OSGi Concepts

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The OSGi Alliance - Open Services Gateway initiative - is an open standards organization founded in March 1999 that originally specified and continues to maintain the OSGi standard. OSGi technology seems to be remarkably difficult to those unfamiliar with it.

Definitions:

1. The OSGi technology is a set of specifications that define a dynamic component system for Java.[1]

A software component is a unit of composition that can be developed independently with contractually specified interfaces and explicit context dependencies.[2]

OSGi enables the development of applications from components that could be:

• reusable
• dynamically composed
• hide their implementation
• communicate their dependencies and services

2. Bundle is the name for a component in the OSGi Architecture.

(generic bundle definition - a group of things fastened together for convenient handling[3] )

OSGi Framework The following list contains a short definition of the terms:

• Bundles - Bundles are the OSGi components made by the developers.
• Services - The services layer connects bundles in a dynamic way by offering a publish-find-bind model for plain old Java objects.
• Life-Cycle - The API to install, start, stop, update, and uninstall bundles.
• Modules - The layer that defines how a bundle can import and export code.
• Security - The layer that handles the security aspects.
• Execution Environments - Defines what methods and classes are available in a specific platform.

The core component of the OSGi Specifications is the OSGi Framework. The Framework provides a standardized environment to applications with the layers described above. The most used implementations of OSGi Specifications are Knopflerfish and equinox

Interactions between layers