Hi all,
I started working on a prototype for the API Region support for the Sling
Feature model as outlined in [1]. The prototype includes runtime support
for enforcing the API Regions as declared in the feature model files. This
mail is to share my current approach, which is partly implemented on my
branch (features-service) and in the sling-whiteboard.
An API region is specified in a feature file using an extension. For
example:
"api-regions:JSON|false" : [
{
"name": "platform",
"exports": [
"org.apache.sling.commons.scheduler"
]
}
]
This means that the org.apache.sling.commons.scheduler package from a
bundle in this feature is exposed outside of the feature in the 'platform'
region. It means that other features also in the 'platform' region have
access to it, but features not in the 'platform' region don't. Within a
single feature all bundles have access to all exported package from other
bundles in the same region.
To realise this at runtime, I created a WhitelistEnforcer component which
knows of the whitelist configuration at runtime. The Feature launcher will
initialize this component with the api region information. The
WhitelistEnforcer registers a framework resolver hook which can prevent
bundles from resolving to API from other bundles if this API should not be
exposed to the requesting bundle.
Additionally, I created a Features service, which can at runtime tell the
caller what feature a given bundle belongs to. The OSGi resolver hook only
tells you whether a given bundle needs something, so in order to map that
to the api-regions configuration which is defined on the feature level, we
need to know what feature this bundle belongs to.
Both the WhitelistEnforcer as well as the Features service are defined by
framework extension fragment bundles so that they are present early in the
system.
There is also an associated JIRA:
https://issues.apache.org/jira/browse/SLING-7779
I'm hoping to merge this soon to the Sling codebase, any thoughts would be
appreciated :)
Best regards,
David
[1]
https://github.com/apache/sling-org-apache-sling-feature/blob/master/apicontroller.md
