The interceptor itself is a Java POJO and this screencast goes into what it takes to develop the annotation, build the application and create an OSGi bundle, and finally install and start the interceptor in the Felix runtime. Interceptors are started and stopped independent of the application. Details on the Java
@Interceptor annotation are available from this wiki page.
Project Fuji was announced at this past JavaOne and is the next generation OpenESB architecture based on GlassFish v3, OSGi, and JBI. It also features a top-down development language, IFL (Integration Flow Language) briefly shown in a previous screencast. Keep also an eye on the GlassFish Podcast for a Project Fuji presentation by tech lead Andreas Egloff. Previous entries on the topic are marked with the "Fuji" tag.