Refactoring for Software Design Smells
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The document discusses the importance of applying design principles to create high-quality software, introducing key architectural and software design principles known as SOLID. It highlights the concept of 'code smells'—indicators of potential issues in code structure—and discusses tools for managing technical debt, such as SonarQube. The author emphasizes that understanding and addressing these design and architectural principles are essential for effective software refactoring and overall project success.
![Refactored Example …
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);
ZoneId id = ZoneId.of("Asia/Tokyo");
System.out.println(id);
LocalDateTime todayAndNow = LocalDateTime.now();
System.out.println(todayAndNow);
ZonedDateTime todayAndNowInTokyo = ZonedDateTime.now(ZoneId.of("Asia/Tokyo"));
System.out.println(todayAndNowInTokyo);
2016-03-17
13:28:06.927
Asia/Tokyo
2016-03-17T13:28:06.928
2016-03-17T16:58:06.929+09:00[Asia/Tokyo]](https://image.slidesharecdn.com/refactoringforsoftwaredesignsmells-160317173059/85/Refactoring-for-Software-Design-Smells-37-320.jpg)
Refactoring for Software Design Smells
- 1. Refactoring for Software Design Smells Ganesh Samarthyam ganesh.samarthyam@gmail.com
- 2. “Applying design principles is the key to creating high-quality software!” Architectural principles: Axis, symmetry, rhythm, datum, hierarchy, transformation
- 3. Who coined the term “code smell”?
- 4. Kent Beck
- 5. Who coined the acronym “SOLID”? (as in SOLID principles)
- 6. Michael Feathers S Single Responsibility Principle Every object should have a single responsibility and that should be encapsulated by the class O Open Closed Principle Software should be open for extension, but closed for modification L Liskov’s Substitution Principle Any subclass should always be usable instead of its parent class I Interface Segregation Principle Many client specific interfaces are better than one general purpose interface D Dependency Inversion Principle Abstractions should not depend upon details. Details should depend upon abstractions
- 7. Why Care About Design Quality? When, due to constraints, I design quickly and dirty, my project is loaded with technical debt
- 9. The City Metaphor Source: http://indiatransportportal.com/wp-content/uploads/2012/04/Traffic-congestion1.jpg
- 10. The 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.
- 11. Tool: CodeCity!
- 13. Smell Example logger.severe(“details”) errlog.log(“details”)logger.error(“details”) System.err.println(“details”) Since ROI (Return On Investment) is not clear, how to get management buy-in for this refactoring? Log4j java.util.logging custom log library SOPs
- 17. Code Smell Example class%GraphicsDevice% %public%void%setFullScreenWindow(Window%w)%{% %%%%%%%%if%(w%!=%null)%{% %%%%%%%%%%%%if%(w.getShape()%!=%null)%{%w.setShape(null);%}% %%%%%%%%%%%%if%(w.getOpacity()%<%1.0f)%{%w.setOpacity(1.0f);%}% %%%%%%%%%%%%if%(!w.isOpaque())%{% %%%%%%%%%%%%%%%%Color%bgColor%=%w.getBackground();% %%%%%%%%%%%%%%%%bgColor%=%new%Color(bgColor.getRed(),% % %% %bgColor.getGreen(), % %%%% %bgColor.getBlue(),%255);% %%%%%%%%%%%%%%%%w.setBackground(bgColor);% %%%%%%%%%%%%}% %%%%%%%%}% …% }% This%code%in% GraphicsDevice%uses% more%methods%of% Window%than%calling% its%own%methods!% “Feature envy” smell
- 18. Focus on Design Smells
- 19. Initial Journal Paper Published in Journal of Object Technology (Vol. 12, No. 2, 2013) S G Ganesh, Tushar Sharma, Girish Suryanarayana. Towards a Principle-based Classifica4on of Structural Design Smells. In Journal of Object Technology, vol. 12, no. 2, 2013, pages 1:1–29.doi:10.5381/jot.2013.12.2.a1 URL: hLp://www.jot.fm/issues/issue_2013_06/arPcle1.pdf (open access)
- 20. … and a Conference Paper
- 21. Finally a Book
- 22. For Architects: Design is the Key!
- 23. Why Care About Principles?
- 24. Equivalent Principles in Software Design? Architectural principles: Axis, symmetry, rhythm, datum, hierarchy, transformation
- 25. Equivalent Principles in Software Design! Principles* Abstrac/on* Encapsula/on* Modulariza/on* Hierarchy*
- 26. Proactive Application: Enabling Techniques
- 28. Design Smells: Example #1
- 30. Design Smells: Example #2
- 32. Design Smells: Example #3
- 33. Discussion Example // 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!
- 34. So What! Date today = new Date(); System.out.println(today); Date todayAgain = new Date(); System.out.println(todayAgain); System.out.println(today.compareTo(todayAgain) == 0); Thu Mar 17 13:21:55 IST 2016 Thu Mar 17 13:21:55 IST 2016 false What is going on here?
- 36. Refactored Solution LocalDate today = LocalDate.now(); System.out.println(today); LocalDate todayAgain = LocalDate.now(); System.out.println(todayAgain); System.out.println(today.compareTo(todayAgain) == 0); 2016-03-17 2016-03-17 true Works fine now!
- 37. Refactored Example … 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); ZoneId id = ZoneId.of("Asia/Tokyo"); System.out.println(id); LocalDateTime todayAndNow = LocalDateTime.now(); System.out.println(todayAndNow); ZonedDateTime todayAndNowInTokyo = ZonedDateTime.now(ZoneId.of("Asia/Tokyo")); System.out.println(todayAndNowInTokyo); 2016-03-17 13:28:06.927 Asia/Tokyo 2016-03-17T13:28:06.928 2016-03-17T16:58:06.929+09:00[Asia/Tokyo]
- 38. More classes in Date/Time API
- 40. Refactoring: Practical concerns “Fear of breaking working code” Is management buy-in necessary for refactoring? How to refactor code in legacy projects (no automated tests, difficulty in understanding, lack of motivation, …)? Where do I have time for refactoring?
- 41. “Applying design principles is the key to creating high-quality software!” Architectural principles: Axis, symmetry, rhythm, datum, hierarchy, transformation
- 42. email sgganesh@gmail.com website www.designsmells.com twitter @GSamarthyam linkedin bit.ly/sgganesh slideshare slideshare.net/sgganesh