New OSGi Work - Features

As recently the OSGi R7 Core, Enterprise and Compendium specs were completed, work has started on the next specifications for OSGi R8. Over the coming few months we'll focus on some of the new work that is underway at OSGi, here on this blog. In this post, we'll look at OSGi Features.

OSGi Frameworks are being used in many different scenarios, from embedded devices and set-top boxes to UI desktop applications and enterprise back-end server applications.  As your OSGi-based application grows, so does the number of bundles that define the application. In many cases, OSGi applications can grow to hundreds of bundles or even more. When an application reaches such a number of bundles, it can become hard to fully understand the role of each and every bundle in the application.

For this reason, many open-source communities and commercial products have started to develop solutions to group features together into more chunky, reusable components. The existing solutions generally combine both a design mechanism for these larger components plus an accompanying runtime. For example, there are Apache Karaf Features, Eclipse Features, Apache Sling Features, OSGi Subsystems, and others.

OSGi Features focus on architecting groups of bundles, configuration, and metadata, defining a mechanism to describe these groups. The Features can at runtime be mapped to existing implementations that support such functionality and in this way provide portability across these.

For example, you might create a Feature that defines a web service to record and provide gaming high scores. Your Feature might use other existing Features that provides HTTP, Jax-RS and database access. As Feature definitions can be published into a repository, such as a Maven Repository, you can use other Features simply by referring to them using repository coordinates. Once your Feature is ready to be used, you can publish yours in a repository, so that others can use it as well.

OSGi Features are extensible so that you can store your own metadata, along with the declaration of your binaries and configuration. This keeps things that belong together, defined together. For example, let's say your application needs a specific database schema to run. You can then declare this inside your Feature, rather than in a side file which might get out of sync.  And, Features are a neat way to scope your entire application: if you want to create a Docker image with a slimmed down version of the Java runtime, your Feature definition is a great way to know what you need from Modular Java and what parts you don't need, and could even be used to generate a minimal runtime image.  As OSGi Features are defined using JSON, so they can be handled by tools and other runtimes, which can be useful when validating them or for processing custom extensions.

To summarize, OSGi Features are aimed at architecting reusable components for OSGi that are larger than bundles. OSGi Features are a design artifact, they don't mandate a specific runtime for it. Therefore OSGi Features can be mapped to existing technologies that already exist in this space, or be used as-is by tools and runtimes that natively handle them.

To learn more about OSGi Features. they are being discussed in RFP 188 and RFC RFC 241. Both can be found at the OSGi design github repo: https://github.com/osgi/design

OSGi Community Event 2019 Early Bird Pick & Registration Now Open

Congratulations to Raymond Augé from Liferay, Inc. for being selected as the Early Bird pick!  The title of his talk submission is OSGi CDI Integration Specification.

Abstract
The OSGi Alliance has developed a specification describing integration between OSGi and CDI. The combination of these two powerful development technologies opens the door to new possibilities. This talk will walk through the most essential features of the specification and show some code and running examples

About Raymond Augé 
Raymond Augé is a Sr. Software Architect at Liferay, Inc. As an Apache Software Foundation member and PMC of Apache Aries; Apache Felix and Apache Geronimo projects; committer on the Bndtools.org project; lead of the Eclipse Project for Common Annotations specification; committer and company representative at the Eclipse Foundation and OSGi Alliance Board of Directors and Enterprise Expert Group co-chair; Raymond demonstrates a vigorous passion for open source and open standards.

Event Registration
If you are already planning on joining us you will be pleased to know that Registration for the event is now open and you can secure the best prices by booking early.