[Engine-devel] Dynamic resource loading in GWT

Wed Aug 7 13:50:02 UTC 2013

[top posting]

in general, gwt applications are not "built" for loading things at run-time. 
for the branding feature, we had to change some of that due to the feature 
requirements.

question is what will we gain from loading dynamically the values that are 
currently being loaded statically. 
for features such as dynamic/user-defined OSs [1] - it makes sense and probably 
even required, however, for error messages, which are not dynamic/user-defined, 
I think that it doesn't.
there are other ways to ease maintenance of error-messages (e.g. maintain only 
one copy of each file, and copy it during compilation time to the relevant 
locations, instead of maintaining several identical files), without introducing 
the disadvantages of dynamic loading.

----
Thanks,
Einav

[1] http://www.ovirt.org/OS_info

----- Original Message -----
> From: "Roy Golan" <rgolan at redhat.com>
> To: awels at redhat.com
> Cc: engine-devel at ovirt.org
> Sent: Wednesday, August 7, 2013 9:35:30 AM
> Subject: Re: [Engine-devel] Dynamic resource loading in GWT
> 
> On Wed 07 Aug 2013 03:23:36 PM IDT, Alexander Wels wrote:
> > On Wednesday, August 07, 2013 02:48:45 PM Roy Golan wrote:
> >> On 08/07/2013 02:08 PM, Einav Cohen wrote:
> >>> Hi Roy,
> >>>
> >>> a couple of notes (I could be totally wrong here, GWT experts - please
> >>> review/comment):
> >>>
> >>> - from [1]:
> >>> "Provides dynamic string lookup of key/value string pairs defined in a
> >>> module's host HTML page" - there is a chance that a gwt dictionary is
> >>> limited to reading key/value string pairs that reside within the *gwt
> >>> module host HTML page* (i.e., within the context of the GWT application -
> >>> "http://[server]/webadmin/webadmin/...") and not outside - need to find
> >>> that out.
> >> well the file servlet resides on [server] so I don't think there a "same
> >> origin policy" problem here - correct me if I'm wrong (isn't branding
> >> doing something similar?)
> >>
> >
> > Branding is doing exactly what you are suggesting, generating a dictionary
> > in
> > the host page, and having the GWT application read it at runtime. The only
> > reason we did it like that, is that there is no other way of changing some
> > of
> > the messages at runtime. If there was some way of doing it at compile time
> > I
> > would have done that. Also the number of resources changed by branding is
> > very
> > limited and therefore won't impact the performance as much as doing every
> > single resource.
> >
> > There are advantages and disadvantages of both methods that need to be
> > carefully weighed, and the GWT developers themselves did that and came to
> > the
> > conclusion that compile time inclusion is the best method for most
> > resources.
> > They did however anticipate the need for some runtime resources so they
> > included Dictionary etc.
> >
> >>> - again, from [1]:
> >>> "a variety of error conditions (particularly those involving key
> >>> mismatches) cannot be caught until runtime. Similarly, the GWT compiler
> >>> is unable discard unused dictionary values since the structure cannot be
> >>> statically analyzed".
> >>> (this is expected, as the suggested loading here is dynamic, rather than
> >>> static)
> >>>
> >>> - not sure exactly how this would work with localization; there is "A
> >>> Caveat Regarding Locale" mentioned in [1] - IIUC, we will lose the
> >>> automatic locale-mapping that we have today, and we would need to do it
> >>> ourselves somehow (not a big deal, I suppose, just some extra work that
> >>> needs to be done here).
> >>
> >
> > The branding allows one to define java property bundles for all the
> > supported
> > languages, and will load them at runtime and put the translated strings in
> > the
> > Dictionary in the host page. Again I wouldn't recommend doing it for a
> > large
> > number of resources.
> why?
> and what number is large?
> >
> >> indeed but it will pay off. a change off resources means ctrl+F5 and not
> >> GWT compilation :P
> >>
> >
> > Sure for the developer it would be great, less compiling. However for the
> > user
> > not so much,
> 
> isn't admin is gaining from it? and development time and bugs around
> messages?
> 
>  and in the end we are creating the software for the user and the
> > needs of the developer are secondary to that. When I say it is not so great
> > for the user, I mean the fact that it becomes a lot harder to cache the
> > host
> > page (as the contents can change), vs caching the compiled resources is
> > really
> > easy as the contents won't chance.
> 
> in the end both are cached so there is no memory overhead.
> >
> >
> >>> ----
> >>> Thanks,
> >>> Einav
> >>>
> >>> [1]
> >>> http://www.gwtproject.org/javadoc/latest/com/google/gwt/i18n/client/Dicti
> >>> onary.html
> >>>
> >>> ----- Original Message -----
> >>>
> >>>> From: "Roy Golan" <rgolan at redhat.com>
> >>>> To: "engine-devel" <engine-devel at ovirt.org>
> >>>> Sent: Wednesday, August 7, 2013 2:59:07 AM
> >>>> Subject: [Engine-devel] Dynamic resource loading in GWT
> >>>>
> >>>> Painful issue here - we all know the regular drill of maintaining
> >>>> messages in many places, I18N files and so on.
> >>>> Also there's a patch to make all available timezone an java enum and by
> >>>> that share it for free with the UI. its a way better than a backend
> >>>> Query.
> >>>>
> >>>> But this is all hard-coded, not flexible, hard to maintain, we all know.
> >>>>
> >>>> Why won't we make GWT load a javascript dictionary/dictionaries from a
> >>>> servlet or our host page html[1] using GWT Dictionary[3]?
> >>>>
> >>>> that way the configuration is shared with the engine, it relies on the
> >>>> disk, customers and GSS can change it on-site and so on.
> >>>>
> >>>> | index.html | -> | file servlet | -> |read /etc/ovirt-engine/conf/...|
> >>>> |
> >>>>        ^
> >>>> |
> >>>> | GWT loads Dictionary |
> >>>>
> >>>> candidates for dynamic resources
> >>>> * I18N resources AppErrors...
> >>>> * config ( just the UI subset )
> >>>> * osinfo ?
> >>>>
> >>>>
> >>>>
> >>>> [1] host page html -
> >>>> http://www.gwtproject.org/doc/latest/DevGuideOrganizingProjects.html#DevG
> >>>> uideHostPage [2] Dynamic string internationalisation -
> >>>> http://www.gwtproject.org/doc/latest/DevGuideI18n.html#DevGuideDynamicStr
> >>>> ingInternationalization [3]
> >>>> http://www.gwtproject.org/javadoc/latest/com/google/gwt/i18n/client/Dicti
> >>>> onary.html
> >>>>
> >>>> Thanks,
> >>>> Roy
> >>>> _______________________________________________
> >>>> Engine-devel mailing list
> >>>> Engine-devel at ovirt.org
> >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>
> >> _______________________________________________
> >> Engine-devel mailing list
> >> Engine-devel at ovirt.org
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