Changing Sling Filter support

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

Hi all,

Currently all javax.servlet.Filter services registered in the OSGi
framework is picked up by Sling (the SlingMainServlet) an added to the
Sling filter chains.

This is problematic in general and in special with respect to the
planned addition of white board support for real servlet container
filters (SLING-1223 [1]).

Incidentally we are also considering an extension to the Sling filter
support adding more filter scope values: SLING-1213 [2].

So I would like to propose the following:

  * Sling is modified to only pick Filter services which have a
    specific registration property set (say filter.scope or rather
    a new property such as sling.filter.scope or
    sling.filter.dispatcher). Likewise the current filter.order
    property should be dropped and be replaced by the standard
    OSGi service.ranking property.

  * The intended whiteboard support (SLING-1223) also is based on
    prerequisite properties (see [3]) and will only pick up filters
    with the correct properties set.

  * For backwards compatibility Sling still picks up all filters
    but ignores those which contain any of the known white board
    filter properties.

WDYT ?

Regards
Felix

[1] https://issues.apache.org/jira/browse/SLING-1223
[2] https://issues.apache.org/jira/browse/SLING-1213
[3]
http://felix.apache.org/site/apache-felix-http-service.html#ApacheFelixHttpService-UsingtheWhiteboard

Re: Changing Sling Filter support

[Carsten Ziegeler <cz...@apache.org>]

Felix Meschberger wrote:
> Hi all,
> 
> Currently all javax.servlet.Filter services registered in the OSGi
> framework is picked up by Sling (the SlingMainServlet) an added to the
> Sling filter chains.
> 
> This is problematic in general and in special with respect to the
> planned addition of white board support for real servlet container
> filters (SLING-1223 [1]).
> 
> Incidentally we are also considering an extension to the Sling filter
> support adding more filter scope values: SLING-1213 [2].
> 
> So I would like to propose the following:
> 
>   * Sling is modified to only pick Filter services which have a
>     specific registration property set (say filter.scope or rather
>     a new property such as sling.filter.scope or
>     sling.filter.dispatcher). Likewise the current filter.order
>     property should be dropped and be replaced by the standard
>     OSGi service.ranking property.
Sounds good, I would go with sling.* for the property names to avoid
possible conflicts with other stuff. And using the service ranking
instead of the order property makes sense.

>   * The intended whiteboard support (SLING-1223) also is based on
>     prerequisite properties (see [3]) and will only pick up filters
>     with the correct properties set.
> 
>   * For backwards compatibility Sling still picks up all filters
>     but ignores those which contain any of the known white board
>     filter properties.
Yepp, this is the problematim part as we somehow have to maintain
compatibilty. We should log a big warning so people start changing their
stuff to the new properties.

> 
> WDYT ?
+1

Carsten
> 
> Regards
> Felix
> 
> [1] https://issues.apache.org/jira/browse/SLING-1223
> [2] https://issues.apache.org/jira/browse/SLING-1213
> [3]
> http://felix.apache.org/site/apache-felix-http-service.html#ApacheFelixHttpService-UsingtheWhiteboard
> 


-- 
Carsten Ziegeler
cziegeler@apache.org