Note that this code has moved to the o.a.s.servlets.resolver module - as I write this, discussions are ongoing on the Sling dev list on whether this module needs to be deprecated or repurposed.
The org.apache.sling.scripting.bundle.tracker
bundle represents an add-on module that can be deployed on a Sling 10 instance or newer to enhance the scripting resolving capabilities. Being an add-on, the bundle hooks into Sling's current mechanisms for content-to-servlet resolution and essentially acts as a service registration broker for bundles providing scripting capabilities (more details in the “How” section).
Although traditionally scripts are deployed as content stored in the search paths of a Sling instance, this leaves very little room for script evolution in a backwards compatible way. Furthermore, versioning scripts is a difficult process if the only mechanism to do this is the sling:resourceType
property, since consumers (content nodes or other resource types) have then to explicitly mention the version expected to be executed.
Scripts should not be considered content, since their only purpose is to actually generate the rendering for a certain content structure. They are not consumed by users, but rather by the Sling Engine itself and have very little meaning outside this context. As such, scripts should be handled like code:
Being built around a BundleTrackerCustomizer
[2], the Scripting Bundle Tracker monitors the instance's bundles wired to itself and scans the ones providing a sling.resourceType
capability [3]. The wiring is created by placing a Require-Capability
header in the bundles that provide the sling.resourceType
capability:
osgi.extender;filter:="(&(osgi.extender=sling.scripting)(version>=1.0.0)(!(version>=2.0.0)))"
A sling.resourceType
capability has the following attributes:
sling.resourceType:String
- mandatory; defines the provided resource type; its value is a valid Java package identifier, though it does not need to correspond to one;sling.resourceType.selectors:List
- optional; defines the list of selectors that this resource type can handle;sling.resourceType.extensions:List
- optional; defines the list of extensions that this resource type can handle;version:Version
- mandatory; defines the version of the provided resourceType
;extends:String
- optional; defines which resource type it extends; the version range of the extended resource type is defined in a Require-Capability
.The BundleTrackerCustomizer
will register a Sling Servlet with the appropriate sling.servlet
properties for each sling.resourceType
capability. The servlets will be registered using the bundle context of the bundle providing the sling.resourceType
capability, making sure to expose the different versions of a resource type as part of the registered servlet's properties. On top of this, a plain resource type bound servlet will also be registered, which will be automatically wired to the highest version of resourceType
. All the mentioned service registrations are managed automatically by the BundleTrackerCustomizer
.
Short answer: exactly like you deploy your code, preferably right next to it. Pack your scripts using the following conventions:
javax.script
folder in your bundle;javax.script
will identify a resourceType
; the folder name should preferably be a valid Java package identifier, but it does not need to refer to an existing one;resourceType
folder create a Version
folder; this has to follow the Semantic Versioning constraints described at [1];scriptingbundle-maven-plugin
to your build section and add its required properties in the maven-bundle-plugin
's instructions (check this example);mvn clean sling:install
.The integration tests are provided by the org.apache.sling.scripting.bundle.tracker.it
project. To run the integration tests execute the following command:
mvn clean verify -Pit
To play around with a Sling instance on localhost port 8080 (override with -Dhttp.port=) that has the examples installed run:
mvn clean verify -Pexample
from the org.apache.sling.scripting.bundle.tracker.it
project.
[1] - https://semver.org/
[2] - https://osgi.org/javadoc/r6/core/org/osgi/util/tracker/BundleTrackerCustomizer.html
[3] - https://osgi.org/download/r6/osgi.core-6.0.0.pdf, Page 41, section 3.3.3 “Bundle Capabilities”
[4] - https://sling.apache.org/documentation/the-sling-engine/url-to-script-resolution.html