My presentation at the dutch Spring meetup that was held at TU Delft on March, 2017.

1. Code smells in MVC systems
Maurício Aniche
@mauricioaniche

2. beautiful code

3. I will find a solution for that!

4. Of course I didn’t…

5. What’s the ugliest thing
you see in a source code?

6. Long methods
Complex methods
God classes
Coupled classes
Non cohesive
classes

7. The dark side I sense in
you…
I feel these ones
are not enough!

8. 8
Talk to developers you
should, young
padawan!

9. Why?
their own smells each part
of the architecture has!

10. A catalogue
of smells
specific to MVC
(after talking to 20+70 developers)
10
Grrrrrr…
Controllers that offer many
services
Grrrr…
Repositories that deal with
many Entities
Grrrrr…
Aniche, Maurício, Bavota, Gabriele, Treude, Christoph, van Deursen, Arie, Gerosa, Marco.“A Validated Set of Smells in
Model-View-Controller Architecture”. Software Maintenance and Evolution (ICSME), 2016, 32th International

11. Promiscuous Controller
Offers too many actions
ICSME 2016 11

12. Brain
Controller
Too much business logic
ICSME 2016 12

13. Meddling Service
Queries the database
ICSME 2016 13

14. Brain Repository
Complex logic (SQL or code)
ICSME 2016 14

15. Laborious Repository
Method
Many queries in a single method
ICSME 2016 15

16. Fat Repository
Manages many entities
ICSME 2016 16

17. Spring MVC in github
ICSME 2016 17

18. Detection strategies
ICSME 2016 18
3Q + 1.5IRQ

19. Smelly classes exist!
ICSME 2016 19

20. Are they smells?
ICSME 2016 20

21. Developers’ perceptions
Significantly different
ICSME 2016 21

22. OOP attributes?
Think about context you
should!We wanna
measure OO
attributes, but
we don’t agree
with the results!

23. 23
Sugar level 150 [70,120]

24. 24
Coupling 10 < 15
How to find
this number?

25. SCAM 2016 25
Benchmarking

26. Benchmark
in Controllers
26

27. Benchmark
in Controllers
27

28. That’s not what
we want
28

29. 29
Quantiles
Coupling(CBO)
Aniche, M., Treude, C., Zaidman, A., van Deursen, A., Gerosa, M.A., “SATT: Tailoring Code Metric Thresholds for Different Software
Architectures”. 16th IEEE International Working Conference on Source Code Analysis and Manipulation, 2016.

30. 30
Experts
explained to us

31. SATT for the rescue
31

32. 32

33. It indeed became a tool!
33

34. Database-centric code
Because in the wrong
place, they are!It’s very hard to
find some SQL
queries in my
codebase…

35. Queries can get complicated!
SELECT
p.name as project,
c.id as commitId,
a.name as artifactName,
a.path as artifactPath
FROM
Projects p
JOIN
Commits c ON c.project_id = p.id
JOIN
Artifacts a ON a.commit_id = c.id
WHERE
p.repository = ’Apache’;
Where
should I put
it?

36. Project # of
classes
# of
commits
# of DAOs # of
methods
Gnarus 924 10451 39 233
Caelumweb 1321 12077 81 590
There are many queries!

37. public class InvoiceDAO {
public Invoice findById(int id) { … }
public ShoppingCart find(User u) { … })
public List<Invoice> getAll() { … }
public void save(Invoice inv) { ...}
}
By the method
signatures we
should!
Where should
we start?

38. Project # of DAO
methods
# of
”correct”
methods
# of
”wrong”
methods
% of
wrong
methods
Caelumweb 590 511 79 13.38%
Gnarus 233 200 33 14.16%
Project # of
inspected
methods
# of
agreement
% of
agreement
Caelumweb 79 59 74.68%
Gnarus 33 16 48.48%
Aniche, Maurício F., Gustavo A. Oliva, and Marco A. Gerosa. “Are the Methods in Your Data Access Objects (DAOs) in the Right Place?
A Preliminary Study.”. 6th Workshop on Managing Technical Debt, in conjunction with ICSME2014, Canada. Short paper.

40. Test code stability
Not happen it should!
We hate system
testing because
we have to
rewrite them
often!

41. Large selenium code is!

42. Change frequently, web
applications

43. A catalogue
of patterns
43
Fixture API
ID in HTML
Move Fast, Move Slow
…
Aniche, M., Guerra, E., Gerosa, M. “A Set of Patterns to Improve Code Quality of Automated Functional Tests of Web
Applications”. 21th Conference on Pattern Languages of Programs. 2014.

44. A lot of storytelling…
(from the beginning!)

45. We do need hard evidence of the importance
of code smells… but how?

46. The solution?
How to measure
readability, ease to
maintain, ease to
test, ease for
someone else to
start to maintain,
etc, how much it
slows me down?
Answers I don’t have…

47. 47
I’ll find out! 

49. Thanks!
@mauricioaniche
Young me working on a low
quality code that I wrote myself at
my first international project
(Dominican Republic, 2006).
Sorry about my hair.
My bosses doing peer press… oops,
pair programming!