JSIG material on OSGi and JSR 291

The presentation and demo's from last week's excellent JSIG meeting on OSGi and JSR 291 are now available from EclipseZone.

Knopflerfish OSGi tutorial

Thanks to some Australian OSGi users for providing a nice link to a Knopflerfish OSGi tutorial.

My example of how to create an OSGi bundle in under 10 minutes still takes some beating for simplicity (or triviality, if you prefer), but I do believe in giving beginners a really easy way in. If they're smart, they'll soon catch on.

Creating an OSGi bundle

Newcomers to OSGi may like a simple guide to developing an bundle. Peter Kriens has provided an extensive tutorial 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?