How to Convert a jar File into an OSGi Bundle

Description

How do I convert an existing jar file into an OSGi bundle?

Resolution

Here’s a very simple way of turning an existing jar file in an OSGi bundle, while keeping control on exported packages.

The example creates an OSGi bundle from the attached junit-4.4.jar.

Note: The method below only works in a scenario where the jar file has no dependencies on other external jar files.

1. Start by creating a the jar’s manifest file:

   Manifest-Version: 1.0
   Created-By: myself
   Bundle-ManifestVersion: 2
   Bundle-Name: JUnit 4.4 bundle
   Bundle-Description: Package junit 4.4 in an OSGi bundle
   Bundle-Version: 4.4.0
   Bundle-ClassPath: .,junit-4.4.jar
   Bundle-SymbolicName: org.junit.framework
   Export-Package: junit.framework,junit.extensions,org.junit.runner,org.junit,junit.textui
   

   • Bundle-ClassPath header is set to allow embedding the original jar as is. Make sure its value matches the filename of the jar that you are going to embed in the bundle.
   • Export-Package is a list of packages contained in the jar that you would like to make available to other bundles running in the OSGi Container.

2. Get the jar file.

3. Create the bundle jar file by running the following command:

   jar cvfm junit-4.4-bundle.jar manifest.txt junit-4.4.jar
   

   Where manifest.txt is the name of the manifest file created above.

   That’s it - the resulting jar file is an OSGi bundle the exports the packages listed in Export-Package above, using the classes of the embedded junit-4.4.jar.

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