Incremental OSGi with Virgo, Gemini, and Libra

As I anticipate the start of EclipseCon 2011 later today, I'm reflecting on the current state of the Eclipse Virgo, Gemini, and Libra projects.

As I'll be discussing on Tuesday, Virgo evolved out of a relatively mature project whose aim was to make it easy for enterprise applications and enterprise application developers to adopt OSGi. The goal was to make the transition to OSGi incremental. Essentially you can start with a standard WAR file and deploy it to Virgo as-is. Then you can incrementally refactor the WAR file into an application comprising multiple OSGi bundles while continuing to use familiar technologies such as Spring, Hibernate, JPA, etc. We based Virgo on Tomcat suitably embedded into OSGi, again to provide familiarity for enterprise developers as well as systems administrators.

In parallel with the evolution of Virgo, the OSGi Alliance Enterprise Expert Group, being discussed on Tuesday, produced a series of enterprise specifications again with the goal of enabling enterprise applications to be migrate straightforwardly to OSGi. The reference implementations of these specifications became today's Eclipse Gemini project:

• Gemini Blueprint - an OSGi standard dependency injection container which also supports the popular Spring and Spring DM namespaces
• Gemini Web - support for servlets in the form of OSGi standard Web Application Bundles (WABs) or standard WAR files
• Gemini JPA - support for JPA persistence in OSGi
• Gemini DBAccess - modularised JDBC drivers for use in OSGi
• Gemini Management - JMX management for OSGi
• Gemini Naming - support for JNDI naming in OSGi

Until recently, integrating the Gemini projects into Virgo has been a fairly specialised skill. As we'll see in a workshop on Thursday, things are now really starting to come together and Gemini Blueprint, Gemini Web, and various other Gemini components can now be deployed and used in Virgo. We'll also be touching on how to manage and configure WABs in Virgo as part of a workshop later this morning.

So much for the past. What about the future? The primary goal of Virgo 3.0 is better integration with other EclipseRT technologies such as Equinox, Jetty, and p2. This will provide richer function and greater choice for enterprise applications as they migrate to OSGi. We'll be hearing about how Virgo and EclipseRT technologies work together on Wednesday. The recently released third milestone of this release shows the progress towards the goal of better integration with EclipseRT:

• Virgo now uses Equinox Configuration Admin and Event Admin services instead of their Apache equivalents.
• Virgo has moved to the new framework hooks model for isolation in Equinox which is part of the OSGi 4.3 standard soon to be issued for public review.
• Virgo now provides two web servers: Virgo Tomcat Server, which continues to be based on Gemini Web, and Virgo Jetty Server. Some exciting technology for modularising the view portion of web applications is also emerging into the Virgo mainstream as we'll hear on Wednesday.
• p2 support in Virgo is also making good progress although this is currently in prototype form.

Development tooling is also entering an exciting new phase which will greatly help applications migrate to enterprise OSGi:

• The Libra project, which will be presented on Wednesday, is providing development tooling for building WABs and will ship in the Eclipse Indigo release train later this year.
• The Virgo development tooling has entered the Eclipse IP process and will soon emerge in the Virgo project. Over time, the standards-based features of the Virgo tooling will be factored out and migrated into Libra.
• OSGi runtime launchers are also being contributed to Libra. I would hope to see a Virgo launcher for Libra emerge so that Libra can start to take over from the Virgo tooling for many aspects of enterprise OSGi application development.

If you're attending EclipesCon, come and hear the talks, join in the workshops and BoFs and help to shape incremental OSGi in the Virgo, Gemini, and Libra projects.