Skip to main content

(NOT) yet Another Getting Started with OSGi

Last week I have been learning OSGi.

I got my first application running in OSGi. I am not going to write another getting started post with code that will show a hello world. But rather give you an idea how to start getting in the mud. And then may be show you more than a direction :)

I used Equinox 3.4 (OSGi R4) implementation. I prefered it over Felix. Why - Eqinox is simple, and a single jar download. But I guess that aint a thing to notice. You can get Equinox jar from here. If the link is broken, go here, download the equinox framework, it should be ~0.95MB.

Start equinox framework as
java -jar equinox.jar -console
You would have seen this on a lot of sites. but I did fall on two things flat on my face; missing -console and doing it wrong --console :P

As per the spec, (and by now, you know) a bundle is a jar with some special informtion in MANIFIEST.MF. A Bundle jar need not DO anything. It could just sit installed or be active (by exporting packages and services). So if you have a jar with just one interface that defines a static final variable: It can be jar-ed to a bundle too. It may not do much (other than exposing the constant). but it is a Bundle.

And then, There is a starter interface is BundleActivator. No I am not writing Hello World program. This interface can be used by adding
Import-Package: org.osgi.framework
manifest header(mind the space after the colon). Along with that, You need to point (only one) a class that implements this interface (start() and stop()) to handle the call backs by adding
That gives you enormous power to do a loooot of things in OSGi. You are now literally the master of the universe (or atleast of the framework instance :P). Because with these two hooks (callback methods) you can traverse through the BundleContext. The BundleContext(, like ServletContext) exposes you to a lot of things around you. The framwork, The bundles living with you, Thier metadata, Their statuses, mechanism to programatically do stuff..

errr.. its 22:10, I gotta go to bed now.. If you want to learn more, Dont download a book. Start with the code. You can figure? Start with this one. I will see you in the next post..

Popular posts from this blog

Javascript: Convert Strings to Binary (and representing in a nerdy way!)

I follow those GoogleDevelopers Videos. Sometime back, in one of the presentations on GoogleIO, there was this interesting string of dots at the bottom of each page of the presentation. They looked like random big and small dots. A similar bunch of dots were also on the T-shirt of a presenter was wearing in another presentation. While it seemed something in the pattern, I could not find what it was. Finally, another presenter cleared the matter that those dots are just binary representation of "GOOGLEIO" (So much for advertizing Google IO, Impressive!).

So I wanna do it. Takes me back to days of those DSP classes at school. Nerdy me had to churn some old brain cells. I remember those first programming language classes in Pascal and C when you were asked to do fibonacci series and converting a binary string to ascii codes. That *experience* came handy here: Check it out!

Text to Binarize:
For those who came to copy the javascript code to convert string to binary, Here it is…

Add jquery in Chrome console

Many a time, a page you are debugging doesnot have jquery. This simple js will add(or prompt you to overwrite) jquery to any page from chrome console.


The easiest way to install docker on Ubuntu

Docker releases come out faster than ubuntu updating thier repositories. Docker mainitains a ppa. One can add the ppa key, and then add to sources.list.d and then update sources and then install lxc-docker. OR..
curl -sSL | sudo sh