Google Git
Sign in
apache / sling-whiteboard / refs/heads/cms-fileoptim-support / . / scripting-resolver
tree: 1cce92713ed41ef6d095177ad66f6d463a79fecb [path history] [tgz]
  1. examples/
  2. org-apache-sling-scripting-maven-plugin/
  3. org-apache-sling-scripting-resolver/
  4. .gitignore
  5. pom.xml
  6. README.md
scripting-resolver/README.md

Apache Sling Scripting Reloaded Build Status

Overview

Apache Sling embraced David's Model [1] when it was designed, therefore everything is content, including rendering scripts. While this mechanism makes script deployment an easy task, it leads to several disadvantages:

  • scripts are directly accessible by platform users, if they have read permissions for the search paths, although scripts should have a developer-only audience
  • scripts can be overlaid freely through the search path override or through the special sling:resourceSuperType property, complicating a developer's understanding of the script resolution mechanism
  • changing a previously available script in an application can pose backwards compatibility and upgrade issues that the developers have to handle through various workarounds (e.g. path-based versioning)

The only way to overcome the stated disadvantages is to redesign the way scripting works:

  • component scripts should be deployed through bundles, exactly like Java code;
  • component scripts should should be organised into semantically versioned packages, with clear definitions for what constitutes:
    • a micro change
    • a minor change
    • a major change
  • a bundle providing scripts should explicitly declare the feature(s) (resource types), by making use of theProvide-Capability [2] header;
  • a bundle providing scripts that extend an existing feature (resource type) should declare this intention explicitly:
    • by employing the Require-Capability [2] header, to reference the feature the bundle extends
    • a Provide-Capability header should describe the new feature (resource type), obtained by extending

Advantages of the new design:

  • the Require / Provide explicit mechanism removes the need for search paths and also for the sling:resourceSuperType mechanism, transforming script resolution essentially into a Map built at deploy time;
  • backwards compatibility will be handled the same way we do for Java APIs, allowing for smoother upgrades and delivery of new features
  • such a model could be described through Apache Sling's Feature Model [3], allowing an application to be built using a mix & match technique for collecting the components it requires for rendering.

Further reading

For a detailed view of how this project works please check each module's documentations plus the provided examples.

References

[1] - https://wiki.apache.org/jackrabbit/DavidsModel
[2] - https://osgi.org/download/r6/osgi.core-6.0.0.pdf, Page 41, section 3.3.3 “Bundle Capabilities”
[3] - https://github.com/apache/sling-org-apache-sling-feature