Mailing-List: contact commits-help@jackrabbit.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@jackrabbit.apache.org
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Fri, 29 Jan 2010 10:20:19 -0000
Message-ID: <20100129102019.14206.55668@eos.apache.org>
Subject: 
 =?utf-8?q?=5BJackrabbit_Wiki=5D_Update_of_=22JackrabbitOsgi=22_by_FelixMe?=
 =?utf-8?q?schberger?=

Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Jackrabbit Wiki" fo=
r change notification.

The "JackrabbitOsgi" page has been changed by FelixMeschberger.
http://wiki.apache.org/jackrabbit/JackrabbitOsgi?action=3Ddiff&rev1=3D1&rev=
2=3D2

--------------------------------------------------

  =3D Embedding A Jackrabbit Repository in an OSGi Framework =3D
  The Apache Sling project has provided an infrastructure for embedding and=
 accessing JCR Repositories right from the start. With Jackrabbit 2 it is a=
bout time, that Jackrabbit itself becomes more OSGi friendly and provides m=
any of the features which are currently part of Apache Sling.
  =

- This page is about the changes and enhancements proposed in the [[http://=
svn.apache.org/repos/asf/jackrabbit/sandbox/jackrabbit2-bundle][Jackrabbit =
2 Bundle Sandbox]].
+ This page is about the changes and enhancements proposed in the [[http://=
svn.apache.org/repos/asf/jackrabbit/sandbox/jackrabbit2-bundle|Jackrabbit 2=
 Bundle Sandbox]].
  =

  =3D=3D Apache Sling JCR Bundles =3D=3D
  Apache Sling currently provides the following JCR related bundles:
  =

  Bundle Current Version Jackrabbit Version Description
+ || '''Bundle''' || '''Current Version''' || '''Jackrabbit Version''' || '=
''Description''' ||
- =

- ||<tablestyle=3D"width: 957px; height: 116px;">Bundle||Current Version||J=
ackrabbit Version||Description||
- =

- ||<tablestyle=3D"width: 957px; height: 116px;">Sling JCR API||2.0.6||--||=
Provides additional API to simplify use. Most notably contains the SlingRep=
ository interface to ease configuration pain for bundles requiring administ=
rative repository access. This bundle used to include and provide the JCR 1=
.0 API in the OSGi framework. This has been removed to allow the provision =
of the JCR 2.0 API as a proper bundle. ||
+ ||Sling JCR API ||2.0.6 ||-- ||Provides additional API to simplify use. M=
ost notably contains the SlingRepository interface to ease configuration pa=
in for bundles requiring administrative repository access. This bundle used=
 to include and provide the JCR 1.0 API in the OSGi framework. This has bee=
n removed to allow the provision of the JCR 2.0 API as a proper bundle. ||
- ||Sling JCR Base||2.0.4||1.5||Provides an abstract default implementation=
 of the SlingRepository interface and includes the Jackrabbit RMI library a=
t version 1.5 to access a repository over RMI. This abstract base implement=
ation supports accessing repositories both through JNDI and RMI.||
+ ||Sling JCR Base ||2.0.4 ||1.5 ||Provides an abstract default implementat=
ion of the SlingRepository interface and includes the Jackrabbit RMI librar=
y at version 1.5 to access a repository over RMI. This abstract base implem=
entation supports accessing repositories both through JNDI and RMI. ||
- ||Sling JCR Classloader||3.0|| ||Provides support to load classes from th=
e repository. This bundle was based on the Jackrabbit Repository Classloade=
r. Now it contains a stripped-down copy of the class loader with a few fixe=
s.||
+ ||Sling JCR Classloader ||3.0 || ||Provides support to load classes from =
the repository. This bundle was based on the Jackrabbit Repository Classloa=
der. Now it contains a stripped-down copy of the class loader with a few fi=
xes. ||
- ||Sling Jackrabbit Client||2.0.2|| ||A concrete extension of the Abstract=
SlingRepository in the Sling JCR Base bundle. This extension is almost empt=
y, since the basic support is already provided by the abstract class.||
+ ||Sling Jackrabbit Client ||2.0.2 || ||A concrete extension of the Abstra=
ctSlingRepository in the Sling JCR Base bundle. This extension is almost em=
pty, since the basic support is already provided by the abstract class. ||
- ||Sling Jackrabbit Server||2.0.4||1.6||Embeds Jackrabbit Core and most of=
 its dependencies like Lucene, Derby, PDFBox, etc.||
+ ||Sling Jackrabbit Server ||2.0.4 ||1.6 ||Embeds Jackrabbit Core and most=
 of its dependencies like Lucene, Derby, PDFBox, etc. ||
- ||Sling Jackrabbit Access Manager||2.0.2||1.6||Supports Access Control Ma=
nagement in a Jackrabbit Repository using the Sling Features.||
+ ||Sling Jackrabbit Access Manager ||2.0.2 ||1.6 ||Supports Access Control=
 Management in a Jackrabbit Repository using the Sling Features. ||
- ||Sling Jackrabbit User Manager||2.0.2||1.6||Supports User Management in =
a Jackrabbit Repository using the Sling features.||
+ ||Sling Jackrabbit User Manager ||2.0.2 ||1.6 ||Supports User Management =
in a Jackrabbit Repository using the Sling features. ||
  =

