15 Jan
2016
15 Jan
'16
12:15 p.m.
[snip]
Note that I’d like to change a bit the proposal and instead of making the exception
available from a script service, I’d prefer to make it available as a known velocity
binding such as $lastException. There’s no reason to use a script service since that would
mean it would work for all scripts and in this case we only want it to work for Velocity.
Since there’s no way to get the Velocity Context from within an uberspector, I’ll get it
by using our Component Manager and get the VelocityManager component and call
getVelocityContext()… If you know a better way, let me know.
hmm… this would mean that I’d need to put this new uberspector in xwiki-platform since
VelocityManager is in platform ATM… (@Thomas: our discussion of yesterday ;)).
There’s an alternative, which is to modify our implementation of VelocityEngine.evaluate()
and decorate the source with a #try() directive so that it’s always called (and make sure
that calling it nested won’t affect it for backward compat).
This could be simpler to implement and doesn’t force us to move some velocity code to
platform.
WDYT?
Thanks
-Vincent
[snip]
> >>
> Hi devs,
> >> >
> >> > Right now our strategy is for script services and script APIs in
general
> >> > to catch exceptions, store them and offer a getLastError() method to
get
> >> > them (see
> >> >
http://extensions.xwiki.org/xwiki/bin/view/Extension/Script+Module#HBestPra…
> >> > )
> >> >
> >> > However it would be much nicer to:
> >> > * Let our script services generate exceptions
> >> > * Offer a velocity script service to get the last exception raised by
a
> >> > java call from velocity
> >> > * Implement this uberspector to catch the exceptions and to set them
in
> >> > the execution context
> >> >
> >> > That should be quite easy to implement IMO.
> >> >
> >> > WDYT?
> >> >
> >>
> >> +1, it's a pain to call setLastError() everywhere there can be an
exception
> >> thrown, and we almost always forget to do it (for this reason).
> >>
> >> Note that we also have the #try() directive now.
> >
> > Yes, I should have mentioned that there’s indeed also this possibility:
> > * Have script API throw Exceptions
> > * Force velocity script users to wrap their code with the try directive when
they need to catch exceptions
> >
> > I still believe that the use of the Exception-catching uberspector is better.
> >
> > WDYT?
>
> Does it mean you plan to get rid of new #try directive ? Because it
> will be broken with this new uberspector.
That’s a good point, I had not thought about the implementation at this stage.
I think this could still work. When the #try directive is used I’d just have to setup
some flag somewhere in Velocity and in the uberspector I could check if this flag is set
and if so then don’t catch the exception.
Actually, thinking more, I think you’re right and that the #try directive plays exactly
the same role as an Exception-catching uberspector and I don’t see the need for the #try
directive if we provide an uberspector.
So I’m proposing to deprecate it but still keep it for backward compatibility for now
(probably a full cycle).
WDYT?