OSGi

Now take all of that and wrap it up into a controlled runtime where plug-ins can come and go dynamically, and you get OSGi (basically).

Our OSGi container is now ready to rock and roll for some distributed service deployments.

ML: OSGi has been around for quite a while, but it's only recently that it seems to have received a lot of attention.

Although it's outside of the scope of this article, it's possible to have multiple versions of a bundle in an OSGi system at once.

He said that OSGi has been a part of IBM's strategy but it has been used mainly for the internal projects (like WebSphere and Eclipse).

The application manifest shown in Listing 10 needs to indicate that this service should be visible outside the OSGi application.

This enables OSGi based systems to be brought up in an orderless fashion, and for bundles to be run independently of one another.

As you have seen already, the place (in an OSGi environment) to exchange services is the OSGi service registry.

Fortunately, OSGi manages such transitive dependencies for you, and ensures that you never have problems due to incompatible classes.

The OSGI-INF directory (along with XML files) needs to be included in the bundle, as otherwise DS won't be able to see it.

RAP is a AJAX framework with a server-side focus and a strong tie into OSGi, Equinox and the Eclipse Platform.

The Hamlet bundle shows up in the bundle view when you load it from the Knopflerfish OSGi desktop, as you can see in Figure 6.

These methods allows you to hook into the lifecycle of the add-on, which is managed by the underlying Roo OSGi container.

Version Tracking - OSGi provides versioning support to address the question of Can I integrate with this library?

As an OSGi solution, Nuxeo components can be contributed through the addition of OSGi bundles with a Nuxeo-Component header.

InfoQ: Speaking of new technologies, OSGi seem to be emerging as well as an important technology, how do you position SCA and OSGi?

It is possible to convert the Web module in the EAR into an OSGi bundle using changes similar to those you made to the persistence module.

makes it easy to build Spring applications that run in an OSGi framework.

The specification consists of two parts: the OSGi framework and a set of standard service definitions.

Equinox serves as the reference implementation for OSGi, which can be considered as forming the building blocks of Eclipse.

It is designed to deal with the dynamic nature of OSGi, where services can become available and unavailable at any time.

Not surprisingly, as the persistence unit is no longer defined by Java EE, no such name will be populated by the OSGi JPA runtime.

The latter will allow for a standard shell to control any OSGi engine, rather than the per-system shells at the moment.

He started off the presentation with an overview of OSGi Architecture and its Framework Layering.

The OSGi is a specification that defines and communicates the modularity of a Java application in a more dynamic way.

Eclipse comes with a useful OSGi console that allows you to test OSGi modules by installing and running them.

OSGi is not at all integrated with the Java language, however, having been built atop the Java SE Platform rather than from within it.

"I think OSGi is a great technology but I don't think it's the one and only possible answer either, " he said.

As you may know, Equinox, the OSGi implementation that underpins Eclipse, is being used quite extensively on servers these days.

As such, from an architectural perspective, OSGi is just a specific packaging technology.

We thought about the option of using OSGi bundles, but we were not able to do that: OSGi is really about a single process, a single JVM.

One solution to this problem is OSGi's declarative services, hereafter referred to as DS.

The software can be distributed to devices either as a software package or as an OSGi bundle, depending on the device class.

Transactions are provided as part of a JTA binding, which allows transactions to be acquired from an OSGi service.

In Eclipse, we are used to the word plug-in and in the OSGi community they are used to the word bundle.

When a dynamic web project is published in an OSGi application, it is actually converted to an OSGi web bundle by the server at run time.

The OSGi Alliance consists of a group of many different contributors that govern and maintain the OSGi specifications.

It might remotely expose any of its Blueprint-configured OSGi services as SCA services and configure remote bindings for these services.

Applications built to run on Lotus Expeditor must provide information to the platform about their contents through the OSGi Manifest file.

Each module that forms a part of the Application-Content, along with all its calculated dependencies, is deployed as an OSGi bundle.

This purpose of this article is to help you understand how to convert your existing Java EE applications into OSGi-based applications.

A similar solution needs to be implemented for the Felix-specific implementation; since as yet, there's no standard for OSGi command shells.

OSGi has been a quite positive progression of the last 3 months.

The persistence configuration file, persistence. xml, can be located anywhere in an OSGi bundle.

Bundle-Version becomes particularly important if an OSGi application becomes complex and many versions exist of a specific bundle.