  =

  Note: The future of the Jackrabbit Repository Classloader library has not=
 yet been decided upon. At the moment, we have a relatively stable release =
in the Commons subproject and Apache Sling has a stripped-down fork of that=
 class loader. It will have to be discussed where we are heading with this =
beast and what the requirements of the Community will be around this.
  =

  Of these bundles, the ''Sling Jackrabbit Server'' bundle is probably the =
one which should be integrated in the Jackrabbit Core library. Over time I =
could imagine to also merge most of the ''Sling JCR Base'' and ''Sling JCR =
Client'' bundles into the Jackrabbit project.
  =

+ =

+ =3D=3D Current State of OSGi Support in Jackrabbit =3D=3D
+ =

+ Currently many helper libraries of Jackrabbit are already setup as proper=
 OSGi bundles. Most notably this includes the Jackrabbit API, JCR Commons, =
SPI, and SPI Commons libraries.
+ =

+ The major missing link is the Jackrabbit Core library, which is the actua=
l implementation of the repository.
+ =

+ =

+ =3D=3D Extensions to Jackrabbit Core =3D=3D
+ =

+ The goal of turning the Jackrabbit Core library into an OSGi bundle is to=
 preserve as much of the functionality of the current Sling Jackrabbit Serv=
er bundle as possible. Concretely this means:
+ =

+   * Build the Jackrabbit Core library as a bundle (obviously)
+   * Embed only as much dependencies as are really needed (goal: none)
+   * Support easy startup and access to the embedded repository instances
+   * Provide some degree of dynamic extensibility (at least provide the pl=
uggability currently supported by the Sling Jackrabbit Server bundle)
+ =

+ =

+ =3D=3D=3D Jackrabbit Core Bundle and Embedded Dependencies =3D=3D=3D
+ =

+ The biggest issue when bundelizing the Jackrabbit Core bundle is the is t=
he list of dependencies and extensibility. =

+ =

+ The problem with dependencies is, that Jackrabbit Core has quite big numb=
er of dependencies. To launch a Jackrabbit repository a number of libraries=
 have been collected and put together. Some of these libraries are availabl=
e as OSGi bundles (e.g. the Jackrabbit helper libraries, the JCR 2.0 API, D=
erby) and some are not (yet) (e.g. Lucene, Concurrent, Commons Pool, Common=
s DBCP). Tika is special in that it will be available as a bundle starting =
with release 0.6.
+ =

+ The problem with extensibility is, that Jackrabbit Core has not been buil=
t with the kind of modularity in mind as provided by OSGi. This means inter=
nal extension API is not properly separated from internal implementations. =
This makes it close to impossible to expose the API as OSGi {{{Export-Packa=
ge}}} without also requiring to exposing internal packages.
+ =

+ The current approach followed in the [[http://svn.apache.org/repos/asf/ja=
ckrabbit/sandbox/jackrabbit2-bundle|Jackrabbit 2 Bundle Sandbox]] is to emb=
ed libraries, which are not available as bundles and to not embed libraries=
 available as bundles.
+ =

+ =

+ =3D=3D=3D Easy Startup and Access =3D=3D=3D
+ =

+ For easy startup and access the OSGi specification offers great functiona=
lities: To startup an embedded repository instance, we need a location to s=
tore the filesystem data to and a location to access a configuration. Both =
properties can easily be provided through the OSGi Configuration Admin Serv=
ice. This is what we do in the Sling Jackrabbit Server bundle and thus this=
 is also implemented in the current approach.
+ =

+ Accessing an embedded repository is equally easy: As soon as a repository=
 has been configured and started, it will be registered as an OSGi service =
and can be referenced like any other service using the service name. An emb=
edded Jackrabbit Repository is registered under the two names implemented b=
y Jackrabbit Core: {{{javax.jcr.Jackrabbit}}} and {{{org.apache.jackrabbit.=
api.JackrabbitRepository}}}.
+ =

+ The Jackrabbit Core bundle also contains an OSGi {{{BundleActivator}}} wh=
ich ensures configuration can be provided by the Configuration Admin Servic=
e and which also ensures an initial configuration to have a running reposit=
ory as soon as the bundle is started.
+ =

+ As for the configuration file: The Jackrabbit Core library contains a def=
ault repository.xml file ({{{OSGI-INF/repository_osgi.xml}}}) which is used=
 as a configuration file if none is provided.
+ =

+ =

+ =3D=3D=3D Extensibility =3D=3D=3D
+ =

+ =

+ Jackrabbit configuration is the subject of a book of its own. Yet some th=
ings may be setup rather dynamically in the sense of extensible at runtime =
by the system administrator. Things in this area, we have at the moment in =
the Sling Jackrabbit Server bundle are a framework to extend login modules =
and a support to plugin extensible access controllers.
+ =

+ Both should, if possible, be migrated to the Jackrabbit Core bundle; poss=
ibly even enhancing it. Of course such extensibility points will have to be=
 exported from the Jackrabbit Core bundle and as such will be placed into s=
eparate locations.
+=20