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and Karaf features. Karaf can also proxy other repositories and generate metadata on
the fly. It will be interesting to see how these projects mature. The Apache Felix Sigil
project provides another implementation, as well as a set of UI tools and build plug-ins.
We also expect that the Felix OBR project will update its implementation to comply with
the standard.
No matter which technology you choose, to get the most from a provisioner you
need access to a repository of bundles to provision from. Fortunately, there are a num-
ber of public repositories and repository generation tools available for you to use.
Bundle repositories
Much like the word database , the phrase bundle repository is overloaded. Database can
refer to a technology system that manages data, or to a collection of data. Similarly,
repository can refer to the technology for describing a collection of bundles, or to the
collection of bundles itself. Earlier, thinking of repository technology, we compared a
repository to a waiter in a restaurant with no menus. In its other meaning, a repository
is also like the food the restaurant has available. If he has bills to pay, the same waiter
might work in multiple restaurants, serving different menus. A single restaurant might
also employ multiple waiters, so that customers can inquire about asparagus, asperges ,
or Spargel .
So far we've been talking about repository technologies such as the standardized
OSG i repositories, OBR , and p2. But you're going to need food as well as waiters! A
number of public repositories make open source bundles available for provisioning
against, and you can also generate your own repositories for internal hosting. You'll
most likely want to take advantage of both options and use a mix of public bundle
repositories and ones specific to your project.
Public bundle repositories
Several open source projects host bundle repositories that support one or more of
the repository technologies we've discussed. If you don't need OSG i-specific metadata
for provisioning, there are also a number of public repositories and projects that
expose OSG i bundles as Maven artifacts. We'll cover these simpler repositories later in
section 12.1.1.
XML repository formats
At the time of writing, none of the repositories we'll discuss support the new standard
OSGi XML repository format. The repository specification has been under active de-
velopment for a long time, and most OBR repositories are based on a relatively old
public draft of the specification, when the specification was still called OBR! This XML
is supported by current releases of Felix OBR and other tools in Apache Aries, but
isn't up to date with the final specification.
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