Restructuring
Tudor Gîrba
www.tudorgirba.com

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cycle
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What?
{ { {
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} restructuring } }
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Restructuring is often taken
as a synonym of refactoring

Refactoring is a disciplined
technique for restructuring an
existing body of code, altering its
internal structure without
changing its external behavior

Refactoring is
behavior-preserving
transformation

Restructuring is transforming
a program to fit current needs

Why?
{ {
What?
{ { {
{
} { {
}
} restructuring } }
} { } } }

Software should be
habitable

The secret to tidiness is to have a
place for every thing
Denker
Markus

The secret to tidiness is to find the right
place for every thing
Denker
Markus

If it stinks, change it
Be ck
Gr andma

How?
Why?
{ {
What?
{ { {
{
} { {
}
} restructuring } }
} { } } }

Take a critical look at design

A God Class centralizes too much intelligence
Class uses directly more than a
few attributes of other classes
ATFD > FEW
Functional complexity of the
class is very high
AND GodClass
WMC ! VERY HIGH
Class cohesion is low
TCC < ONE THIRD
006
ari nescu 2
L anza, M

ModelFacade
from ArgoUML

p God Class
Split u
ModelFacade
from ArgoUML
2
er etal 200
Demey

d than done
Easi er sai
2
er etal 200
Demey

also w rap it
You can
2
er etal 200
Demey

you do not
Maybe uch it at all
need to to
God Class
in the last version
isGodClass(last)
AND Harmless God Class
Stable throughout
the history
Stability > 90%
4
Ratiu etal, 200

Client Provider
service()

Client Intermediary Provider
getProvider() service()

Client Intermediary Provider
getProvider() service()
this.intermediary.provider.service();

Provider2
service2()
Client Intermediary Provider
getProvider() service()
Provider3
service3()
this.intermediary.provider.service();
this.intermediary.provider2.service2();
this.intermediary.provider3.service3();

Provider2
service2()
Client Intermediary Provider
getProvider() service()
Provider3
service3()
this.intermediary.provider.service();
this.intermediary.provider2.service2();
this.intermediary.provider3.service3();
to str angers
eter : D on’t talk
of Dem
T he Law

Code
te Nav igation
E limina Provider2
service2()
Client Intermediary Provider
fullService() service()
Provider3
service3()
this.intermediary.fullService();
2
er etal 200
Demey

ge inte rfaces
ad to hu
t: This can le Provider2
Cavea service2()
Client Intermediary Provider
fullService() service()
Provider3
service3()
this.intermediary.fullService();
2
er etal 200
Demey

Middl e Man
R emove Provider2
service2()
Client Provider
service()
Provider3
service3()
this.provider.service();
this.provider2.service2();
this.provider3.service3();
Fow ler 1999

An Envious Method is more interested
in data from a handful of other classes
Method uses directly more than
a few attributes of other classes
ATFD > FEW
Method uses far more attributes
of other classes than its own
AND Feature Envy
LAA < ONE THIRD
The used \"foreign\" attributes
belong to very few other classes
FDP ! FEW
006
ari nescu 2
L anza, M

ser to Data
Behavi or Clo
Move

Data Classes are dumb data holders
Interface of class reveals data
rather than offering services
WOC < ONE THIRD
AND Data Class
Class reveals many attributes and is
not complex
006
ari nescu 2
L anza, M

ser to Data
Behavi or Clo
Move

Significant Duplication
006
ari nescu 2
L anza, M

A A
m1
m1'
m3
m2
m2'
6
ne scu 200
Lanza, Mari

A A
m3
B C B C
m1 m2 m1 m2
6
ne scu 200
Lanza, Mari

Restructuring can also improve performance

BusinessObject
Client BusinessSessionBean
BusinessEntityBean

BusinessObject
SessionFacade
Client BusinessSessionBean
BusinessEntityBean
java .sun.com

ModelFacade
from ArgoUML
es are good,
Not al l Facad od :)
some are G

Trouble never comes alone
Ano nymous

Redistribute Transform conditionals
responsibilities to Polymorphism
Eliminate Split up Transform Client ...
Navigation Code God Class Type Checks
Move Behavior Introduce Null Object
Closer to Data

es pro blems
ode co rrelat
inC

When?
How?
Why?
{ {
What?
{ { {
{
} { {
}
} restructuring } }
} { } } }

Restructure all the time

Restructure all the time
his fea sible?
… hm m, is t

It is feasible

Development Maintenance

are evolution
Softw

Tudor Gîrba
www.tudorgirba.com
creativecommons.org/licenses/by/3.0/