OSGi for mere mortals

This is the code of my "OSGi for mere mortals" presentation at ApacheCon NA 2011, EU 2012 and EU 2014.

It's a minimal standalone RESTful server built from scratch using OSGi Declarative Services, meant to demonstrate that OSGi is not only for superhuman guru programmers.

This example demonstrates the complete lifecycle of an OSGi application, from starting the framework and installing the required bundles to running the app itself.

It also demonstrates the svelteness of the OSGi framework and core services: the total size of the build-time dependencies (jar files) is around 3 megabytes and additional runtime baggage amounts to ten OSGi bundles (also jar files) representing about 2 megabytes more, including all runtime features like the OSGi web console, interactive OSGi shell, the OSGi configuration mechanism and front-end and the servlet engine. Startup time is around 300 msec on my laptop.

The Maven build is also a useful example of how to create OSGi bundles in a simple way.

The slides at http://www.slideshare.net/bdelacretaz/osgi-for-mere-mortals should help you walk through the code.

How to build and start

To build the runnable jar, run mvn clean install at the top of the source code tree (using Apache Maven 3.0.3 or later).

You can then start the server from the launcher subfolder by running

java -jar target/osgi-for-mere-mortals-launcher-0.0.1-SNAPSHOT.jar

(or whatever the name of that jar file is).

The OSGi console shown in the slides is at http://localhost:8080/system/console - use admin/admin to log in.

How to use the server

The server doesn't do much, that's not the point, the goal is just to demonstrate how it is assembled.

You can store data via HTTP POST requests:

$ date | curl -X POST -D - http://localhost:8080/store/testing
HTTP/1.1 201 Created
Location: /store/testing
Content-Type: text/plain; charset=utf-8
Content-Length: 149
Server: Jetty(6.1.x)

Stored at /store/testing
StoredBy:ch.x42.osgi.samples.osgi101.app.servlets.StorageServlet
StoredAt:Fri Nov 14 17:03:36 CET 2014

And retrieve it via HTTP GET:

curl http://localhost:8080/store/testing
StoredBy:ch.x42.osgi.samples.osgi101.app.servlets.StorageServlet
StoredAt:Fri Nov 14 17:03:36 CET 2014
Path:/store/testing