Overview on Apache Karaf, Pax Web, and Camel archetypes
In my previous blog post, I introduced the Karaf Maven plugins.
The Karaf Maven plugins are really helpful, starting from an existing POM.
If you can write this POM by hand (it’s my favorite way ;)), we also provide several archetypes which create and pre-configure a Maven project for you.
The next Karaf release (2.2.5) provides a set of new archetypes:
The karaf-assembly-archetype create a Maven project which create a custom Karaf distribution.
It allows you to create your own Karaf distribution. The project downloads a Karaf standard distribution (in tar.gz and zip formats), unpack it, and create a new distribution.
The easiest way to use it is to use the interactive mode:
mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-assembly-archetype -DarchetypeVersion=2.2.5-SNAPSHOT
If basically a bundle is a jar file with some special statement in the MANIFEST, the easiest way to create a bundle is to use the Felix maven-bundle-plugin.
Karaf provides an archetype which prepare a Maven project and provide a bundle Activator (a special callback class when the bundle start/stop).
To generate this project, simply type:
mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-bundle-archetype -DarchetypeVersion=2.2.5-SNAPSHOT
NB: I think that this archetype should be in Felix (as the same level as maven-bundle-plugin), I will propose a donation to the Felix community.
Blueprint is IoC approach applied to OSGi (it comes from Spring DM in fact). It allows you to avoid to write bundle Activator, ServiceTracker, etc.
Karaf provides a karaf-blueprint-archetype which prepare a Maven project including the maven-bundle-plugin, and a blueprint descriptor with a sample of OSGi service definition:
mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-blueprint-archetype -DarchetypeVersion=2.2.5-SNAPSHOT
NB: I think that this archetype should be in Aries (as it’s the blueprint implementation used in Karaf), I will propose a donation to the Aries community.
In Karaf, a feature is an application descriptor, defining all bundles, configurations/configuration files, others features. This features descriptor could be generated by hand (it’s my favorite way, and I guess the recommended one), we also provide a archetype which prepare a project to generate features file regarding the POM dependencies:
mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-feature-archetype -DarchetypeVersion=2.2.5-SNAPSHOT
We saw in my previous post a new goal of the features-maven-plugin to create a kar file starting from a features XML. A KAR file is a zip file containing the features XML and all its dependencies.
We also provide an archetype to prepare a Maven project containing a features XML and generate a KAR file:
mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-kar-archetype -DarchetypeVersion=2.2.5-SNAPSHOT
We also add several archetypes in Pax Web to deal with the web bundle. Charles talk about wab-gwt archetype in his last blog entry (http://cmoulliard.blogspot.com/2011/12/run-google-web-toolkit-2-project-on.html), but I added also two others.
Web Bundle Archetype
The Web Bundle Archetype create a “special” bundle containing web resources and statements. It creates a Maven project with webapp resources and WebApp Context in the POM:
mvn archetype:generate -DarchetypeGroupId=org.ops4j.pax.web.archetypes -DarchetypeArtifactId=wab-archetype -DarchetypeVersion=1.1.2-SNAPSHOT
We also provide an archetype to create a Maven project which generate a standard war (that you can deploy “outside” of OSGi) but including OSGi statements in the MANIFEST (which allows you to use OSGi values):
mvn archetype:generate -DarchetypeGroupId=org.ops4j.pax.web.archetypes -DarchetypeArtifactId=war-archetype -DarchetypeVersion=1.1.2-SNAPSHOT
Camel also provides a set of very useful archetypes, especially:
camel-archetype-blueprintto generate a Maven project with a blueprint XML in which you can define your routes
camel-archetype-componentproviding a template to create your own Camel component
camel-archetype-dataformatproviding a template to create your own Camel data format
camel-archetype-javaproviding a template with a class in which you can define your routes
camel-archetype-springto generate a Maven project with a Spring XML in which you can define your routes
For instance, to create a Camel blueprint Maven project, simply type:
mvn archetype:generate -DarchetypeGroupId=org.apache.camel.archetypes -DarchetypeArtifactId=camel-archetype-blueprint -DarchetypeVersion=2.9-SNAPSHOT