How to include a dependency to a jar file from an eclipse/osgi application?

Question

I created an Eclipse 4 application and I needed a jar offering a functionality as part of my application (this could be anything e.g. log4j to make

Answer 1

Extactaly same problem we faced in our project. we have some legacy jar which are not OSGi compatible, we create lib folder parallel to BundleContent and added it into the classpath section of manifest.

Bundle-ClassPath: .,

 /lib/<legacy jar>.jar

There is no need to exporting and importing of packages unnecessarily if only one bundle is going to consume it,

Answer 2

For the runtime it is always the Manifest and the headers there that control what is in your bundle classpath. There are three ways to get access to a jar:

1. Import-Package header. This is the recommended way. You define one import per package you need. You jar you want to access has to be deployed in the runtime as a bundle. It also needs to export all needed packages.

2. Require-Bundle . This is another way to access bundles. You define the id of the bundle you need and see all packages it exports. As Require-Bundle binds you more closely to the other bundle the Import-Package way should be preferred.

3. Bundle-Classpath . This allows to add jars to your classpath that you embed into your own bundle. This should only be a last resort when the other way do not work. You can have nasty classloading issues when mixing this with the other methods.

You can find many pre built bundles in maven central. Many jars today already contain an OSGi manifest. For the cases where this is not true many jars are repackaged as bundles by servicemix. See groupId: org.apache.servicemix.bundles. There is also the spring bundle repository where you find some more.

Below I listed some resources you might want to read:

http://www.aqute.biz/Blog/2007-02-19

http://wiki.osgi.org/wiki/Import-Package

http://wiki.osgi.org/wiki/Require-Bundle

http://www.vogella.com/blog/2009/03/27/required-bundle-import-package/

Answer 3

The examples you have mentioned are available as OSGi bundles, so you don't need to make them bundles yourself. You don't typically use direct jar dependencies in OSGi, you typically use package or bundle dependencies. In the log4j example you are referring to, you should use import package as there can be multiple bundle providers (newer log4j jar, springsource bundled version of older log4j, slf4j implementation...). This will disconnect your code dependencies from the actual provider.

These dependencies are maintained via you manifest, not your project classpath. In an eclipse plugin project, the projects build classpath is derived from the entries in the manifest.

Even though you are not using services, all code dependencies are still maintained via the manifest.