Here are the things every Java developer working on OSGi-based middleware must know, IMO:
Essentials:
- Design-by-Contract & SOA
- Component/Package Versioning
- OSGi Bundle Lifecycle
- Bundle Manifest directives
- Core OSGi services
- Spring DM (especially for simplification of the usage of OSGi services and writing in-container tests)
- BND tool (I cannot think of a better way to create the OSGi manifest files than this)
- Basics of classloading in OSGi
Advanced Topics:
- HTTP Server options in OSGi (OSGi HTTP Service, HTTP Servlet Bridge, etc.)
- OSGi “uses” directive and the “type leakage” problem
- OSGi Services vs. Extensions/Extension points
- Service Trackers
- Concurrency gotchas in OSGi
- The Whiteboard pattern
- The “Extender bundle pattern”
- OSGi Declarative Services and Configuration Admin Service
