1. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 1 Towards an Investigation of Opportunities for Refactoring to Design Patterns Norihiro Yoshida, Katsuro Inoue Osaka University

2. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 2 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.

3. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 3 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.

4. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 4 An Example of Refactoring to Design Pattern DOMBuilderTestXMLBuilderTest junit::framework::TestCase testAddAboveRoot ・・・ builder = new DOMBuilder(…); ・・・ builder = new XMLBuilder(…); ・・・ Introduce Polymorphic Creation with Factory Method Before Refactoring Condition 1 Similar methods belong to classes that have a common parent class. Condition 2 Only difference among similar methods is an object creation step.

5. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 5 An Example of Refactoring to Design Pattern Introduce Polymorphic Creation with Factory Method DOMBuilderTestXMLBuilderTest junit::framework::TestCase testAddAboveRoot ・・・ builder = new DOMBuilder(…); ・・・ builder = new XMLBuilder(…); ・・・ AbstractBuilderTest junit::framework::TestCase createBuilder #builder: OutputBuilder testAddAboveRoot ・・・ builder = new createBuilder(“orders”); ・・・ DOMBuilderTestXMLBuilderTest Factory Method: Creator Factory Method: ConcreteCreator return new DOMBuilder(…); return new XMLBuilder(…); createBuilder Before RefactoringAfter Refactoring It’s easy to add new test class.

6. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 6 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

7. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 7 Automation of Identifying Opportunities DOMBuilderTestXMLBuilderTest junit::framework::TestCase testAddAboveRoot ・・・ builder = new DOMBuilder(…); ・・・ builder = new XMLBuilder(…); ・・・ Introduce Polymorphic Creation with Factory Method Before Refactoring Condition 1 Similar methods belong to classes that have a common parent class. Condition 2 Only difference among similar methods is an object creation step. Step 1 Detect similar methods using a code clone detection tool such as CCFinder Step 2 Evaluate whether detected methods include object creation statements

8. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 8 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

9. Department of Computer Science, Graduate School of Information Science & Technology, Osaka University 9 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