Enterprise OSGi Runtimes and Tooling
It was great to see several enterprise OSGi runtimes in action at EclipseCon.
Readers of this blog will be familiar with Eclipse Virgo, so suffice to say that tutorials covered developing applications using Eclipse Gemini components (reference implementations of several OSGi Enterprise standards) in Virgo and configuring and managing web applications in Virgo.
Several of the tutorials developed Web Application Bundles, or WABs, which are part of the OSGi Enterprise standard. A Web Application Bundle is like a WAR file which specifies the web context path in its manifest and which obtains its dependencies using OSGi instead of having to include them all in WEB-INF/lib. The tutorials also implemented persistence using the OSGi Enterprise standard mapping of Java Persistence API (JPA).
Apache Aries provides a collection of components including implementations of several Enterprise OSGi standards and an application model similar to Virgo's. The EclipseCon tutorial had us creating a blogging application using the free IBM® Rational® tooling. The application consisted of an Aries application containing a plain OSGi bundle, a bundle utilising JPA persistence, and a WAB. The JPA bundle used Aries extensions to the standard blueprint service. The WAB used JNDI to look up the service published by the persistence bundle - the same approach that was taken in the Gemini and Virgo tutorial. We then deployed the application to a target platform which included Aries bundles.
Apache Karaf is similar in concept to the Virgo kernel. Karaf has several functions that Virgo lacks, some of which are good candidates to add to Virgo. Apache Geronimo is based on Karaf.
GlassFish now has good support for OSGi. The EclipseCon tutorial started with us developing a basic client bundle calling a service published by a back-end bundle. We then replaced the client bundle with a WAB and the back-end bundle by a JPA persistence bundle which published a service in the form of an EJB. The WAB used custom annotations to inject the service into the WAB's servlet. The EJB was used to demarcate transactions and security. The M2Eclipse "core" and "extras" plugins provided a basic Eclipse development environment, although the bundles were deployed via the command line. Kudos to the GlassFish team, including Arun Gupta and Sanjeeb Sahoo who led the tutorial, for possibly the most polished hands-on tutorial I've experienced.
I was also very pleased to see the Eclipse Libra project making progress. The version destined for inclusion in this year's Eclipse release train can be used to develop WABs. Runtime launching support is in the pipeline. We also hope to migrate standards based features from the Virgo tooling into Libra.
