Many people are drawn into OSGi because it provides class loaders on steroids, however, one of the often overlooked feature of OSGi is the Service Registry and the (µ)service model.

µServices provide a much more powerful alternative to the traditional Java factories and listeners in your code or xml, which are the usual culprits for class loading headaches. Alas, you need to migrate your application to OSGi first in order to take advantage of µServices which would make it so much easier to migrate your application to OSGi in the first place.

The idea of PojoSR (a.k.a OSGi Lite) is to remedy this situation by providing OSGi without the module layer. PojoSR is based on Apache Felix and runs in any standard Java environment: from the class path, inside a WAR, wherever your current Java runs because it never touches a class loader. It allows any application built in Java to reap the benefits of service-based modularity without first having to rid existing code of any class loader tricks. This approach also allows, many existing bundles work out of the box – just by adding them to the class path (PojoSR will detect bundles on the class path and execute their activators).

It works so well that OSGi is thinking of standardizing the approach. This talk will show you how you can take advantage of µServices using PojoSR to modularize and OSGi’fy an existing application.