Choosing a stack - Enterprise OSGi in Action

Java Reference

In-Depth Information

Maven URL s were used for convenience here, but file and http URL s also work. The

feature definition file for the Fancy Foods application would be as follows:

<bundle>mvn:fancyfoods/fancyfoods.api/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.web/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.business/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.datasource/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.persistence/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.department.chocolate/1.0.0</bundle>

<bundle>mvn:fancyfoods/fancyfoods.department.cheese/1.0.0</bundle>

</feature>

</features>

It's used here because the content is familiar, but the Fancy Foods application perhaps

isn't the best example of how to use Karaf features. A similar effect can be achieved by

packaging all of the Fancy Foods bundles up into a .eba file, as we did in chapter 4.

Features are more useful for distributing centrally—or remotely—managed infra-

structure bundles. For example, many Apache projects provide Karaf feature files to

allow them to be installed into Karaf without any initial download.

If you try to install it, you'll discover that the Fancy Foods application won't install

correctly on a basic Karaf installation because its dependencies are missing; current

releases of Karaf don't have any ability to provision features based on bundle depen-

dencies. Don't worry, we'll show you how to configure Karaf with the right features in

a moment.

13.2.2

Installing Aries into Karaf

Despite being a relatively lightweight runtime, Karaf has awareness of, and support

for, Aries. Base Karaf ships with the Aries Blueprint implementation. Although not

installed by default, the Karaf enterprise repository includes feature definitions for

most Aries components. The feature definitions are maintained by the Karaf team

and so versions may lag slightly behind the latest Aries releases (see figure 13.2).

WARNING: BUT WHERE IS THE ARIES FEATURE? None of the Karaf feature defi-

nitions for the Aries bundles includes aries in the name, so they're easy to miss

if you're looking for a feature called aries .

Unfortunately, although there are Karaf feature files for the Aries JPA component,

which provides integrations for JPA in an OSG i environment, at the time of writing

there are none for the Open JPA engine itself. You'll need to install Open JPA into

Karaf manually, either by using the bundles:install command or by writing your

own feature for Open JPA . Because Open JPA has its own nontrivial dependencies, a

feature is probably easier. An example feature definition is as follows:

<feature

name="persistence"

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