Appendix B. OSGi Best Practices

The following best practices are recommended for OSGi related tools and utilities:

Even for a moderately sized bundle project, it is usually impractical to create and maintain a bundle Manifest by hand. The Maven bundle plug-in is the most effective tool for automating the generation of bundle Manifests in a Maven project. See Section B.2, “Building OSGi Bundles”.

Avoid using the OSGi Java API directly. Prefer a higher level technology, for example: Blueprint (from the OSGi Compendium Specification), Spring-DM, Declarative Services (DS), iPojo, and so on.

The Blueprint container is now the preferred framework for instantiating, registering, and referencing OSGi services, because this container has now been adopted as an OSGi standard. This ensures greater portability for your OSGi service definitions in the future.

Spring Dynamic Modules (Spring-DM) provided much of the original impetus for the definition of the Blueprint standard, but should now be regarded as obsolescent. Using the Blueprint container does not prevent you from using the Spring framework: the latest version of Spring is compatible with Blueprint.

When an application is composed of a large number of bundles, it becomes essential to group bundles together in order to deploy them efficiently. Apache Karaf features is a mechanism that is designed just for this purpose. It is easy to use and supported by a variety of different tools. See Chapter 13, Deploying Features for details.

The OSGi Configuration Admin service is the preferred mechanism for providing configuration properties to your application. This configuration mechanism enjoys better tooling support than other approaches. For example, in Red Hat JBoss Fuse the OSGi Configuration Admin service is supported in the following ways:

In order for testing to be really effective, you should run at least some of your tests in an OSGi container. This requires you to start an OSGi container, configure its environment, install prerequisite bundles, and install the actual test. Performing these steps manually for every test would make testing prohibitively difficult and time-consuming. Pax-Exam solves this problem by providing a testing framework that is capable of automatically initializing an OSGi container before running tests in the container.

See Appendix C, Pax-Exam Testing Framework for more details.