OSGi - Architecture

Architecture

Any framework that implements the OSGi standard provides an environment for the modularization of applications into smaller bundles. Each bundle is a tightly coupled, dynamically loadable collection of classes, jars, and configuration files that explicitly declare their external dependencies (if any).

The framework is conceptually divided into the following areas:

Bundles
Bundles are normal jar components with extra manifest headers.
Services
The services layer connects bundles in a dynamic way by offering a publish-find-bind model for plain old Java Interfaces (POJI) or Plain Old Java Objects POJO.
Services Registry
The API for management services (ServiceRegistration, ServiceTracker and ServiceReference).
Life-Cycle
The API for life cycle management for (install, start, stop, update, and uninstall) bundles.
Modules
The layer that defines encapsulation and declaration of dependencies (how a bundle can import and export code).
Security
The layer that handles the security aspects by limiting bundle functionality to pre-defined capabilities.
Execution Environment
Defines what methods and classes are available in a specific platform. There is no fixed list of execution environments, since it is subject to change as the Java Community Process creates new versions and editions of Java. However, the following set is currently supported by most OSGi implementations:
  • CDC-1.0/Foundation-1.0
  • CDC-1.1/Foundation-1.1
  • OSGi/Minimum-1.0
  • OSGi/Minimum-1.1
  • JRE-1.1
  • From J2SE-1.2 up to J2SE-1.6

Read more about this topic:  OSGi

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