Gilles
P.S. This is _not_ a proposal. ;-)
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