This is an automated email from the ASF dual-hosted git repository.
cziegeler pushed a commit to branch master
in repository
https://gitbox.apache.org/repos/asf/sling-org-apache-sling-feature-extension-apiregions.git
The following commit(s) were added to refs/heads/master by this push:
new e264d9f Move api region documentation to extension
e264d9f is described below
commit e264d9f055d1fe780811c52ae98c6b32c5cc9587
Author: Carsten Ziegeler <[email protected]>
AuthorDate: Fri Mar 27 07:26:35 2020 +0100
Move api region documentation to extension
---
README.md | 16 ++++++-------
docs/api-regions.md | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+), 8 deletions(-)
diff --git a/README.md b/README.md
index bd06f86..188c987 100644
--- a/README.md
+++ b/README.md
@@ -4,8 +4,8 @@
# Apache Sling API Regions extension
-This component contains extensions relating to the API Regions component. For
more information about API Regions see
-https://github.com/apache/sling-org-apache-sling-feature/blob/master/apicontroller.md
+This component contains extensions relating to the API Regions component.
+Read the documentation about [API Regions](docs/api-regions.md) for more
information.
The following extensions are registered via the ServiceLoader mechanism:
@@ -18,7 +18,7 @@ Merge handlers are called when features are merged during the
aggregation proces
This component also contains Feature Model Analysers they are contributed
through the Service Loader mechanism to the set of Analysers.
-These analysers relate to API Region definitions in Feature Models.
+These analysers relate to API Region definitions in Feature Models.
* `api-regions`: This analyser ensures that packages listed as exports in
API-Regions sections are actually exported by a bundle that's part of the
feature.
@@ -26,12 +26,12 @@ These analysers relate to API Region definitions in Feature
Models.
* Configuration parameters:
* `exporting-apis`: the name of the region that provides the visible APIs.
* `hiding-apis`: the name of the region that is 'hidden' i.e. not as visible
as the exporting one. The
-packages in the `exporting-api` cannot depend on any packages from this
region.
+packages in the `exporting-api` cannot depend on any packages from this region.
* `api-regions-duplicates`: This analyser ensures that packages are only
listed in one region
in a given feature. If the same package is listed in multiple regions this
will be an error.
-* `api-regions-check-order`: This analyser checks that regions are defined in
the specified
+* `api-regions-check-order`: This analyser checks that regions are defined in
the specified
order and that the same region is only declared once. Later regions inherit
the packages
expose in earlier regions in the list, so the order is important.
* Configuration parameters:
@@ -41,9 +41,9 @@ order must be obeyed.
* `api-regions-crossfeature-dups`: This analyser checks whether there are
exported packages in a feature model
that does _not_ opt in to the API Regions (i.e. it does not have an
API-Regions section) that overlap with exported
packages from API regions in other feature models. It can prevent against
unwanted results when packages are
-exported from the outside which should be exported from an API Region.
-This analyser only provides a useful result when run on
-an aggregate feature model, i.e. a feature model that was created by
aggregating a number of other feature models. It uses the
+exported from the outside which should be exported from an API Region.
+This analyser only provides a useful result when run on
+an aggregate feature model, i.e. a feature model that was created by
aggregating a number of other feature models. It uses the
`feature-origins` metadata to find the features that bundles were initially
declared in. It then matches this with the `feature-origins` found in the
`api-regions` section. Exports from bundles from features that don't
declare `api-regions` are compared to declared exports in the `api-regions`
section. If there is overlap an error
is reported.
diff --git a/docs/api-regions.md b/docs/api-regions.md
new file mode 100644
index 0000000..412d8ea
--- /dev/null
+++ b/docs/api-regions.md
@@ -0,0 +1,66 @@
+# API Regions
+
+If you're assembling a platform (in contrast to a final application) out of
several features and provide this platform for customers to build their
application on top of, additional control of the API provided by the platform
is needed. The bundles within the features provide all kinds of APIs but you
might not want to expose all of these as extension points. You would rather
want to use some of them internally within either a single feature or share
within your platform features.
+
+# Visibility of API
+
+A feature exports some api, however there are different types of clients of
the API:
+
+* Bundles shipped as part of the platform
+* Application bundles using the platform
+
+We can generalize this by saying that API is either globally visible (to every
client) or only visible to features within the same context. Usually this is
referred to as a "region": The platform spawns its own region and a customer
application has its own region, too. In theory there could be several customer
applications running in the same framework on top of the platform, and each
application has its own region.
+
+Without any further information, API is globally visible by default. However,
for platform features we want the opposite as we want to ensure that newly
added API is not visible to all bundles by default.
+
+A feature can have an additional extension JSON named api-regions. The
following example exposes some packages to the global region and an additional
package to the platform region. Exports declared earlier in the api-regions
array also apply to later elements in the array, so the `platform` region also
contains all exports declared for the `global` region.
+
+Note that the `global` region is a predefined region that exports the listed
packages to everyone. Other region names can be chosen freely. Packages listed
in these other regions are only exposed to bundles in features that are in the
same region.
+
+ "api-regions:JSON|optinal" : [
+ {
+ "name": "global",
+ "exports": [
+ "# Export Sling's resource API in the global region",
+ "org.apache.sling.resource.api",
+ "org.apache.sling.resource.api.adapter",
+ "org.apache.sling.resource.api.auth",
+ "org.apache.sling.resource.api.request",
+ "org.apache.sling.resource.api.resource"
+ ]
+ },{
+ "name": "platform",
+ "exports": [
+ "# Export the scheduler API in the platform region.",
+ "# All exports in earlier regions defined here also apply.",
+ "org.apache.sling.commons.scheduler"
+ ]
+ }
+ ]
+
+Of course the above mentioned packages need to be exported by some bundle
within the feature.
+By exporting packages to a given region, a feature automatically also sees all
packages available to that region (or regions).
+
+A feature can also just consume packages from a region, without having to
export any packages to it. This can be done by exporting an empty list of
packages. For example:
+
+ "api-regions:JSON|optional" : [
+ {
+ "name": "platform",
+ "exports": []
+ }
+ ]
+
+If the api-regions extension is missing or the api-regions information is
missing, it is assumed that all packages are exported to the "global" region
and all packages in the global region are visible to the feature.
+
+If a feature exports no packages and only wants to have visibility of packages
from the global region, this can be specified as follows:
+
+ "api-regions:JSON|optional" : [
+ {
+ "name": "global",
+ "exports": []
+ }
+ ]
+
+To support feature inheritance, [this module](../README.md) containing an
extension handler must be registered which will merge the extension.
+
+A number of API region related analysers/validators exist. Documentation can
be found here:
https://github.com/apache/sling-org-apache-sling-feature-analyser . These can
be run as part of the 'analyse-features' goal with the
[slingfeature-maven-plugin](https://github.com/apache/sling-slingfeature-maven-plugin#analyse-features-analyse-features).
