Use Bundle Extender Pattern to allow Bundles to expose Resource to the
DataFileProvider
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Key: STANBOL-234
URL: https://issues.apache.org/jira/browse/STANBOL-234
Project: Stanbol
Issue Type: New Feature
Components: Commons
Reporter: Rupert Westenthaler
Assignee: Rupert Westenthaler
If a bundle contains the "Data-Files" header field the values are interpreted
as paths within the Bundle that contain data files. Multiple paths can be
defined by using ',' as separator.
A BundleListerner keeps track of all active Bundles with this header and
registers a DataFileProvider for the configured paths. By this data files
contained by a Bundle are available via the main DataFileProvider.
In addition the "Data-Files-Priority" header may by used to define the service
ranking for the DataFileProvider created and registered for this bundle.
Bundles that provide default data should use a negative value to ensure that
they get overridden by Bundles that do not define this property. Bundles that
need to override preexisting data files should use positive values. Note that
the main DataFileProvider (loading files form the /datafiles folder) uses
Integer.MAX_VALUE as ranking.
Creating such Bundles can be done by adding
"<Data-Files>{path1},{path2}</Data-Files>" to the instructions of the
maven-bundle-plugin
The first place to use this will be the "org.apache.stanbol.defaultdata" bundle
that provides the minimal set of data needed for the configuration shipped with
different launchers. Currently it contains the statistical model for OpenNLP.
Current Situation
* The path to the files needs to be hard coded in all bundles using this models
(currently the opennlp-ner enhancement engine)
* An own Classpath based DataFileProvider must be implemented and registered as
Service to allow loading that resources via the classpath (while still using
the DataFileProvider
* Because the DataFileProvider is used additional files can be provided by
copying Files to the /datafiles folder
By using the proposed Bundle DataFileProvider
* A component may define a dependency to the Bundle containing the required
data. This ensures that required data are available.
* The component must not do anything to get access to the data, because the
required DataFileProvider for the Bundle is initialized automatically.
* Default Data can be overridden by specifying the "Data-Files-Priority" header
for a Bundle.
* Additional data can be made available automatically by adding an other Bundle
with the "Data-Files" header or by directly copying Files to the /datafiles
folder
For more Information on the Bundle Extender Pattern see
http://www.aqute.biz/Snippets/Extender
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