In fact, some of the successes that OSGi brings to a project is purely the enforced modularity constraints between modules.

An SCA component implementation provided by an OSGi application has an SCA component type of implementation. osgiapp.

OSGi provides among other things the component model, a deployment mechanism for modules and a clean class loading system.

Runtime systems (like Jigsaw or OSGi) could then use this information in validating the set of installed modules and their dependencies.

It also adds OSGi and Felix dependencies to the project, which are needed for the add-on to run inside the Roo shell.

A broader discussion of the scenarios and patterns for using OSGi and SCA together are beyond the scope of this article.

All OSGi services are automatically registered in JNDI and can be accessed in a manner familiar to Java EE components.

At present Solstice is deployed as a WAR file, but it will soon become a pure OSGi stack with no application server required.

The redeployment features of most servlet containers, application servers and OSGi implementations each work along the same lines.

Ideally, interfaces in OSGi applications should be in separate bundles (projects) from the implementation classes.

The OSGi people just get upset that the standard baseline is not their implementation, and actually takes other things into consideration.

It is a simple OSGi bundle that does not make use of any enterprise features.

Among the several different attempts to design a module system for Java, the best known is OSGi.

Whilst Jetty is now a set of valid OSGi bundles (with well-defined dependencies), it can still be run outside of an OSGi runtime.

For the last few releases, PDE has provided support for developing OSGi standalone applications.

Because OSGi bundles are modular and easy to deploy, you can make updates without having to restart an application.

DS components needs no OSGi interfaces, and as such, can be mocked for testing or used in other inversion of control patterns like Spring.

Some architecture changes were also made to allow Mule to be loaded from an OSGi container.

This is likely to help the creation of secure OSGi platforms which can lock down the installation of unsigned bundles.

Eclipse RCP allows for the modularization of classes and resources into jar files called plugins which are a superset of OSGi bundles.

Note that Guice can be used in OSGi without Sisu; the 3. 0 release provides standard OSGi interoperation out of the box.

Solstice is the first framework to integrate Flex and OSGi in a single out-of-the-box package.

OSGi provides a robust integrated environment where bundles can be published as services and exported for other bundles to use.

In the world of OSGi, we do not always know when another service is available, and, as a result, we need to account for this.

When the installation is complete, the utility component is deployed as an OSGi bundle and the Web component is deployed as a WAB.

Most of the time this can be null, but it's possible to supply both OSGi-specific and general properties about the URLs.

The call for speakers is still open; if you'd be interested in giving an OSGi talk, then submit a proposal.

Multiple versions of classes can be loaded simultaneously in the same application using standard OSGi mechanisms.

The Device Manager database stores URLs for locating software packages and OSGi bundles, as well as other software information.

This lookup is unambiguous because OSGi applications are isolated and Blether defines only a single persistence unit.

When Eclipse opens the manifest file in design mode, select the Dependencies tab and add org. osgi. compendium as the "Required Plug-ins" .

These services will allow enterprise applications to run inside an OSGi environment instead of needing a whole JEE stack.

Frameworks like OSGi give you these variation mechanisms out of the box.

The EEG was created in December by the OSGi Board, and held its initial meeting at the end of January in Dublin, Ireland.

Jim: OSGi a great technology and BEA is a strong supporter.

This dependency injection model also enables unit tests to be run outside either a Java EE or OSGi runtime.

The processing of the metadata and the run time enforcement of the visibility rules are provided by the OSGi framework resolver.

The Java EE web module, EmployeeListWeb, can be added to the OSGi application manifest as a dynamic web project.

Enterprise Web application developers looking for reliable and proven modularity technology are increasingly turning to OSGi.

Graham Charters: I did a survey at the OSGi Community Event that pretty much confirmed what I thought.

The OSGi Alliance is the standards body responsible for the specification of flexible modularization technology for Java.

OSGi helps us solve this type of problem through the ability to dynamically provision and version software components (bundles).

Blueprint is integrated with the OSGi service registry, enabling managed instances to transparently use, or be exposed as, OSGi services.

Similar and complementary projects and products to Aries provide many different ways of building applications that use OSGi technologies.

The Blueprint container can be retrieved from (not surprisingly) the OSGi service registry.

But it goes much further than this and solves a number of additional problems common in enterprise environments.

