OSGi
From Wikipedia, the free encyclopedia
| OSGi Service Platform | |
|---|---|
 |
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| Developed by | OSGi Alliance |
| Latest release | 4.1 / May 2007 |
| OS | Java |
| Genre | standards organization |
| License | OSGi Specification License |
| Website | http://www.osgi.org |
The OSGi Alliance (formerly known as the Open Services Gateway initiative - now an obsolete name) is an open standards organization founded in March 1999. The Alliance and its members have specified a Java-based service platform that can be remotely managed. The core part of the specifications is a framework that defines an application life cycle management model, a service registry, an Execution environment and Modules. Based on this framework, a large number of OSGi Layers, APIs, and Services have been defined.
[edit] OSGi Framework Scope
The Framework implements a complete and dynamic component model, something that is missing 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. Life cycle management is done via APIs which 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 original focus was on service gateways but the applicability turned out to be much wider. The OSGi specifications are now used in applications ranging from mobile phones to the open source Eclipse IDE. Other application areas include cars, industrial automation, building automation, PDAs, grid computing, entertainment (e.g. iPronto), fleet management and application servers.
[edit] Specification Process
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 [1]. The OSGi Alliance has a compliance program that is open to members only. As of October 2007, the list of certified OSGi implementations contains six entries.
[edit] Architecture
Frameworks that implement the OSGi standard provide 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:
- Module – encapsulation and declaration of dependencies
- Life Cycle – API for life cycle management
- Service Registry – providing functionality to other bundles
- Security layer - limit bundle functionality to pre-defined capabilities
[edit] Organization
The OSGi Alliance was founded by Ericsson, IBM, Oracle, 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 May 2007) more than 35 companies from quite different business areas, for example IONA Technologies, Ericsson, Deutsche Telekom, IBM, Makewave (formerly Gatespace Telematics), Motorola, Nokia, NTT, Oracle, ProSyst, Red Hat, Samsung Electronics, Siemens, and Telefonica.
The Alliance has a Board of Directors which 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, working together, have produced four major releases of the OSGi specifications (as of 2007).
There are dedicated Expert Groups 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.
[edit] Community
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.
Also in 2003 Eclipse selected OSGi as the underlying runtime for the plug-in architecture used for the Eclipse Rich Client Platform and the IDE platform. Eclipse itself includes sophisticated tooling for developing OSGi bundles and there are a number of other Eclipse plug-ins aimed at supporting OSGi behaviour (e.g. both ProSyst and Knopflerfish have Eclipse plug-ins available specifically for OSGi developers).
There is a vibrant free software community revolving around the OSGi. Some widely-used open source implementations are Equinox OSGi, Apache Felix [1], Knopflerfish OSGi project as well as the mBedded Server Equinox Edition.
[edit] Specification Versions
- OSGi Release 1 (R1): May 2000
- OSGi Release 2 (R2): October 2001
- OSGi Release 3 (R3): March 2003
- OSGi Release 4 (R4): October 2005 / September 2006
- Core Specification (R4 Core): October 2005
- Mobile Specification (R4 Mobile / JSR-232): September 2006
- OSGi Release 4.1 (R4.1): May 2007 (AKA JSR-291)
[edit] New in OSGi Release 4
The new features of OSGi R4 in brief are as follows :
- Powerful new modularization capabilities providing enhanced encapsulation of networked services that can share a single VM.
- Modularized class sharing and hiding of implementation details.
- Advanced handling of multiple versions of the same classes so old and new applications can execute within the same VM.
- Localization of OSGi bundle manifests enabling service deployment anywhere.
- Enhancements in security and policies: The new Conditional Permission Admin service provides an elegant and simple way to manage networked services securely. It also supports dynamic policies that can depend on external (custom) conditions. Combined with R4 support for digital signatures, this provides a central security solution to large deployments of products using the OSGi Service Platform.
- A Declarative Services specification that addresses memory footprint issues that can prevent small embedded devices from using a service oriented architecture to support multiple applications. Additionally, it significantly simplifies the service-oriented programming model by declaratively handling the dynamics of services.
- Compatibility with Release 3, requiring no changes for existing OSGi bundles, applications, or services.
[edit] Guidance and Information Exchange
- Frequently Asked Questions
- OSGi Developer Mail List
- Eclipse Equinox Article Index - Articles on an open source OSGi implementation
- ProSyst - Access to supported Open Source and Commercial OSGi implementations as well as to 100+ inhouse OSGi developers, seminars, trainings, consulting and custom development services
- aQute: OSGi Info - Information about OSGi and access to seminars
- OSGi Users' Forums - Japan, Korea, France, Spain, Sweden, and soon : Italy, Germany
[edit] Related RFCs and Java Specifications
- RFC-2608 (Service Location Protocol)
- Sun JINI (Java Intelligent Network Infrastructure)
- Sun 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)
[edit] Related Technology Standards
- MHP / OCAP
- Universal Plug and Play (UPnP)
- Universal Powerline Association
- HomePlug
- LonWorks
- CORBA
- CEBus
- EHS (KNX) / CECED CHAIN
- X10
- Java Management Extensions
[edit] Examples of Projects Using OSGi
- Datanucleus - open source data services and persistence platform in service oriented architectures
- EasyBeans - open source EJB 3 container
- Eclipse - open source IDE and rich client platform
- Nuxeo - open source ECM Service Platform
- JOnAS 5 - open source Java EE 5 application server
- JPOX - open source object-relational mapper
- Newton - open source distributed OSGi/SCA runtime
- Business Intelligence and Reporting Tools (BIRT) Project - Open source reporting engine
- Apache Sling - OSGi-based applications layer for JCR content repositories.
- GlassFish (v3) - application server for J2EE
- Project Fuji in Open ESB v3 - Light weight and modular ESB core runtime.
- SIP Communicator - open source Java VoIP and multi-protocol instant messenger
- Spring Source Application Platform - A module-based Java application server built on Spring, Tomcat and OSGi-based technologies.
[edit] References
[edit] Books
- OSGi Service Platform, Release 3, IOS Press, ISBN 1-58603-311-5
- Programming Open Service Gateways with Java Embedded Server(TM) Technology, ISBN 0-20171-102-8
[edit] Webinar
- Part 1 of a webinar series on OSGi – Running OSGi
- Part 2 of a webinar series on OSGi - Installing some bundles
- Part 3 of a webinar series on OSGi – Running some games
- Part 4 of a webinar series on OSGi – Installing a php wiki on top of OSGi
- OSGi Best Practices by OSGi Fellows Hargrave and Kriens at JavaOne 2007
- OSGi, the good the bad the ugly
[edit] See also
[edit] External links
- OSGi Technology
- OSGi web site
- OSGi Alliance Developer Site
- The Eclipse 3.0 platform: Adopting OSGi technology
- ApacheCon EU 2006 presentation about OSGi best practices by Marcel Offermans.
- Nuxeo Runtime Documentation -- Nuxeo, open source Enterprise Content Management (ECM) solution built on OSGi technology
- Interview with Kriens and Hargrave (Podcast)
- An Introduction to OSGi on the Server Side by Daniel Rubio
- SOA World Article:What's happening with OSGi and why you should care by David Chappell and Khanderao Kand
