Le blog de Fabien DUMINY

Incoming events in the group :
• February 2009 : It’s the first birthday of the group. On this occasion, there will have quickies (15 minutes presentations)
• Call for blogger (I have asked to add my blog and I am waiting the answer)
• 4 November : conference on GWT (I intent to come)
• 12 November : Open source exchange

• It’s possible to avoid collisions between different versions of the same library by repackaging them (changing package names) : It’s was has been done with tomcat which includes its own version of commons-dbcp (see reference)

Comparison of OSGI and JCP:

• To become a member :
  • JCP : free
  • OSGI : 20 000 €
• TCK (conformity tests) :
  • JCP : accessible especially to the open source community
  • OSGI : less easily accessible

OSGI and the JSR :

• JSR 291 : created by the OSGI community to integrate in JAVA SE a dynamic component model based on OSGI
• JSR 277 : has for goal to integrate the notion of modules in JAVA. This might not succeed and be merged with JSR 291
• Spring DM (Dynamic Modules)
  • will probably become the next OSGI standard because it seems to be welcomed by the JAVA community
  • is normalizing its main ideas with the RFC 124. It seems to threaten the notion of «declarative service » (OSGI v4), which is a layer on top of OSGI targeting the declaration of imported and exported services by the bundle.

OSGI and the java applications :

• Apache geronimo : the jars are OSGIfied but are not inside an OSGI container
• Apache felix
  • implementation of an OSGI container by the apache community
  • allows to generate OSGI manifests with Maven
• eclipse : based on OSGI since version 3.0
  • equinoxe : implementation of an OSGI container for eclipse
  • eclipse RAP (Rich Ajax Platform) : equinoxe in a web application
  • eclipse BIRT : example of a web application with its own OSGI container
• Websphere 6.1 : full OSGI. It doesn’t expose OSGI APIs to web applications.
• Service Mix, an ESB (Enterprise Service Bus) : manages (among others) the autorefresh of added/removed OSGI services.
• PAX : open source project wrapping third party libraries with OSGI format. It’s compound of (among others) :
  • PAX Logging : logging libraries like log4j
  • PAX Construct : Maven plugin which allows to manage OSGI bundles
• JUnit : it’s mono ClassLoader and that’s a problem with OSGI
• Spring DM : probably the future OSGI standard

Remarks on OSGI :

• One ClassLoader per bundle
• Class.forName : to avoid with OSGI as much as possible. See the discussion on that subject.
• The OSGI ServiceTracker can see many service (JAVA interface) implementations
• Problem : How to add a dynamic dependency ? Solution: attach a « bundle fragment » by adding « Bundle-Host: bundle_name» in the manifest

Various notes :

• The manifest file is limited to 76 columns (strange limit …)
• Eclipse feature : it’s a set of plugins, for example a functional domain in an enterprise application

To learn more :

• Download the presentation (in french)
• See the JUGgers blogs (section “Post (blog) sur la présentation”, in french)