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

OSGi is fast gaining momentum as a framework for developing and deploying modular reusable Java programs.

A large number of services and libraries have been developed for the OSGi framework.

You enable modular service-oriented components and features with OSGi technology in a couple of ways.

An OSGi bundle that acts as a bridge between the Web services bundle and the resource bundle.

ServiceMix is built using OSGi components and offers the ability to use OSGi technologies with Service-Oriented Architecture (SOA).

You are expected to provide the implementation of the service object as an OSGi bundle.

Nuxeo EP is built on top of OSGi, comprising a set of around 120 bundles containing components, services and extension points.

Applications can be designed for extensibility and dynamic update through the use of OSGi services.

It's clear that OSGi adoption in large server systems is becoming commonplace, and that's starting to filter down.

The OSGi support enables hybrid application development to leverage the benefits of OSGi modularity and Java EE programming model.

At the other end of the OSGi spectrum lies the embedded and micro devices.

With these changes, the persistence bundle and core application logic is in good (OSGi) shape.

Listing 2 shows a complete application manifest for a simple OSGi application.

Different OSGi applications can therefore utilize different versions of the same bundle.

But we are also interested in the potential of the OSGi programming model for meeting basic enterprise IT requirements.

Understanding the programming framework of OSGi is the basis for designing and implementing SMF-based applications.

But so far the answer is that we are definitely not going to be doing this with OSGi.

Replaceability: OSGi permits a module to be shutdown and replaced at run time.

In the course of this exercise, you will transform it into an OSGi application and then gradually remove the dependency on Spring.

We accomplish this complete decoupling of components by having the plug-ins Extension Registry aware and providing an OSGi service.

This article also includes detailed guidance on best practices for running and migrating Spring-based applications to OSGi.

However, to add a dynamic web project as a JEE module to an OSGi application, follow these steps.

OSGi also provides a Java Virtual Machine (JVM)-level service registry that bundles can use to publish, discover, and bind to services.

OSGi modularity semantics are honored in the project build paths, providing an environment which supports a modular design.

PDE provides Equinox support out of the box, and also provides extension points for other OSGi frameworks such as Knopflerfish and Felix.

The persistence bundle makes use of another standard feature of enterprise OSGi, JPA integration, to take advantage of managed persistence.

When you create an OSGi service or a Web service, the common practice is to create an interface and an implementation class.

There are a number of ways to get started with deploying your first OSGi application to WebSphere Application Server.

OSGi defines additional metadata in the JAR's MANIFEST. MF to indicate required dependencies on a per-package basis.

Groovy Eclipse comes with an embedded Groovy runtime library that is split off as its own Eclipse plugin (or in OSGi parlance, bundle).

Initially, OSGi was targeted at home automation and residential gateway devices.

Refer to the OSGi Service Platform specification (see Resources) for more information about the manifest file format and syntax.

OSGi Alliance (See Resources) publishes the specifications for the module system.

In general, there are few changes that need to be made to the persistence. xml files to make them work in an OSGi framework.

One example of a common product that uses OSGi technology is the Eclipse IDE.

Will OSGi modules be able to interoperate cleanly with JSR 277 modules?

It packages multiple enterprise Java application frameworks together as OSGi bundles.

See Developing enterprise OSGi applications for WebSphere Application Server for more information on OSGi applications.

In the meantime we'll actively seek ways in which to interoperate with other module systems, and in particular with OSGi.

You have done the work of adding necessary code and configurations to make your OSGi service a Web service.

Effectively, OSGi technology is the missing modularity layer for the Java platform.

One is for the OSGi framework into which the blog sample application is installed and one is the server-wide shared framework.

Over recent months, the Open Source Gateway Initiative (OSGi) has been gaining attention in the application server technology space.

OSGi is a technology that you can use to build Java services and modules that are truly modular, pluggable components.

Hopefully Virgo will increase adoption and be more attractive to participation and contributions from other industry companies.

Secure Development Across Teams - The OSGi microkernel style inforces rules to keep components and extensions isolated and controlled.

Are the events sent via the OSGi pub-sub mechanism synchronous or asynchronous?

By providing a filter, you're telling the OSGi service registry to only notify you of state changes in the specified service.

InfoQ: Is there any plans on releasing this as a formal standard document through OSGi or another organisation?

Using this framework, one can develop and deploy a web service as an OSGi bundle.

