In the last two decades, refactoring for code and design smells have received considerable attention from both academia and industry. Recently, the focus has turned towards refactoring for architectural smells to repay architectural debt. This presentation covers case studies/examples in refactoring them in industrial and open source projects.

1. Architecture Refactoring
Accelerating Business Success
Ganesh Samarthyam, Corporate Trainer and Author
www.designsmells.com

2. Architecture is all about
realising business needs
Abstract business
need (requirements)
Concrete implementation
(code)
Architecture
& Design

3. … but business needs keep
changing!

4. …with that we need to adapt
the software

5. City metaphor
“Cities grow, cities evolve, cities
have parts that simply die while other
parts flourish; each city has to be
renewed in order to meet the needs of its
populace… Software-intensive systems
are like that. They grow, they evolve,
sometimes they wither away, and
sometimes they flourish…”
Grady Booch in the foreword for “Refactoring for Software Design Smells: Managing Technical Debt”, Girish Suryanarayana, Ganesh Samarthyam, Tushar Sharma, Morgan Kaufmann/Elsevier, 2014.

6. What is architecture debt?
…
Architecture)
debt)
Architecture)
smells)
Architecture)
viola2ons)
Design)debt)
Design)smells)
Viola2ons)of)
design)rules)
Test)debt)
Lack)of)tests)
Inadequate)test)
coverage)
Code)debt)
Sta2c)analysis)
tool)viola2ons)
Inconsistent)
coding)style)

7. Key reasons for architecture
refactoring
Address new
business
needs
Increase
feature
velocity
Address
architecture
decay
Realizing
NFRs
Modernize
Reduce costs

8. Code refactoring
margin = c.getMargin();
if (c instanceof AbstractButton) {
margin = ((AbstractButton)c).getMargin();
} else if (c instanceof JToolBar) {
margin = ((JToolBar)c).getMargin();
} else if (c instanceof JTextComponent) {
margin = ((JTextComponent)c).getMargin();
}

9. Example: Refactoring for
design smells

10. Earlier (relatively) mature
work

11. Natural extension: Refactoring
for architectural smells
The$red$lines$in$this$
dependency$diagram$shows$
circular$dependencies$

12. Code refactoring Architecture refactoring
A module-level or class-level concern
A system level concern that cuts across
modules or sub-systems
Impact of refactoring is within a team Impact of refactoring is often across teams
Typically performed to improve the internal
structure of the code
Performed for various reasons: cost,
regulatory, security, performance, availability,
…
Management buy-in typically not required Management buy-in is typically required
Upfront planning is typically (relatively)
limited
Upfront planning and co-ordination
(sometimes between teams) is often required
Unit tests are important to ensure that
“behaviour is preserved”
Unit tests, integration tests, system tests,
NFR tests, … are required
Risk of breaking the working software is
relatively low
Risk of breaking the working software is
relatively high
Real-world analogy:
“fixing potholes”
Real-world analogy:
“metro construction”

13. COTS
(Commercial Off The Shelf)
FOSS
(Free and Open Source Software)
Make
Buy
/ Reuse
Proven
technologies
Cutting-edge
technologies
Architecting: the process of
taking design decisions!

14. Cross-cutting concerns
Error/Exception handling
ConcurrencyPersistence
Event handling
Interaction and presentation
Source: SWEBOK v3

15. Case study: Using
Structured EH
Source: https://msdn.microsoft.com/en-us/library/windows/desktop/ms681409(v=vs.85).aspx
Structured Exception
Handling in VC++
Standard Exception
Handling supported in
modern C++ compilers
bool SafeDiv(Number dividend, Number divisor,
Number &result) {
try {
result = dividend / divisor;
} catch(Number::divide_by_zero ex) {
return false;
}
return true;
}
BOOL SafeDiv(Number dividend, Number divisor,
Number &result) {
__try {
result = dividend / divisor;
} __catch(GetExceptionCode() == EXCEPTION_INT_DIVIDE_BY_ZERO
? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) {
return FALSE;
}
return TRUE;
}

16. Handling persistence
Oracle DB
Compo
nent-1
Compo
nent-2
Compo
nent-N
[establish
connection, SQL
queries, close
connection…]
No clone within a
component, but
duplication of code
across components
How to support
different databases?
[establish
connection, SQL
queries, close
connection…]
[establish
connection, SQL
queries, close
connection…]

17. Handling persistence
Compo
nent-1
Compo
nent-2
Compo
nent-N
Service layer /
DAL

18. Case Study #1:
Refactoring Windows

19. Refactoring Windows

20. Refactoring Windows
“A large number of dependencies at the module level
could be reduced and optimized to:
* make modular reasoning of the system more efficient
* maximize parallel development efficiency
* avoid unwanted parallel change interference
* selectively rebuild and retest subsystems effectively”
Refactoring performed to reduce
and optimize dependencies - by
creating and enforcing layering
Source: Kim, Miryung, Thomas Zimmermann, and Nachiappan Nagappan. "An Empirical Study of RefactoringChallenges and Benefits at Microsoft."
IEEE Transactions on Software Engineering 7 (2014): 1-1.

