Slides from the JFall '09 session on OSGi Software Architecture by Marcel Offermans and Jeroen van Grondelle.

1. Beyond
OSGi Software
Architecture
Jeroen van Grondelle
Marcel Offermans
11 november - JFall 2009

2. About Us
Marcel Offermans Jeroen van Grondelle

3. Lean Development
Service Interfaces
OSGi based Apps
Service Creation Patterns

4. Lean Development
Part 1

5. Anticipate Change
Yes, there WILL be new
requirements...

6. "Non-Functionals“
Great functionality! And can you do that, in a ... way.
Based on Luke Hohmann's book Beyond Software Architecture

7. Anticipate, don’t
over dimension
Do not try to support the things now
that MIGHT be required next...

8. No decision is irreversible, but some
are VERY expensive to reverse...

9. Service Interfaces that
help you Change
Part 2

10. Behavior Only
Do NOT disclose parameters and implementation details.
Do NOT shape a Service after your rst/only implementation.
This is NOT Object Orientation. Or is it... ;-)

11. Scale Invariance
Service Interface should NOT re ect the scale
your ( rst) implementation will support.

12. Decoupling
If your implementations require other services,
access these services through interfaces only.

13. Think BIG
act small!
Your service interface should be future proof,
your implementation should t your current needs.
Keep many possible implementations
(functionality, scale) in mind when designing interfaces.

14. Service Oriented Apps
using OSGi
Part 3

15. OSGi Recap
Service
Log Store Prefs
publish publish
publish use
use use
Bundle Bundle Bundle Bundle
install Life Cycle
installed
Service start start starting
Bundle Bundle Bundle Life Cycle resolved active
Module
end uninstall stopping stop
Security
uninstalled
OSGi framework
Java Virtual Machine
Module
Bundle Bundle Bundle Bundle
imports exports imports
exports exports exports
org.apache.util 1.0 org.apache.db 1.4
org.apache.log 2.3 org.apache.util 1.1

16. Container Style
Development
Application consists of
interdependent Services
Public Services are accessed
through UI/SOAP/JMS/...

17. Be a Good Host
Offer facilities to
your components
OSGi Compendium is a
Catalog of generic Facilities
Add your own to the container if needed

18. Deploy Everything
Not just code!
Content
Configurations
Testcases
Work

19. Inversion of Control
Use declarative Lifecycle and
Dependency Management
Develop POJO’s
Delegate injection

20. Add Chemistry
Deployed services react
on each other
Resulting in behavior
and new services
Define these reactions in terms of
life cycle and dependencies

21. Patterns for Creating
Service Graphs
Part 4

22. Singleton Services
Singleton
Document
Repository
get() Storage
getVersions() requires
get(version)
store(Document)
Bind Logic in a Single Instance

23. Singleton Services
class Activator {
public void init(context, manager) {
manager.add(
createService()
.setInterface(DocumentRepository.class.getName())
(Pseudo)Code
.setImplementation(DocumentRepositoryImpl.class)
.add(
createServiceDependency()
.setService(Storage.class)));
}
}

24. Aspect Services
Aspect
Repository Cache Repository
get() get()
getVersions() intercepts getVersions()
get(version) get(version)
store(Document) store(Document)
Transparently inject an interceptor service
"in front of" all services matching a lter

25. Aspect Services
class Activator {
public void init(context, manager) {
manager.add(
createAspectService(
DocumentRepository.class,
DocumentRepositoryCache.class,
10));
}
}

26. Adapter Services
Adapter
Repository Cache Repository Cache
Manageable get()
getCacheHits() getVersions()
adapts
setSize() get(version)
setTTL() store(Document)
flush()
Start an instance of the adapter service for any
"adaptee" service matching a lter

27. Adapter Services
class Activator {
public void init(context, manager) {
manager.add(
createAdapterService(
Manageable.class,
DocumentRepositoryCache.class,
DocumentRepositoryCacheManageable.class));
}
}

28. Resource Adapters
Resource
Audio Track Adapter
play() MP3
adapts
pause() File
stop()
Start an instance of a Resource Driven Service for all
resources matching a lter
Resources: File(system) abstraction, access by InputStream

29. Resource Adapters
class Activator {
public void init(context, manager) {
manager.add(
createResourceAdapterService(
"(extension=mp3)",
AudioTrack.class,
MP3AudioTrack.class));
}
}

30. Dependency
Management & OSGi
Not standard OSGi, a number of extensions available.
Felix Dependency Manager implements these patterns.

31. Lean Development
Service Interfaces
OSGi based Apps
Service Creation Patterns

32. Questions?
Marcel Offermans Jeroen van Grondelle
marcel.offermans@luminis.nl j.vangrondelle@beinformed.nl