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From Apache Wiki <wikidi...@apache.org>
Subject [Jackrabbit Wiki] Update of "ApacheSling/SlingInitialStartup" by FelixMeschberger
Date Thu, 05 Jul 2007 11:52:28 GMT
Dear Wiki user,

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

The following page has been changed by FelixMeschberger:
http://wiki.apache.org/jackrabbit/ApacheSling/SlingInitialStartup

The comment on the change is:
Creation

New page:
= Initial Provisioning and Startup =


== We got a Launch ==

The most complicated tasks getting Sling or any Sling application up and running is launching
the framework and providing the initial installation. To simplify these tasks, great efforts
have been taken. The result is a Standalone Java Application - the Sling App - and a Web Application
- the Sling Servlet - with embedded libraries and a core set of bundles and a mechanism to
provide initial configuration and installation. The following description applies to both
the standalone application and the web application.

When Sling is first started the following steps are executed:

   * The initial configuration is loaded as described in the [:../SlingConfiguration#Initial_Configuration:here].
   * The list of bundles embedded in the application is set to the {{{felix.autostart.1}}}
property. This will automatically install and start these bundles in start level 1. Currently
this list is hard coded and consists of the following bundles:
      * {{{org.apache.sling.sling-log}}} - The OSGi Log Service implementation of Project
Sling also exporting logging APIs
      * {{{org.apache.sling.sling-assembly}}} - Installation and Update Management support
      * {{{org.apache.felix.bundlerepository}}} - Apache Felix implementation of the OSGi
Bundle Repository specification.
   * The Apache Felix framework is launched and an URL handler for the {{{context:}}} scheme
is registered to provide access to the contents of the Sling Web Application.
   * As soon as the Framework has been started, the {{{com.day.sling.assembly}}} bundle inspects
the Framework properties available through the {{{BundleContext.getProperty(String)}}} method
to install bundles from configured OSGi Bundle Repositories.



== Initial Bundle Installation by the sling-assembly Bundle ==

When the ''sling-assembly'' bundle is started it registers a {{{FrameworkEventListener}}}
which justs listens for the {{{FRAMEWORK_STARTED}}} event. When this event comes in, the framework
is up and running, the ''sling-assembly'' bundle will look at the Framework properties to
see, whether any bundles need to be installed. This is done along the lines of the following
pseudo code:

{{{String startLevelList = bundleContext.getProperty( "sling.install.bundles" )
for ( each startLevel in startLevelList ) do
    String bundleList = bundleContext.getProperty( "sling.install." + startLevel )
    for ( each bundle in bundleList )  do
        if ( not isInstalled( bundle ) ) then
            install( bundle )
            setStartLevel( bundle, startLevel )
        fi
    done
done

for ( each bundle installed ) do
    start( bundle )
done}}}


=== Example ===

Given the following properties

{{{sling.install.bundles = 1, 10, 20
sling.install.1 = org.apache.sling.assemblies.osgi-compendium-assembly:0.1.0, \
 org.apache.sling.assemblies.sling-console-web-assembly:0.1.0
sling.install.10 = org.apache.sling.assemblies.sling-crx-server-assembly:[1,2)
sling.install.20 = org.apache.sling.assemblies.sling-assembly}}}


These bundles will be installed:

|| '''Bundle''' || '''Version''' || '''Start Level''' ||
|| {{{org.apache.sling.assemblies.osgi-compendium-assembly}}} || >= 0.1.0 || 1 ||
|| {{{org.apache.sling.assemblies.sling-console-web-assembly}}} || >= 0.1.0 || 1 ||
|| {{{org.apache.sling.assemblies.sling-crx-server-assembly}}} || Any Version with Major Version
1 || 10 ||
|| {{{org.apache.sling.assemblies.sling-assembly}}} || Any Version || 20 ||


'''Notes'''

   1. The Sling application takes care of constructing the {{{sling.install.bundles}}} property
from the {{{sling.install.<n>}}} properties found from the different property sources
loaded before launching the framework. The {{{sling.install.bundles}}} property needs only
be manually created in case the Sling Servlet is not used to launch the OSGi framework for
Sling.
   1. Any {{{sling.install.<n>}}} property whose start level value {{{<n>}}} is
not listed in the {{{sling.install.bundles}}} property is ignored.
   1. The {{{sling.install.<n>}}} properties are comma-separated lists of bundle specifications
where each entry is a tuple of a bundle symbolic name and an optional version range specification
(see section 3.2.5, Version Ranges, in the OSGi Service Platform Core Specification). If no
version range (or single version) is specified for an entry, any version is applicable.
   1. The bundles listed in the {{{sling.install.<n>}}} properties are simple bundles
from the point of view of initial installation. If any of the bundles happen to be an Assembly
Bundle (see [:../SlingAssembly:Assembly: Bundling Bundles]) the Assembly Manager will take
care of that bundle after the bundle has been installed.



== Important Properties ==

To recapitulate here is a list of Framework properties used for initial provisioning:

|| '''Property''' || '''Description''' ||
|| {{{obr.repository.url}}} || A comma-separated list of OSGi Bundle Repository URLs. This
property is required to access the OSGi Bundle Repository to install the bundles listed in
the {{{sling.install.<n>}}} properties. See the {{{org.apache.felix.bundlerepository}}}
Bundle documentation for more information on this property. ||
|| {{{sling.install.bundles}}} || A comma-separated list of start level numbers referring
to {{{sling.install.<n>}}} properties listing bundles to install. If this property is
empty or  missing, nothing will be installed. ||
|| {{{sling.install.<n>}}} || A comma-separated list of bundle specifications consisting
of the (required) bundle symbolic name and an (optional) version range specification separated
by colon. Any {{{sling.install.<n>}}} property whose start level value {{{<n>}}}
is not listed in the {{{sling.install.bundles}}}, property is ignored. ||



== Using the Sling Standalone Application ==

The Sling Standalone Application is available as an executable JAR file and may be started
by just specifying a simple command line:

{{{
java -jar sling-app.jar
}}}

This causes Sling to start up as described above. The configuration built into the Sling Standalone
Application causes the Apache Felix ''http.jetty'' bundle to be installed to run an embedded
Servlet Container backing the OSGi HTTPService implementation used to provide the Sling Management
Console.



== Using the Sling Web Application ==

Launching Sling in a servlet container is equally simple as using the standalone application:
Grab the ''sling-servlet'' web application and deploy it into your favourite servlet container.

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