Google Web Toolkit on OSGi, step by step
Angelo van der Sijpt of Luminis has just published a simple, step-by-step tutorial to use GWT (Google Web Toolkit) in a OSGi application.
Google Web Toolkit is cool, and so is OSGi. However, creating a web application that can use GWT services is not that easy. By the end of this tutorial, you will have created a GWT project that delivers a usable jar. If you’re impatient, skip to the end for the downloadable Eclipse project.
Read the tutorial on the Luminis blog.
Neil Bartlett on OSGi
This interview, conducted at QCon 2009, covers a wide range of topics beginning with a definition of OSGi and ending with an audience question about integrating OSGi into legacy application servers (like Websphere). In between Neil answers questions about the origins and evolution of OSGi, how OSGi compares to .Net modularization, and constraints on the use of certain Java libraries.
Check the interview on InfoQ.
The 5 presentations you missed at OSGi Devcon
Last week’s OSGi DevCon Europe has offered a huge choice of good presentations. In case you missed them, here is my selection:
Blueprint Services, by Guilliame Nodet
Dynamic Deployment with Apache ACE, by Marcel Offermans
Managing Change, by Neil Bartlett and Mirko Jahn
Distributed Services – OSGi 4.2 and possible future enhancements, by David Bosschaert and Marc Schaaf
From Distributed to Pervasive OSGi, by Jan s. Rellermeyer
Android on OSGi, Akquinet’s solution
Another presentation of OSGi on Android, this time from Akquinet:
OSGi on Android, the ProSyst solution
OSGi on Androids is one of the hottest topics in OSGi-land. After EZDroid and Felix4Android, the Mobile OSGi blog presents Prosyst‘s solution:
Pursuing the goal to create a value adding OSGi based stack for Android, ProSyst recently releases the first version of the stack. It works on all Android 1.5 (Cupcake) compliant devices.
Read the complete article on the Mobile OSGi blog.
Prosyst “Mobile OSGi on Android” presentation is also available on Slideshare:
Logging in OSGi applications
Valery Abu-Eid of DynamicJava has posted a detailed article explaining how to use effectively the OSGi Log Service.
Observing different approaches for logging OSGi-based applications for few months, I came across different articles on the topic. Although they explain how to use the OSGi Log Service pretty well, all in all, I consider the general approach for logging OSGi-based applications using OSGi Log Service is too complex. The complexity is driven by the fact that OSGi is a dynamic environment, and OSGi Log Service, like any other service, could become available or unavailable at runtime. Sure, these concerns need to be addressed, but my point here is that this should not be the responsibility of the developer.
Read the complete article here.
Remote Declarative OSGi Services with ECF
Bryant Hunt has just published a detailed tutorial to start using the distributed OSGi specification using the Eclipse Communication Framework.
My last post on OSGi services showed how you can dynamically configure OSGi services using the ConfigurationAdmin service. I used an example where I configured a service to create a JDBC connection. JDBC connections are often made on a server, and it would be nice to be able to do your configuration remotely. This post will show you how you can use RFC 119 to make remote OSGi service calls to configure the JDBC connection on a server.
Read the complete tutorial on Brian’s blog.
Web Frameworks on OSGi Matrix
The RFC66 – OSGi Web Container is currently under discussion, but it is already possible to deploy web applications in any OSGi container using the great Pax Web and Pax Web War Extender (the two projects will be merged soon).
But does this mean that it is also possible to use any Java Web Framework with OSGi?
Unfortunately that’s not the case. On the contrary, many of the most famous web frameworks internally use some “hacks” or classloading trick preventing them to work out of the box in a OSGi container.
The following table (under-construction!) tries to summarize the situation:
| Framework | Situation | References |
| Apache Wicket | Pax Wicket is an OSGi-based extension to the Wicket framework. Whereas a typical Wicket application requires that all component wiring be done at compile time, this extension allows you to model the Wicket application, and move those model parts around and not be resolved until request time. You can add and remove parts of the Wicket application without restarting the application, simply by loading and unloading OSGi bundles. New sections can be added, and if properly prepared, menu items for those sections can be added to all existing pages. |
Pax Wicket |
| Apache Struts | A full OSGi scenario seems not to be supported yet, but there is an OSGi Plugin providing support for starting an instance of Apache Felix inside a web application, and scanning installed bundles for Struts configuration. An admin bundle is also provided. | Struts OSGi Plugin |
| Stripes | No successful use cases reported. Issues with dynamic discovery of ActionBeans | Email thread on stripes-users |
| Spring MVC | Reported to work on OSGi | |
| Google Web Toolkit | Reported to work | gwt-in-osgi |
| Apache Tapestry | Success reported, even if it’s not clear if it’s a full OSGi scenario. | Tapestry-OSGi |
| Apache Sling | It is an open source Web framework for the Java platform designed to create content-centric applications on top of a JSR-170-compliant (aka JCR) content repository; it is specifically designed to run on a OSGi container. |
As you can see, that’s only a first draft of the Web Framework on OSGi matrix. Have you had any success using a popular Web Framework in a OSGi container? Please add a comment to this post sharing you experience!
EJB as OSGi Service on Glassfish
After the first installment, Developing Hybrid (OSGi + Java EE) applications in GlassFish, Sahoo presents in his blog how to access an EJB as a OSGi service on Glassfish.
The OSGi Look 