Enterprise OSGi and Apache Aries in London
I dont too often manage to get along to LJC events, but I really enjoyed last night's talks by Neil Bartlett (on Enterprise OSGi) and Zoe Slattery (on Apache Aries).
OSGi seems to have been on a slow but steady ascendency curve for a really long time, but there does now seem to be quite a few more areas of growth beyond the usual eclipse project and set top box builders. With most of the app server vendors and middleware players investing in some substantive way into modularisation via OSGi, the technology is encroaching much further now into the traditional enterprise java space.
Neil firstly ran through the basics of what OSGi is all about, before unpacking what the recently released OSGi 4.2 Blueprint is all about. Many of the traditional areas of the enterprise java stack (JDBC, JTA, Web containers) are addressed in some way by this recent release, but there are still a number of key areas (such as JMS and JCA) which have not made it in, this time round.
Most of the OSGi fundamentals werent new to me, but one thing I did take away from Neil's explaination was the notion of component adaptability. When considering Component Oriented Programming, Neil likened a component to a biological unit and its relationship with its environment. A bio unit can be placed (read reused) into different environments. In an ideal environment it will thrive. In a suboptimal one, it will try to adapt. The key here being that adaptability promotes reusability, particularly when considering environments that change dynamically at runtime.
Zoe Slattery, who works for IBM, and contributes to the Apache Aries project spoke about the short history of Aries and gave a quick demonstration of one of the simpler sample projects that she looks after as part of her Apache project role. It was good to see this practical demonstration to back up Neil's more theoretical talk. Interestingly, Zoe mentioned how the recent inception of the Eclipse Gemini project had come as quite an unexpected suprise to many in the Apache/Geronimo space from which Aries has emerged.
I havent played with Aries yet, but the talk was enough to convince me to give it a go sometime soon (watch this space). Its still really early days for Aries (its in the Apache Incubator), but it will be interesting to see how it grows, and particularly areas that compliment or cross over with Eclipse Geronimo.
For me, I think the 4.2 spec looks like a great step forward, making available in the OSGi space many technologies that one really cannot work without in the enterprise. But the ommissions (notably JMS and JCA) also seem pretty big, and with the tectonic slowness that these specifications have moved, it will likely be sometime before these gaps are filled.
“The maven, osgi, & spring combo, is about to happen”
.... taking a quick quote from Jilles Van Gurp, that I couldnt help but agree with.
The combination of dependency injection (Spring), runtime modularisation (OSGi) and compile/package time modularisation (Maven2) seems powerful, interrelated, and somewhat inevitable. The degree of crossover between these tools however suggests that some of the architectural design flaws in Java itself with respect to packaging and reuse are now bubbling to the surface in several places at once.
With the lack of language support for modularisation, it will be interesting to see which (if any) of these three technologies becomes the central tool in a developers toolkit. Considering the degree to which the Spring guys have embraced OSGi, my money would be on Spring.