Promote OSGi to a first class Tuscany runtime environment.

This week sees the publication of OSGi and Equinox, the first in a new series of Eclipse RunTime books.

If you use dynamic class loading (class. forName) then these often need to be remediated, but can map to OSGi services.

OSGi and other modular systems are the key to this, and our first step into OSGi was a big deal for us and our users.

See documentation for assembling and deploying OSGi components in SCA composites for more.

All the bundles deployed in an OSGi container run in one JVM.

Besides those OSGi defined services, bundle vendors can develop custom services.

Create an OSGi bundle, including Java interfaces and classes, a manifest file, and resource files.

This is an OSGi-specific piece of code which is invoked when the bundle is started, like a per-bundle main method.

Using resource references is a standard way to obtain centrally managed and administered Java objects in both Java EE and OSGi environments.

See administrative tasks for deploying OSGi applications for details.

Eclipse should now restart the OSGi framework, install the fourth bundle (DictionaryServiceV2) and start all four bundles.

You can now initialize product definitions from OSGi launch configurations.

Aniszczyk pointed out the PDE eases OSGi development by managing the classpath and by leveraging the existing Eclipse development toolset.

OSGi is a specification of a service platform.

There are various OSGi commands available in the Roo shell, which you can see by typing help osgi, as shown in Listing 1.

Within WAS V 8 existing components can be exposed as SCA components inside OSGi applications.

Composing MANIFEST. MF needs to comply with the rules defined in OSGi specification.

Eclipse plug-ins use OSGi technology for its benefits in building modular applications.

Standard Management of Company Projects - If all projects are broken down into OSGi components they are easily reused.

This allows developers to design modular application architectures on top of a lower-level modularity system such as OSGi.

Refactoring for E4 may be back-ported to the next Eclipse 3. 7, especially accessing via OSGi services.

OSGi provides a simple means to hook classloading in a global fashion.

We'll describe how to create bundles, how to install them into an OSGi engine and how to set up (versioned) dependencies between bundles.

Some JPA 2. 0 sample code is also presented should you wish to experiment with a new OSGi application.

ML: How is the work within the OSGi committee progressing?

OSGi throws runtime errors if the imports and exports aren't explicitly declared.

We're using well-known technologies like Java and Osgi to create a framework to bring simplicity for both telecom operators and partners.

You can temporarily wire to the OSGi registry from Spring via the osgi: service namespace.

The Eclipse IDE uses a subset of OSGi centered around modularization and bundle life cycle.

Bundles can also be added to OSGi applications in the new OSGi application wizard.

Lastly, IntelliJ 9 has been released; and both the community edition and commercial edition have support for building OSGi applications.

Some open source projects package their Java classes in OSGi bundle-compliant JARs.

Alternatively, the BundleContext of the Web bundle is available from the servlet context via the osgi-bundlecontext attribute.

SpringSource is also working with the OSGi Alliance to continue evolving the OSGi standard.

OSGi is a means for specifying a scope of encapsulation so that fits naturally into the module decomposition view.

One alternate way is the services framework of the OSGi platform.

Data Capture runs on OSGi to support the distributed runtime environment.

The OSGi specification defines a unit of modularization called a bundle.

The custom service factory class should implement the OSGi ServiceFactory interface.

Now I'll create a more useful program that monitors the life cycle of bundles and services within the OSGi framework.

With the OSGi console running, you can see the status of the modules by typing ss at the console.

Next we need to specify that the osgi compendium bundle as the required bundle to the dosgi bundle.

Select OK to confirm the conversion from a JEE web project to an OSGi bundle.

With OSGi, you can update the bundles dynamically at run time whenever there's a code change.

It's not an issue with OSGi per se, but with modularity as a concept.

Data capture runs on OSGi to support the distributed run time environment.

OSGi naturally offers a compelling choice for this need.

Specifications describe the behaviour of how the OSGi runtime works; the current release is OSGi R4. 2 (as covered by InfoQ previously).

The bundle is the delivery and development unit of OSGi applications.

Eclipse should now start its internal OSGi framework (Equinox) install and start the three bundles in the workspace.

OSGI, knowing to use you next time can be when. . .

Select OK to confirm the conversion from JEE web project to an OSGi bundle.

As with JDBC, OSGi is a specification (currently release 4. 2) which has multiple open-source (and commercial) implementations.

