RFC 193: OSGi CDI

CDI (Context and Dependency Injection) is the standardised dependency injection model in Java EE 6. The CDI-OSGi specification brings CDI to OSGi to publish and consume OSGi services.

The CDI-OSGi specification (RFC-193) introduces a way to use CDI in OSGi. This brings the ease-of-use of CDI to OSGi, and more importantly, brings the OSGi and Java EE worlds closer together. It allows seamless integration between standard CDI code and the OSGi service model. Other features include sending and observing EventAdmin events using CDI events. In this presentation you will get an overview of the possibilities of this new specification, including some in-depth discussion of difficulties in integrating the OSGi service lifecycle with CDI.

The speaker is a member of the OSGi Enterprise Expert Group and works on the CDI-OSGi specification.

Transcript

1. RFC 193 - OSGi CDI Bridging the OSGi and Java EE worlds
2. Paul Bakker Architect at Luminis Technologies @pbakker #CDIOSGI
3. What is CDI Contexts and Dependency Injection Standardized dependency injection model in Java EE
4. Bringing CDI to OSGi Services RFC 193 OSGi-CDI
5. Why care!? We have DS, Blueprint, ...
6. Publishing OSGi Services @OSGiComponent Instructs CDI to publish to the Service Registry
7. Publishing OSGi Services By default all interfaces are published
8. Publishing OSGi Services Optionally specify the interfaces explicitly
9. Publishing OSGi Services OSGi Service Registry CDI BeanManager OSGi Service CDI bean Lookup Register @OSGiComponent
10. In CDI every class that is injected somewhere is a managed Why the @OSGiComponent qualifier? We can’t know this up front in an OSGi application
11. Scopes CDI has the concept of scopes Default scope Request Conversation Session Singleton
12. @RequestScoped MyService @RequestScoped BeanA @RequestScoped BeanB @Inject @Inject Request 1 @RequestScoped MyService @RequestScoped BeanA @Inject Request 2 Scopes in CDI
13. But how to map this to OSGi!? OSGi services are effectively singletons....
14. Default scope Request Conversation Session Singleton Scopes in OSGi CDI OSGi services do not support scopes However, RFC 195 might be helpful Prototype Service Scope
15. Prototype scope Create multiple service instances per bundle
16. @Inject plain CDI beans Only within the same bundle!
17. @Inject OSGi Services
18. @Inject OSGi Services OSGi Service Registry CDI BeanManager OSGi Service CDI bean Registers Lookup @Inject @OSGiService
19. What about service dynamics!??
20. Null object pattern If MyService is not available, a null proxy is injected Injection happens every time MyService is registered / deregistered
21. Working with null proxies can be quite annoying
22. Required dependencies If my dependencies are not available, neither am I
23. Required dependencies B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = true) Dependency graph
24. Required dependencies B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = true) If C is deregistered, so are B and A
25. Required dependencies B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = true) If C is deregistered, so are B and A
26. Required dependencies B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = true) If C becomes available, so are B and A
27. Required dependencies B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = true) If C becomes available, so are B and A
28. Required dependencies If C is deregistered, B and A don’t care B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = false) C is not required...
29. Required dependencies If C is deregistered, B and A don’t care B A @Inject @OSGiService(required = true) C @Inject @OSGiService(required = false) C is not required...
30. Required dependencies If C is deregistered, B and A don’t care B is not required, C is B A @Inject @OSGiService(required = false) C @Inject @OSGiService(required = true)
31. Required dependencies If C is deregistered, B and A don’t care B is not required, C is B A @Inject @OSGiService(required = false) C @Inject @OSGiService(required = true)
32. Injection callbacks For when a single service just isn’t enough
33. Using standard CDI events Event qualifier Injection callbacks
34. Service filters with CDI qualifiers (somekey=somevalue)
35. Service filters with CDI qualifiers &((somekey=somevalue) (someotherkey=somevalue)) AND
36. Required config The component will only become available after the configuration object is found
37. Event admin EventAdmin CDI-OSGi bridge Observer EventAdmin EventHandler CDI bean Send EventAdmin event using CDI events Notify Publish @Inject @EventAdmin Event event
38. Sending events using CDI events Sends event to the “demo” topic
39. Event admin CDI-OSGi bridge Observer EventAdmin CDI event listener EventAdmin producer Listener to EventAdmin events using CDI observers @Observes @EventAdmin Publish Notify
40. Receiving events using CDI events Listens to the “demo” topic
41. Life-cycle callbacks
42. Bundle Context injection
43. Setting up CDI Enable-­‐CDI:  1.0 MANIFEST.MF
44. What’s still missing? Contexts and Dependency Injection Standardized dependency injection model in Java EE Interceptors on services CDI extensions
45. Call for help & feedback! @pbakker paul.bakker@luminis.eu