The OSGi Alliance, formerly known as the Open Services Gateway initiative, is an open standards organization founded in March 1999 that originally specified and continues to maintain the OSGi standard.
The OSGi specification describes a modular system and a service platform for the Java programming language that implements a complete and dynamic component model, something that does not exist in standalone Java/VM environments. Applications or components, coming in the form of bundles for deployment, can be remotely installed, started, stopped, updated, and uninstalled without requiring a reboot; management of Java packages/classes is specified in great detail. Application life cycle management is implemented via APIs that allow for remote downloading of management policies. The service registry allows bundles to detect the addition of new services, or the removal of services, and adapt accordingly.
The OSGi specifications have evolved beyond the original focus of service gateways, and are now used in applications ranging from mobile phones to the open-source Eclipse IDE. Other application areas include automobiles, industrial automation, building automation, PDAs, grid computing, entertainment, fleet management and application servers.
The OSGi specification is developed by the members in an open process and made available to the public free of charge under the OSGi Specification License. The OSGi Alliance has a compliance program that is open to members only. As of November 2010, there are seven certified OSGi framework implementations. A separate page lists both certified and non-certified OSGi Specification Implementations, which include OSGi frameworks and other OSGi specifications.
OSGi (Open Service Gateway Initiative) is a Java framework for developing and deploying modular software programs and libraries. 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:
BundlesBundles are normal jar components with extra manifest headers.
ServicesThe 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 RegistryThe application programming interface for management services (ServiceRegistration, ServiceTracker and ServiceReference).
Life-CycleThe application programming interface for life cycle management (install, start, stop, update, and uninstall) for bundles.
ModulesThe layer that defines encapsulation and declaration of dependencies (how a bundle can import and export code).
SecurityThe layer that handles the security aspects by limiting bundle functionality to pre-defined capabilities.
Execution EnvironmentDefines 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-1.0CDC-1.1/Foundation-1.1OSGi/Minimum-1.0OSGi/Minimum-1.1JRE-1.1From J2SE-1.2 up to J2SE-1.6A bundle is a group of Java classes and additional resources equipped with a detailed manifest MANIFEST.MF file on all its contents, as well as additional services needed to give the included group of Java classes more sophisticated behaviors, to the extent of deeming the entire aggregate a component.
Below is an example of a typical MANIFEST.MF file with OSGi Headers:
Bundle-Name: Hello WorldBundle-SymbolicName: org.wikipedia.helloworldBundle-Description: A Hello World bundleBundle-ManifestVersion: 2Bundle-Version: 1.0.0Bundle-Activator: org.wikipedia.ActivatorExport-Package: org.wikipedia.helloworld;version="1.0.0"Import-Package: org.osgi.framework;version="1.3.0"
The meaning of the contents in the example is as follows:
Bundle-Name: Defines a human-readable name for this bundle, Simply assigns a short name to the bundle.Bundle-SymbolicName: The only required header, this entry specifies a unique identifier for a bundle, based on the reverse domain name convention (used also by the java packages).Bundle-Description: A description of the bundle's functionality.Bundle-ManifestVersion: Indicates the OSGi specification to use for reading this bundle.Bundle-Version: Designates a version number to the bundle.Bundle-Activator: Indicates the class name to be invoked once a bundle is activated.Export-Package: Expresses which Java packages contained in a bundle will be made available to the outside world.Import-Package: Indicates which Java packages will be required from the outside world to fulfill the dependencies needed in a bundle.A Life Cycle layer adds bundles that can be dynamically installed, started, stopped, updated and uninstalled. Bundles rely on the module layer for class loading but add an API to manage the modules in run time. The life cycle layer introduces dynamics that are normally not part of an application. Extensive dependency mechanisms are used to assure the correct operation of the environment. Life cycle operations are fully protected with the security architecture.
Below is an example of a typical Java class implementing the BundleActivator interface:
Standard services
The OSGi Alliance has specified many services. Services are specified by a Java interface. Bundles can implement this interface and register the service with the Service Registry. Clients of the service can find it in the registry, or react to it when it appears or disappears.
The table below shows a description of OSGi System Services:
The table below shows a description of OSGi Protocol Services:
The table below shows a description of OSGi Miscellaneous Services:
The OSGi Alliance was founded by Ericsson, IBM, Motorola, Sun Microsystems and others in March 1999. Before incorporating as a nonprofit corporation it was called the Connected Alliance.
Among its members are (as of February 2015) more than 35 companies from quite different business areas, for example Adobe Systems, Deutsche Telekom, Hitachi, IBM, Liferay, Makewave (formerly Gatespace Telematics), NEC, NTT, Oracle, Orange S.A., ProSyst, Salesforce.com, Siemens, Software AG and TIBCO Software.
The Alliance has a board of directors that provides the organization's overall governance. OSGi officers have various roles and responsibilities in supporting the alliance. Technical work is conducted within Expert Groups (EGs) chartered by the board of directors, and non-technical work is conducted in various working groups and committees. The technical work conducted within Expert Groups include developing specifications, reference implementations, and compliance tests. These Expert Groups have produced five major releases of the OSGi specifications (As of 2012).
