Hi all
I had various discussions around execution of Servlet API Filters in the Sling
Engine.
To recap: Currently all filters are always called. The service.ranking (or
filter.order) service registration property can be used to define the order in
which the filters are called and the filter.scope property is required to
indicate at what stage in the request processing a filter has to be called. See
[1] for the full story.
Turns out, that it would be good to have some simple and global flags to
indicate when a filter should actually be called or not. This would be similar
to the filter mappings of traditional web applications, where filters are bound
to URL paths and/or servlets.
So I am proposing to introduce three new service registration properties, which
may be set on Servlet Filter services handled by the Sling Engine:
* filter.path: The Filter is only called if the path of the
current Resource (SlingHttpServletRequest.getResource)
matches any of the given paths. If the property is
not set, the filter will always be called.
* filter.resourceType: The Filter is only called if the resourceType
of the current Resource (SlingHttpServletRequest.getResource)
matches any of the given resource types. If the property is
not set, the filter will always be called.
* filter.ignore: The Filter is never called if this property
is set to any "true".
The implementation would be as follows:
* The FilterListEntry class is augmented with a method to verify whether to
call the filter at all
* The AbstractSlingFilterChain.doFilter method is augmented to call this new
method and to not call a filter for which the match fails. A
RequestProgressTracker entry is generated for filters not called indicating why
it has not been called.
Further extensions could be:
* filter.expression: some scripting expression evaluating to
a boolean. If true the filter is called.
* Filter service implements a new interface providing an filter
expression method returning a boolean. If true the filter
is called (comparable to the option servlet).
Regards
Felix
[1] http://sling.apache.org/documentation/the-sling-engine/filters.html
