This document discusses code quality in MVC systems and strategies for improvement. It describes analyzing 60k-110k lines of Java code to measure metrics like coupling and benchmarking controllers. The document outlines a catalogue of specific smells in MVC architectures and validated research on improperly placed database queries and data access object methods. It proposes moving queries to the correct place and improving test code stability with patterns to reduce rewriting.

1. Code quality in
MVC systems
Maurício Aniche
@mauricioaniche

3. 60k and 110k lines of
Java code!

4. Me beautiful code

5. 5
Sugar level 150 [70,120]

6. 6
Coupling 10 < 15
How to find
this number?

7. 7
Benchmarking

8. Benchmark
in Controllers
8

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

10. 10
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.

11. 11
Experts
explained to us

12. SATT for the rescue
12

13. 13

14. 14
Talk to developers you
should, young
padawan!

15. A catalogue
of smells
specific to MVC
(after talking to 50 developers)
15
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 Conference, IEEE, 2016.

16. 16
They are indeed
bad…
(prone to
change and to defects)

17. It indeed became a tool!
17

18. Bettercodehub like it! J

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

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

21. 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?

22. 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?

23. 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.

24. Phil Calçado just
(re-)blogged
about it!
http://philcalcado.com/2010/12/23/how_to_write_a_repository.html

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

26. Large selenium code is!

27. A catalogue
of patterns
27
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.

29. 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!