Creating an OSGi bundle

Newcomers to OSGi may like a simple guide to developing a bundle. Peter Kriens has provided an extensive tutorial (December 2008: currently offline pending an overhaul) which is a must for anyone serious about learning OSGi. However, it has a long introduction and assumes you are happy to run Eclipse. So I thought I would provide a trival example that people could get going using only a Java SDK and their favourite text editor.

Here are instructions to create and run a trivial bundle, hopefully in about 10 minutes.

1. Download an OSGi framework (I used Equinox v3.2.1).

2. Paste the following code into the file org/foo/example/Example.java:

package org.foo.example;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

public class Example implements BundleActivator {
public void start(BundleContext bc) {
System.out.println("Hello world");
}
public void stop(BundleContext bc) {
System.out.println("Goodbye world");  
}
}

3. Compile the code:

> javac -cp org.eclipse.osgi_3.2.1.R32x_v20060919.jar org/foo/example/Example.java

4. Paste the following bundle manifest into the file MANIFEST.MF:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-SymbolicName: org.foo.example.Example
Bundle-Version: 1
Bundle-Activator: org.foo.example.Example
Import-Package: org.osgi.framework;version="1.3.0"

Make sure you have a carriage return and/or newline character at the end of the last line as this is required (see manifest specification in the JAR specification).

5. Package the manifest and code into a bundle:

> jar cvfm example.jar MANIFEST.MF org

Note that the order of the flags is important - the f and m options need to appear in the same order as the jar file and manifest file parameters.

6. Run the resultant bundle example.jar interactively using the Equinox console, e.g.:

> java -jar org.eclipse.osgi_3.2.1.R32x_v20060919.jar -console

osgi> install file:///osgi/blog/example/example.jar
Bundle id is 6

osgi> start 6
Hello world

osgi> stop 6
Goodbye world

osgi> close

(close exits the framework).

That's it! Anyone care to comment how long it took them?