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Towards an Investigation of
Opportunities for Refactoring
to Design Patterns
Norihiro Yoshida, Katsuro Inoue
Osaka University
Department of Computer Science,
Graduate School of Information Science & Technology,
Osaka University
1
Refactoring

Refactoring is a technique for restructuring an
existing code[1].
 Alter
software’s internal structure without changing its
external behavior
 Improve the maintainability of software

We have worked on refactoring support for code
clone.
New method
Call statements
[1] M. Fowler, Refactoring: improving the design of existing code, Addison Wesley, 1999.
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
2
Refactoring to Design Patterns

Improve design quality of software that lack of
design patterns
 J.
Kerievsky, Refactoring to Patterns, Addison Wesley,
2004.

27 refactoring patterns

Refactoring opportunity
 Procedure for performing refactoring using design pattern
 J.
Rajesh et al., JIAD: A tool to infer design patterns in
refactoring, PPDP 2004.
 M. O. Cinneide et al., A Methodology for the Automated
Introduction of Design Patterns, ICSM 1999.
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
3
An Example of Refactoring to Design
Pattern

Introduce Polymorphic Creation with Factory Method
Condition 1
Before Refactoring
junit::framework::TestCase
DOMBuilderTest
XMLBuilderTest
testAddAboveRoot
testAddAboveRoot
Similar methods belong to classes that
have a common parent class.
Condition 2
・・・
builder = new DOMBuilder(…);
・・・
Only difference among similar methods
is an object creation step.
・・・
builder = new XMLBuilder(…);
・・・
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
4
An Example of Refactoring to Design
Pattern

Introduce Polymorphic Creation with Factory Method
Before Refactoring
After Refactoring
junit::framework::TestCase
junit::framework::TestCase
AbstractBuilderTest
#builder: OutputBuilder
DOMBuilderTest
XMLBuilderTest
testAddAboveRoot
It’s
easy to addtestAddAboveRoot
new test
class.
・・・
builder = new DOMBuilder(…);
・・・
・・・
builder = new XMLBuilder(…);
・・・
createBuilder
testAddAboveRoot
Factory Method:
Creator
・・・
builder = new
createBuilder(“orders”);
・・・
Factory Method:
ConcreteCreator
DOMBuilderTest
XMLBuilderTest
createBuilder
createBuilder
return new DOMBuilder(…);
return new XMLBuilder(…);
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
5
Our Research Question and Plan

Research Question
 What
kind of refactoring opportunities are
involved in software systems?

Research Plan
 Develop
an automated tool that identifies
opportunities
 Carry out the investigation using the tool
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
6
Automation of Identifying Opportunities

Introduce Polymorphic Creation with Factory Method
Condition 1
Before Refactoring
junit::framework::TestCase
Similar methods belong to classes that
have a common parent class.
Step 1
DOMBuilderTest
XMLBuilderTest
testAddAboveRoot
testAddAboveRoot
Detect similar methods using a code
clone detection tool such as CCFinder
Condition 2
・・・
builder = new DOMBuilder(…);
・・・
・・・
builder = new XMLBuilder(…);
・・・
Only difference among similar methods
is an object creation step.
Step 2
Evaluate whether detected methods
include object creation statements
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
7
Investigation points and Anticipated
Results

Investigation points
 How
many refactoring opportunities exist?
 Is it possible to improve maintainability by
performing refactoring to design patterns?

Anticipated Results
 Quality
differences among design patterns
 A number
of refactoring opportunities
 The degree of change in the maintainability
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
8
Summary and Current Status

We show a plan for investigating opportunities for
refactoring to design patterns.
 The
automated tool that identifies opportunities for
refactoring to design patterns
 Our investigation points and anticipated results

We are currently investigating ANTLR.
 ANTLR

2.7.4 (47,000 LOC, 285 Classes)
Open source compiler-compiler
 Our
tool detected 16 opportunities in ANTLR
Department of Computer Science, Graduate School of Information Science & Technology, Osaka University
9

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