STS allows to deploy WAR applications, OSGi bundle and PAR projects to dm and tc Server running in the Amazon EC2 cloud.

The core micro broker bundle exposes a BrokerFactory service to the OSGI runtime that bundles can track using the OSGI Service Tracker.

We will also register the plug-in to be an OSGi service.

This is a wsadmin client application that provides a remote OSGi console for the specified application server.

The first few migration stages described in this article rely on using the default OSGi application behaviour.

In all cases, you need to package the OSGi application in a format that can be deployed.

Eclipse uses OSGi as its modularity mechanism for plugins.

OSGi If JSR 277's JAM module system is an unsuitable foundation for modularizing the JDK, what about the OSGi Framework?

Two open source projects providing implementations of the OSGi enterprise specification were started within the last year.

In OGSi, each bundle has its own class loader.

If Mule should integtate OSGi or some other way to easily update integration flows that would be a big plus.

Contract: OSGi provides a good match to the contract.

InfoQ: Using OSGi for server side application is something ubiquitous these days.

Select OK to confirm the conversion from JPA project to OSGi bundle.

Sun voted against JSR 291, which passed anyway, making OSGi officially part of JSE.

This has previously been possible with Pax Web, but this brings a standard so that any OSGi runtime can be used.

Each bundle must implement the OSGi BundleActivator interface so that it can be controlled by the SMF runtime throughout its life cycle.

In Import Services, fill in org. osgi. service. HttpService, as this is the only service HttpLog will visit in runtime.

Next download cxf-dosgi single bundle distribution and the osgi compendium bundle.

Then you package these components as OSGi bundles.

See Best practices for developing and working with OSGi applications, #4.

This defines the OSGi semantics of enterprise Java technologies such as transactions, persistence, and Web components.

This thesis also works on the other issues of OSGi such as service dependence, automatic service deployment and service cache management.

OSGi also gives you the opportunity to do a much better job of versioning in the enterprise environment.

If you are using MBeans, then there's a simple mapping strategy to OSGi services.

Listed here are some related technologies that you can use to build, manage, and distribute OSGi components into applications.

The feature pack actually consists of two installable features: the OSGi application feature and the JPA 2. 0 feature.

However, it makes minimal use of the service support OSGi provides.

OSGi has given a new dimension to the way JAR bundles are built and managed.

OSGi is a runtime dynamic module system for Java.

It is expected that the final version will be released in time for OSGi DevCon, co-hosted with EclipseCon, in March this year.

Impala is not currently OSGi compliant although this is also planned for the first full release.

Equinox, the OSGi runtime has been updated to support the new OSGi 4. 3 features (including generics), as covered previously.

At its core, OSGi is a component and service model, as illustrated in Figure 1.

The 1. 0 release provides a solid foundation for creating Spring-powered OSGi based applications.

Create a new configuration in the OSGi Framework folder called demo_dosgi.

Last summer I received an invitation for IONA to attend the OSGi Enterprise Workshop on September 11, 2006.

Leveraging OSGi where it makes sense.

Roo has a special project called wrapping that can convert normal JARs into OSGi JARs.

We are using the OSGi APIs to tell us when this service comes and goes, so we can properly register our extensions.

We will use this servlet container outside the OSGi container (Eclipse) to install and run our service clients.

Each OSGi container provides a different default target start level; for Equinox, the default is 6, whilst for Felix it is 1.

Now that the data source is set up in the WebSphere server, the OSGi bundle needs to be set up to access it.

However, once you move to OSGi, this migration is enforced at both compile-time and run-time.

OSGi is a dynamic module system for Java.

What do you think is the most noteworthy part of OSGi 4. 2?

You can view the status of the add-on using the osgi ps command.

This work will continue in Spring 2. 1, with the packaging of Spring's JAR files as OSGi bundles.

This is an OSGi best practice that keeps couplings loose.

The neat thing about RAP is that you write Ajax applications in Java and use the Eclipse component model based on OSGi.

This means it is very clear which packages are private and OSGi enforces this.

I think it is a telling sign that we implemented FTP integration before OSGi.

Geronimo 3 has also updated its kernel to use OSGi, based on the Apache Karaf OSGi runtime, and supports the Aries programming model.

OSGi DevCon was focussed on a lot of modularity-related subjects; mostly the Enterprise OSGi noted above, but also a Cloud Workshop.