This document discusses using Tracer Bullet Development (TBD) and OSGi to develop software in an agile manner. TBD involves proposing system objects, interfaces, connecting interfaces, adding functions, and refining iteratively. A case study is presented of a speaker rental reservation system developed using TBD and OSGi. The system objects are defined along with interfaces for business services, data access, outbound messaging and inbound messaging. Functions are then added by coding implementations available on GitHub. The system is well-positioned for future refinement using TBD principles.

1. Agile Development with OSGi
Matt Stine

2. About your speaker...
IT Manager / Business Analyst / Software
Architect by Day
Speaker (JavaOne, SpringOne/2GX, Lambda
Lounge, NFJS, RWX, PAX)
Author (GroovyMag, NFJS the Magazine)
President of the Memphis/Mid-South Java User
Group
Agile Zone Leader @ DZone
OSGi Enthusiast

3. A Tale of Two Cities:
Tracer Bullet Development
OSGi

4. Where it all began...

5. ...OK, really
this time!

6. A rose by any other name...
Walking Skeleton (Alistair Cockburn)
http://alistair.cockburn.us/Walking+skeleton
Spanning Application/Matrix (Mary & Tom Poppendieck)
Lean Software Development: An Agile Toolkit
Nested Synchronization (Mary & Tom Poppendieck)
Implementing Lean Software Development
Hudson River Company Start (Johanna Rothman)
Manage It!
Thread (Matt Simons)
“Big and Agile?” Cutter IT Journal 15(1): January 2002.
Spike (Luke Hohmann)
Beyond Software Architecture: Creating and Sustaining Winning Solutions

7. Propose
System
Objects
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

8. Propose System Objects
Identify application layers/modules
e.g. Client, Server, Database
Must be able to stand alone
Keep as coarse grained as possible
Must be able to justify isolated developer/team

9. Propose
System
Objects
Propose
Interfaces
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

10. Propose Interfaces
Define contract between system objects
Collaborative effort
Agree on method names, signatures
Stub out implementations (canned data)
Define how layers will talk (e.g. direct API calls, RMI,
SOAP, OSGi, JMS)
System architecture “emerges”

11. Propose
System
Objects
Propose
Interfaces
Connect
Interfaces
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

12. Connect Interfaces
Implement interobject communication
Many issues will emerge - resolve them!
Now the tracer bullet can be fired!

13. Propose
System
Objects
Propose
Interfaces
Connect
Interfaces
Add
Functions
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

14. Add Functions
Finally time to add real production code!
Developers/teams can work in isolation now
Work from high priority/high risk to low priority/low risk
Start to address performance problems

15. Propose
System
Objects
Propose
Interfaces
Connect
Interfaces
Add
Functions
Refactor,
Refine,
Repeat
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

16. Refactor, Refine, Repeat
Interfaces will evolve
Add/change at any time, but...
No broken windows!!!
Within module, refactor mercilessly!
Between modules, must communicate!

17. Propose
System
Objects
Propose
Interfaces
Connect
Interfaces
Add
Functions
Refactor,
Refine,
Repeat
Tracer
Bullet
Development
Inspired by Ship It! (Richardson/Gwaltney), page 127

18. TBD Benefits
Teams can work in parallel, independently
Can demonstrate “working” system earlier, providing feedback to you
sooner
New features can be demonstrated immediately
Loosely coupled, highly cohesive modules
Encapsulation of module details
Enables automated integration testing
Enables interteam communication
Enables staff reallocation

19. OSGi
The Dynamic Module system for Java

20. OSGi Architecture
Hardware
Operating System
Java Virtual Machine
Modules
Lifecycle
Service Registry
Services
Security
Application/Bundles
OSGiPlatformJavaPlatform
Inspired by Modular Java (Craig Walls), page 16

21. SOA in a JVM!
Service
Bundle
Consumer
Bundle
RegistersService
DiscoversService
Consumes Service
Inspired by Modular Java (Craig Walls), page 17
OSGi
Service
Registry

22. Modularity...how?
Encapsulation
Service Registry
Versioning

23. Bundle Versioning
Bar
1.0.2
Zab
2.1.3
Inspired by Modular Java (Craig Walls), page 18
Foo
1.0.0
Zab
1.0.4
Qib
2.0.1

24. Modularity...how?
Encapsulation
Service Registry
Versioning
Dynamism/Lifecycle

25. OSGi Implementations
Equinox

26. PAX Tools for OSGi

27. PaxConstruct
Script-oriented toolkit for OSGi development
Similar to Rails/Grails development model
Built on Maven 2

28. PaxRunner
OSGi framework launcher
Facilitates quick start OSGi exploration
Facilitates swapping OSGi platforms (works with all
major open source implementations)
Facilitates provisioning OSGi bundles from multiple
sources
Magic behind “pax-provision” and PaxExam

29. PaxExam
Testing toolkit for OSGi
Facilitates in-container integration testing of bundles
Flow:
Starts OSGi container of choice
Provisions and starts selected bundles
Injects OSGi BundleContext to your JUnit test
Executes a test method
Rinse and repeat until done!

30. Why TBD+OSGi?
Connect
Interfaces

31. Why TBD+OSGi?
Connect
Interfaces
Client
Object
Client Module
Service
Interface
Service
Implementation
Server Module

32. Case Study

33. As a customer I can browse for speakers and select
one so that I can reserve him/her.
As a customer I can reserve my chosen speakers at
any Fluffbox location at which he/she is available so
that I can pick him/her up.
As a kiosk, I can notify the reservation system when
speakers are picked up/returned so that customers will
have an up-to-date view of what speakers are
available.
Online Reservation System for Speaker Rental Kiosks

34. System Objects
Web UI
Business Services
Data Access
Outbound
Messaging
Database Kiosk
Inbound
Messaging

35. Business Services Interface
List<Speaker> browse();!
!
Speaker get(Long id);!
!
List<Kiosk> findKiosksWhereAvailable(Speaker speaker);!
!
Kiosk get(Long id);!
!
Rental reserve(Speaker speaker, Kiosk kiosk, Customer
customer);!
!
void pickup(Rental rental);!
!
void returnRental(Rental rental, Kiosk kiosk);!

36. Data Access Interface
List<Speaker> findAll();!
!
Speaker get(Long id);!
!
List<Kiosk> findKiosksWhereAvailable(Speaker speaker);!
!
Kiosk get(Long id);!
!
Rental create(Rental rental);!
!
void pickup(Rental rental);!
!
void returnRental(Rental rental);!

37. Outbound Messaging
Interface
void notifyKioskOfRental(Kiosk kiosk, Rental rental);

38. Inbound Messaging
Interface
void notifyHqOfRentalPickup(Rental rental);!
!
void notifyHqOfRentalReturn(Rental rental, Kiosk kiosk);

39. Connect Interfaces
Web UI
Business Services
Data Access
Outbound
Messaging
Database Kiosk
Spring DM/OSGi
OSGi
JDBC
Spring DM/OSGi
JMS JMS
Spring DM/OSGi
Inbound
Messaging

40. Add Functions
On to the code...
Code available at:
http://github.com/
mstine/fluffbox

41. Refactor, Refine, Repeat
Maybe change out plain JMS for Spring Integration
solution
Maybe track spatial data on locations to enable
mapping
Still need to add a payment system - another system
object?
Our TBD system puts us in great position to address
any of these and more!

42. Please fill out your evaluations!
Matt Stine
matt.stine@gmail.com
Twitter: mstine
http://www.mattstine.com