What's the best way to get started with OSGI? [closed]

Answer 1

When learning a new technology rich tooling gets you into things without big headaches. At this point the community at ops4j.org provides a rich toolset called "PAX" which includes:

• Pax Runner: Run and switch between Felix, Equinox, Knopflerfish and Concierge easily
• Pax Construct: Construct, Organize & Build OSGi projects with maven easily
• Pax Drone: Test your OSGi bundles with Junit while being framework independent (uses PaxRunner)

Then there are many implementations of OSGi compendium services:

• Pax Logging (logging),
• Pax Web (http service),
• Pax Web Extender (war support),
• Pax Coin (configuration),
• Pax Shell (shell implementation, part of the next osgi release)
• and much more.

.. and there is a helpful, framework independend community, - but thats now advertisement ;-)

Answer 2

Is your existing application monolithic or tiered in seperate processes/layers?

If tiered, you can convert the middle/app-tier to run in an OSGi container.

In my team's experience, we've found trying to do web-stuff in OSGi painful. Other pain points are Hibernate and Jakarta Commons Logging.

I find the OSGi specs pretty readable and I recommend you print out the flowchart that shows the algorithm for class loading. I'll guarantee you'll have moments of, "why am I getting a NoClassDefFoundError?": the flowchart will tell you why.

Answer 3

Try http://njbartlett.name/files/osgibook_preview_20091217.pdf

OR

http://www.manning.com/hall/

The second is not a book i have read myself but I have heard good things about it.

The first was very useful for me. He takes you through the architecture initially and then it's hands on OSGi.

Answer 4

There are a couple of thinks to keep in mind if you are starting with OSGi.

As mentioned elsewhere in this thread, knowing about classloading is really important. In my experience everybody sooner or later runs into problems with it.

Another important thing to remember is: never hold references! Have a look at the whiteboard pattern on which the services concept of OSGi is build (see the link in one of the other answers).

In my experience you should not try to convert a monolitic application into an OSGi-based one. This usually leads to a badly and unmanageable mess. Start anew.

Download one of the freely available stand-alone OSGi implementations. I found Knopflerfish rather good and stable (I use it in many projects). It also comes with lots of source code. You can find it here: http://www.knopflerfish.org

Another good tutorial can be found here. https://pro40.abac.com/deanhiller/cgi-bin/moin.cgi/OsgiTutorial

Peter Kriens of the OSGi Alliance gave a nice interview: http://www.infoq.com/interviews/osgi-peter-kriens. His homepage and blog (which is always a good read can be found here: http://www.aqute.biz

Answer 5

Try http://neilbartlett.name/blog/osgibook/. The book has hands on examples with OSGi best practices.

Answer 6

I really like the Apache Felix tutorials. However, I think in general leveraging OSGi in your application isn't one of those "let's use this framework, because it's hype" decision. It's more of a design question, but then everything that OSGi gives you in terms of design, you can have with vanilla Java as well.

As for the runtime, you cannot just add an existing application and make it OSGi enabled. It needs to be design to be dynamic. Spring DM makes it easy to hide that from you, but it's still there and you need to be aware of it.