Re: More customizable standard GET and POST servlets (was: Json Rendering)

[Felix Meschberger <fm...@gmail.com>]

Hi,

Am Mittwoch, den 18.06.2008, 17:04 +0200 schrieb Bertrand Delacretaz:
> I agree that replacing parts of the behavior of the standard GET and
> POST servlets can be useful, but I'm not sure if this can be fully
> generalized without making things too complex.

Agreed. And we should take extreme care to find out, what exactly we are
trying to do !

> I have two use cases in mind where this would be useful:
> 
> 1) Generating different flavors of JSON output, probably based on selectors

Well, the JsonRendererServlet is fairly simple. If you need your own
rendering, just register a servlet for json rendering (or whatever
selector and/or extension you choose), copy that servlet and adapt it to
suit your needs. Done. No need to worry about OO extensibility and stuff
in this special case IMHO ...

This was really the goal behind _not_ registering the default get
servlet for specific extensions. This allows for user-supplied
better/different renderings for specific extensions.

If we go this way (and for simplicity etc. sake I would suggest to go
this way), we might want to beautify the JsonRendererServlet to make it
easier to hack up.

I think the key part behind this is, that "sling/servlet/default" is
actually an implicit root resource type just as java.lang.Object is the
root class for all Java classes. So registering something for the
"sling/servlet/default" resource type will allow you to register your
own default servlets and scripts. Documentation on this is still pending
(SLING-421 [2]).

> 2) Allowing scripts to reuse part of the POST servlet functionality,
> while customizing part of the POST request processing.

This is already possible to a certain extent: The servlets/post bundle
exports the SlingPostOperation interface and the
AbstractSlingPostOperation abstract class to make the POST servlet
extensible. Using this mechanism -- namely registering a
SlingPostOperation servlet, see the interface java doc for more info --
it is possible to extend the SlingPostServlet easily.

This is documented at [1].

If this does not suit your needs, we welcome any new use cases which we
will certainly seek to support.

Regards
Felix

[1]
http://incubator.apache.org/sling/site/manipulating-content-the-slingpostservlet.html
[2] https://issues.apache.org/jira/browse/SLING-421

> 
> I think 1) is fairly easy to solve by making the JsonRendererServlet
> more expandable, maybe simply factoring out the instantiation of the
> JsonItemWriter so that people can provide custom variants, by
> registering servlets that extend JsonRendererServlet. I think this
> "standard rendering customization" only makes sense for the JSON
> format currently, so no need for a generalized framework.
> 
> Solving 2) looks like a different problem, where the SlingPostServlet
> functionality might need to be broken down in smaller services and
> components that scripts can reuse in a modular way.
> 
> I don't see other use cases for customizing our standard servlets at
> the moment, so I feel the above two cases can be handled "locally"
> without creating a generalized (and possibly complex) customization
> framework.
> 
> -Bertrand

Re: More customizable standard GET and POST servlets (was: Json Rendering)

[Bertrand Delacretaz <bd...@apache.org>]

On Thu, Jun 19, 2008 at 11:27 AM, Christophe Lombart
<ch...@gmail.com> wrote:
> ...Maybe we can explain the possibility to override the default GET servlet
> with a script in apps/sling/servlet/default in the FAQ or in another wiki
> pages (not sure if this already done)....

I added that info yesterday at
http://cwiki.apache.org/SLING/faq.html#FAQ-Howtoreplacethedefaultjsonrenderer%2528forexample%2529withmyown%253F

-Bertrand

Re: More customizable standard GET and POST servlets (was: Json Rendering)

[Felix Meschberger <fm...@gmail.com>]

Hi,

Am Donnerstag, den 19.06.2008, 11:27 +0200 schrieb Christophe Lombart:
> >
> >
> > If this does not suit your needs, we welcome any new use cases which we
> > will certainly seek to support.
> >
> 
> 
> I'm agree with all this stuff and my use case is solved with a simple esp
> script with a selector associated to apps/sling/servlet/default. By this way
> I keep the default Json rendenring.
> 
> Maybe we can explain the possibility to override the default GET servlet
> with a script in apps/sling/servlet/default in the FAQ or in another wiki
> pages (not sure if this already done).

I think this should be documented as per SLING-421. In addition a sample
in wiki is certainly a very good idea.

Regards
Felix

Re: More customizable standard GET and POST servlets (was: Json Rendering)

[Christophe Lombart <ch...@gmail.com>]

>
>
> If this does not suit your needs, we welcome any new use cases which we
> will certainly seek to support.
>


I'm agree with all this stuff and my use case is solved with a simple esp
script with a selector associated to apps/sling/servlet/default. By this way
I keep the default Json rendenring.

Maybe we can explain the possibility to override the default GET servlet
with a script in apps/sling/servlet/default in the FAQ or in another wiki
pages (not sure if this already done).

Thanks a lot

Christophe