21. Refactoring Windows:
Significant Characteristics
Refactoring decisions made after substantial
analysis of existing dependency structure
Refactoring effort was centralized and top
down with designated team for refactoring
Use of custom refactoring tools (MaX)
and processes (quality gate check)
Source: Kim, Miryung, Thomas Zimmermann, and Nachiappan Nagappan. "An Empirical Study of RefactoringChallenges and Benefits at Microsoft."
IEEE Transactions on Software Engineering 7 (2014): 1-1.

22. Refactoring Windows
Source: Kim, Miryung, Thomas Zimmermann, and Nachiappan Nagappan. "An Empirical Study of RefactoringChallenges and Benefits at Microsoft."
IEEE Transactions on Software Engineering 7 (2014): 1-1.

23. Case Study #2:
Refactoring Date & Time
support in JDK

24. Poor API design in JDK for
date/time
e.g., in java.util.Date
class, days start at 0,
months start at 1, years start
at 1900!
Prior to Java 8, API design for date and
time in JDK was poor

25. Date/Time related woes
// using java.util.Date
Date today = new Date();
System.out.println(today);
$ java DateUse
Wed Dec 02 17:17:08 IST 2015
Why should we get the
time and timezone details
if I only want a date? Can
I get rid of these parts?
No!

26. Example of a design smell in
Date class
“Refused
bequest” smell

27. Joda API & JSR 310
JSR 310: Java Date and Time API
Stephen Colebourne

28. LocalDate in java.time
package
// using java.time.LocalDate
LocalDate today = LocalDate.now();
System.out.println(today);
$ java DateUse
2015-12-02
I can use (and hence
depend upon) only date
related functionality (not
time, zone, etc)

29. LocalDate in java.time
package
You can use only date,
time, or even timezone,
and combine them as
needed!
LocalDate today = LocalDate.now();
System.out.println(today);
LocalTime now = LocalTime.now();
System.out.println(now);
LocalDateTime todayAndNow = LocalDateTime.now();
System.out.println(todayAndNow);
ZonedDateTime todayAndNowInTokyo = ZonedDateTime.now(ZoneId.of("Asia/Tokyo"));
System.out.println(todayAndNowInTokyo);
2015-12-02
17:37:22.647
2015-12-02T17:37:22.648
2015-12-02T21:07:22.649+09:00[Asia/Tokyo]

30. Many useful classes in
java.time

31. Case Study #3:
Refactoring JDK!

32. Tangles in
JDK

33. Copyright © 2015, Oracle and/or its affiliates. All rights reserved

34. Copyright © 2015, Oracle and/or its affiliates. All rights reserved

35. Copyright © 2015, Oracle and/or its affiliates. All rights reserved

36. Project Jigsaw in Java 9
Modularize JDK & JRE
Hide platform internal details such as sun.misc
Provide a module system for Java developers

37. Case Study #4: Linux
Kernel

38. Linux: Intended Architecture

39. Linux: Extracted Architecture

40. Key challenges in
architecture refactoring
Getting
management
buy-in
Fear of breaking
working software
Lack of tool
support
Merge process
problems

41. Using tools for architecture
refactoring

45. Key take-aways
Architecture refactoring plays a key role in enabling business success
Architecture smells and violations contribute to technical debt (known
as architecture debt)
Code refactoring and architecture refactoring are altogether different
ballgames
We can learn from rich experience available on architecture
refactoring
Refactoring for architecture smells is an effective way to learn
software architecture!

46. “Architecture refactoring
accelerates business success”

47. Image credits
• http://sustainablecitiescollective.com/pratik-dave/244831/bangalore-exclusive-metro-india-having-profit-making-public-
transport-system
• http://www.medsoftwaresys.com/mss/wp-content/uploads/2012/04/reengineering.png
• http://topnews.in/files/Bangalore-Metro-Rail-Corporation-Ltd.jpg
• https://www.itdp.org/wp-content/uploads/2014/07/Chennai-Rendering.jpg
• http://www.vectors4all.net/preview/database-clip-art.jpg
• http://static.planetminecraft.com/files/resource_media/screenshot/1231/Windows-Vs-Mac_3072108.jpg
• http://manuel.midoriparadise.com/public_html/icons/linux-icon.png
• http://mortalpowers.com/posse/1280x1280/0DSC03205.JPG
• http://images.clipartpanda.com/server-computer-clipart-1216179635943364667jcartier_central_computer_1.svg.hi.png
• http://images.clipartpanda.com/cloud-icon-png-clouds.png
• http://www.clipartbest.com/cliparts/dc6/M5L/dc6M5LBc9.jpeg
• http://cdn.ttgtmedia.com/rms/computerweekly/refactor.jpg
• http://yellowairplane.com/Adventures/Falkland_Islands_War_Guestbook/Falkands_War_Malvinas_War_Photos/
Jet_Fighter_Mirage_2000_Takeoff_Argentina.jpg

48. www.designsmells.com bit.ly/sgganesh @GSamarthyam