OSGI Components

13 12 2007

Perhapse this is premature, but a quick look around Apache Felix and Spring OSGI (Sorry I should say Spring Modules…. why the name change ?) gives the impression that its not going to be too hard to make most of Sakai OSGI.

So what is needed?

Well we would have to upgrade to Spring 2.5, we would have to write a service definition for each bundle and convert/move the components.xml file into the right places to make them load properly… and then we would have to deal with all the out of band things that go on in Sakai over the classloader boundaries.

IMHO, this would be a more productive long term aim that trying to write our own re-loadable component manager in competition with the component lifecycle that OSGi provides.

I also notice that there is goos support in eclipse for automating the creation of new bundles as eclipse plugins are just OSGi bundles, but for us the more important thig appears to be that Felix and Spring Modules will work with little or no effort inside Tomcat if we use the top level container concepts.

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3 responses

13 12 2007
Ray Davis

As you say, the fit is extraordinarily close. The only reasons I currently lean towards a Sakai-specific approach first are:

* Antranig’s and my branches have already worked out what most of the issues would be, whereas the OSGi issues are still an unknown to me.

* The configuration syntax needed to support the Sakai-specific approach almost exactly matches the Spring-OSGi configuration syntax (except for not making clients explicitly declare that they want out-of-scope services), and so it should be easy to investigate a central move to Spring-OSGi in parallel with decentralized moves of individual components to the Sakai-specific approach.

These aren’t terribly huge reasons, though, and just a little bit more research might knock them out.

13 12 2007
Ray Davis

By the way, the reason for the name change is that OSGi the organization didn’t want its name included as part of the name of another group. I smell lawyers. 🙂

15 12 2007
Jason Shao

While not as familiar with the details as you, Ray, or Antranig — anything that cuts down on either:

a) Classloader hell
b) Sakai-specific XXX

is good progress in my book.




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