Many useful software products are started with tightly coupled “spaghetti” code that just works. As lines of code and complexity increase, teams often struggle to make modifications and add new features without impacting the entire application. As a result, previously successful applications start missing dates and suffering from degrading quality. OSGi can help by introducing a modular design that decouples the architecture, separates concerns, and manages dependencies. Unfortunately it often takes a few missed dates before a team realizes how important modularity is. Don’t let your existing product become a victim of its own success. Learn how to introduce modularity to existing software projects using Apache Felix. Discover how your application can evolve into a pluggable standards driven framework. It’s never too late to reap the benefits of modularity!

1. Adding Modularity Afterward with
Embedded OSGi
Adding Modularity Afterward with
Embedded OSGi

2. About Me – Bob Paulin
• @bobpaulin/bob@bobpaulin.com/http://bobpaulin.com
●
Independent Consultant
• Web Centric Platforms
• Business Enablement
• Continuous Delivery
Chicago Java Users Group (CJUG) Community Leader
• Need a Mentor? mentors@cjug.org
• Want to Present in Chicago? present@cjug.org
Proud Father/Husband with 3 kids (and a Cat since Developers all seemed
to like cats)

3. Regret

4. Application Development Cycle

5. Hope?

6. If we could start over what
would we want?

7. Modularity

8. Options?

9. OSGi
● Mature 10+ Years
● Tools
● Modularity is enforced
● Versioning
● Complex Classloading
● Runtime
● Mature 10+ Years
● Tools
● Modularity is enforced
● Versioning
● Complex Classloading
● Runtime

10. Inversion of Control (IoC)
● Lightweight
● Easily added to existing systems
● Tools
● Modularity not enforced (DIY)
● No Versioning
● Lightweight
● Easily added to existing systems
● Tools
● Modularity not enforced (DIY)
● No Versioning

11. Jigsaw
● Java 7....8...9??
● Versioning
● Interoperability with OSGi (Penrose)
● Java 7....8...9??
● Versioning
● Interoperability with OSGi (Penrose)

12. OSGi: Start with One
big Bundle?

13. OSGi: When does
embedding make sense?

14. Want an Isolated
Third-Party
Container

15. Working with
OSGi unfriendly
Libraries.

16. Licensing/Proprietary
Code

17. No
Budget/Time/Desire
for full OSGi

18. Embedded Design/Implementation

19. Exposing packages to the
framework via System Packages

20. Minimum required bundles
● Felix Framework● Felix Framework

21. A few more to consider...
● Felix Config Admin
● Gogo Shell
● Web Console + HTTP
● SCR + Annotations
● Apache ACE Management Agent
● Felix Config Admin
● Gogo Shell
● Web Console + HTTP
● SCR + Annotations
● Apache ACE Management Agent
A few more to consider...

22. ● Configuration
● Factories
● Resources
● Configuration
● Factories
● Resources
Good places to start

23. ● Framework creates threads
● Use only one Framework Instance
● Requires some IDE tricks
● Package Tangling may get worse before it
gets better (Use Sonar)
● Framework creates threads
● Use only one Framework Instance
● Requires some IDE tricks
● Package Tangling may get worse before it
gets better (Use Sonar)
Caveats

24. Talk is Cheap.
Time for an example.

25. ● SOAR 2D Grid Game
● Written in C++ with Java Bindings
● Code is Coupled
● SWT
● Multiple Games
● SOAR 2D Grid Game
● Written in C++ with Java Bindings
● Code is Coupled
● SWT
● Multiple Games
An Embedded Usecase With
Tanks

26. Embedded Design/Implementation

27. Exposing packages to the
framework via System Packages
configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
"edu.umich.soar,edu.umich.soar.gridmap2d.config," +
"edu.umich.soar.gridmap2d,edu.umich.soar.gridmap2d.world," +
"edu.umich.soar.gridmap2d.visuals," +
"org.eclipse.swt.widgets,org.eclipse.swt.graphics; version=0.0.1");

28. Setting up the Framework
//Yup it's that easy!
m_felix = new Felix(configMap);
m_felix.start();

29. Supplying Services to the Non-
OSGi code
public <S> S getService(Class<S> serviceClass)
{
ServiceReference<S> ref = m_activator.getContext()
.getServiceReference(serviceClass);
return m_activator.getContext().getService(ref);
}

30. Supplying more than one
public <S> List<S> getServices(Class<S> serviceClass, String filter)
{
Collection<ServiceReference<S>> refCollection = null;
try {
refCollection = hostActivator.getContext().getServiceReferences(serviceClass, filter);
} catch (InvalidSyntaxException e) {
LOGGER.error("Invalid Syntax", e);
}
List<S> result = new ArrayList<S>();
if(refCollection == null)
{
throw new ModuleException("No services References Could be found for the given class");
}
for(ServiceReference<S> currentRef : refCollection)
{
result.add(hostActivator.getContext().getService(currentRef));
}
return result;
}

31. DEMO!

32. Summary
● Modularity is often an afterthought
● Some projects have difficulty being fully
OSGi
● Embedding OSGi can provide many of the
same benefits
● Modularity is often an afterthought
● Some projects have difficulty being fully
OSGi
● Embedding OSGi can provide many of the
same benefits

33. References
● Adding Modularity Afterwards with Embedded OSGi (Talk and Code)
● Felix Embedded Documentation
● Adding Modularity Afterwards with Embedded OSGi (Talk and Code)
● Felix Embedded Documentation

34. Bob Paulin
@bobpaulin/bob@bobpaulin.com/http://bobpaulin.com