Recommended
More Related Content
Similar to OSGi Puzzlers: Overlapping Concerns and Dynamic Service Replacement
Similar to OSGi Puzzlers: Overlapping Concerns and Dynamic Service Replacement (20)
More from mfrancis
More from mfrancis (20)
Recently uploaded
Recently uploaded (20)
OSGi Puzzlers: Overlapping Concerns and Dynamic Service Replacement
- 1. OSGi Puzzlers Neil Bartlett and Peter Kriens
- 3. What Does it Print? MyService P1 P2 Example Component NOW STOP BUNDLE P1... MyService
- 5. WTF? OSGi Compendium, section 112.5.10 Dynamic Service Replacement “SCR must first bind a replacement target service and then unbind the outgoing service” (emphasis added)
- 6. Beware this Pattern @Component public class ExampleComponent { private MyService svc; @Reference(dynamic = true) public void setMyService(MyService svc) { this.svc = svc; } public void unsetMyService(MyService svc) { this.svc = null; // OOOPS! } }
- 7. Better... @Component public class ExampleComponent { private MyService svc; @Reference(dynamic = true) public synchronized void setMyService(MyService svc) { this.svc = svc; } public synchronized void unsetMyService(MyService svc) { if (this.svc == svc) this.svc = null; } }
- 8. Even Better... @Component public class ExampleComponent { private final AtomicReference<MyService> svcRef = new AtomicReference<>(); @Reference(dynamic = true) public void setMyService(MyService svc) { svcRef.set(svc); } public void unsetMyService(MyService svc) { svcRef.compareAndSet(svc, null); } }
- 10. What Does It Print? A. 0,1,2,3,4,5,6,7,8,9,... B. 1, C. 1,2,3,4,5,6,7,8,9,.... D. NullPointerException
- 11. What Does It Print? A. 0,1,2,3,4,5,6,7,8,9,... B. 1, C. 1,2,3,4,5,6,7,8,9,.... D. NullPointerException
- 12. WTF?
- 13. Blacklisting EventHandlers have to return quickly If they don’t... BLACKLIST! No more events for you. Humans are slow and stooopid. Turn off blacklisting, OR use printf-style debugging
- 14. You Gotta Start Me Up...
- 15. What Does It Print? A. “Constructed...Started.” B. “Constructed...” C. Nothing D. IllegalAccessException E. “Started.”
- 16. What Does It Print? A. “Constructed...Started.” B. “Constructed...” C. Nothing D. IllegalAccessException E. “Started.”
- 17. WTF? DS Services are Lazy Not an error... just waiting for a consumer!
- 18. REMEMBER: OSGi is Your Friend!