Dedicated Expert Groups exist for the enterprise, mobile, vehicle and the core platform areas.
The Enterprise Expert Group (EEG) is the newest EG and is addressing Enterprise / Server-side applications. In November 2007 the Residential Expert Group (REG) started to work on specifications to remotely manage residential/home-gateways. In October 2003, Nokia, Motorola, IBM, ProSyst and other OSGi members formed a Mobile Expert Group (MEG) that will specify a MIDP-based service platform for the next generation of smart mobile phones, addressing some of the needs that CLDC cannot manage - other than CDC. MEG became part of OSGi as with R4.
OSGi Release 1 (R1): May 2000OSGi Release 2 (R2): October 2001OSGi Release 3 (R3): March 2003OSGi Release 4 (R4): October 2005 / September 2006Core Specification (R4 Core): October 2005Mobile Specification (R4 Mobile / JSR-232): September 2006OSGi Release 4.1 (R4.1): May 2007 (AKA JSR-291)OSGi Release 4.2 (R4.2): September 2009Enterprise Specification (R4.2): March 2010OSGi Release 4.3 (R4.3): April 2011Core: April 2011Compendium and Residential: May 2012OSGi Release 5 (R5): June 2012Core and Enterprise: June 2012OSGi Release 6 (R6): June 2015Core: June 2015RFC 2608 (Service Location Protocol)Sun JiniSun JCP JSR-8 (Open Services Gateway Specification)Sun JCP JSR-232 (Mobile Operational Management)Sun JCP JSR-246 (Device Management API)Sun JCP JSR-249 (Mobile Service Architecture for CDC)Sun JCP JSR-277 (Java Module System)Sun JCP JSR-291 (Dynamic Component Support for Java SE - AKA OSGi 4.1)Sun JCP JSR-294 (Improved Modularity Support in the Java Programming Language)MHP / OCAPUniversal Plug and Play (UPnP)DPWSITU-T G.hnLonWorksCORBACEBusEHS (KNX) / CECED CHAINJava Management ExtensionsApache Aries - Blueprint Container implementations and extensions of application-focused specifications defined by OSGi Enterprise Expert Group.Apache Sling - OSGi-based applications layer for JCR content repositoriesAtlassian Confluence and JIRA - the plug-in architecture for this enterprise wiki and issue tracker uses OSGiBusiness Intelligence and Reporting Tools (BIRT) Project - Open source reporting engineCytoscape - an open source bioinformatics software platform (as of version 3.0)DataNucleus - open source data services and persistence platform in service-oriented architecturesDotcms - open source Web Content ManagementEasyBeans - open source EJB 3 containerEclipse - open source IDE and rich client platformEnprovia - mobile integration middleware, commercial OSGi implementationiDempiere - is an OSGi implementation of the open source ERP Branch GlobalQSS Adempiere361 originally started by Low Heng Sin.Eclipse Virgo - open source microkernel-based server constructed of OSGi bundles and supporting OSGi applicationsGlassFish (v3) - application server for Java EEFuse ESB - a productized and supported release of ServiceMix 4.ServiceMix - Apache ServiceMix is a flexible, open-source integration container that unifies the features and functionality of following components: Apache ActiveMQ, Apache Camel, CXF, and Apache Karaf into a powerful runtime platform. The components are always really outdated. You can use servicemix to build your own integrations solutions and it provides a complete, enterprise ready ESB exclusively powered by OSGi.GX WebManager Community Edition - An Enterprise Web Content Management System based on OSGi, spring and JCRKura - Eclipse IOT open source project for M2M applications [1]IntelliJ - Java IDE and rich client platform with free community editionJBoss - Red Hat's JBoss Application ServerJOnAS 5 - open source Java EE 5 application serverJOSSO 2 - Atricore's open source standards-based Identity and Access Management PlatformLiferay - a free and open source enterprise portal platformLucee 5 - open source CFML Web Application ServerNetbeans - open source IDE and rich client platformNuxeo - open source ECM Service PlatformOpen Daylight Project - Project with the goal of accelerating the adoption of software-defined networkingOpenEJB - open source OSGi-enabled EJB 3.0 container that can be run both in standalone or embedded modeOpenWorm - open source software simulation of C. Elegans, via the dedicated Geppetto modular platformopenHAB - open source software for integrating different home automation systems [2]Paremus Service Fabric - distributed OSGi platform supporting OSGi, Java and non-Java artifacts for IoT Edge Computing, Cloud and EnterpriseAkana - API Gateway, Portal and Analytics server from Akana (formerly SOA Software)SpringSource dm Server - open source microkernel-based server constructed of OSGi bundles and supporting OSGi applicationsWeblogic - Oracle Weblogic Application ServerWebSphere - IBM Websphere JEE Application ServerWebMethods - SoftwareAG WebMethodsWSO2 Carbon - Base platform for WSO2’s enterprise-grade Open source middleware stack.
