1. CS5103 Software Engineering Lecture 13 Software Refactoring Software Licenses

2. 2 Last class  Issue tracking system  Type of issues  Process of issues  Resolution of issues  Coding styles  Code  Variables and constants  Expressions  Statements and Lines  Blocks  Methods and Classes

3. 3 Today’s class  API comments and Documentation  Javadoc  Software refactoring  Why software refactoring?  Types of refactoring  Tool supports  Behind refactoring tools  Software license  Proprietary licenses  Open source software licenses

4. 4 Coding styles  Variable/Constant  Meaningful name, follow conventions, externalize constants  Expression  Break complex ones, avoid corner cases, more brackets  Statements/line  One statement per line, break long lines  Blocks  Logic blocks, Space indent, Curly brace for singletons, No copy-paste  Methods / Classes  Break to pieces when too large, smaller method signatures, follow common structures

5. 5 JavaDoc  A JavaDoc Example  Ant 1.6.5  http://api.dpml.net/ant/1.6.5/overview-summary.html http://api.dpml.net/ant/1.6.5/overview-summary.html

6. 6 JavaDoc  Structure  Overview  Packages  Classes / Interfaces / Exceptions  Fields / Constructors / Methods  Hierarchy  Deprecated  Index

7. 7 JavaDoc-Tags  Tags are meta-data put in the comments to guide Javadoc in document generation  Starting with “@”  @author : author of the class  @version: current version of the software  @since: the software version when the class is added  @see: a link to another class / method / …  @param: parameters of a method  @return: return value of a method  @exception: exceptions thrown from a method  @deprecated: an outdated method

8. 8 Javadoc: Mapping  Commenting methods for documentation /** * Constructs a WordTree node, specify its * data with the parameter word, both children * of the WordTree node are null * * @param word the string value stored as the data of the node, cannot be null * @exception NullWordException an exception raised when the parameter word is null */ public WordTree(String word) throws NullWordException{... /** * fetch the data of current WordTree node * @return the data stored at current node */ public String getData()...

9. 9 Javadoc: Mapping  Javadoc generated

10. 10 JavaDoc  Demo for generating Javadoc in eclipse  Right click on your project  Goto Export…, and choose Javadoc  You will need a Java SDK (not only JRE) to run Javadoc  Set the Javadoc command to the Javadoc executable  Set the destination to the place  Click on finish

11. 11 Today’s class  API comments and Documentation  Javadoc  Software refactoring  Why software refactoring?  Types of refactoring  Tool supports  Behind refactoring tools  Software license  Proprietary licenses  Open source software licenses

12. 12 Software Refactoring, why?  So far we talked about issues to be considered when design and implementing software  Design patterns  Coding Styles  Considering these, you can try to find a best implementation for the current requirements  But requirements change quickly…

13. 13 Software Refactoring  Definition:  Software refactoring the process of restructuring a software to improve its readability or extensibility, while keeping its behavior  Restructuring  Keeping its behavior  book  Refactoring- Improving the Design of Existing Code, Addison Wesley, 1999. Martin Fowler et al.

14. 14 When to apply refactorings  Bad smells  Code duplication  Long method / Huge Class  Long parameter list  ….  As the software evolve, these smells automatically appears  Especially when you do extreme programming, which tries to ignore design issues at the beginning

15. 15 Refactoring for design patterns  Consider the design patterns we learned  Composite Pattern  At the beginning, maybe simple document hierarchy (doc, line, glyph), no plan for changing the hierarchy  So fine without composite pattern  Factory Pattern  Support only one style at beginning  So fine without factory pattern  Visitor Pattern  Support only spell checking at beginning  So no need to bother for visitor patterns

16. 16 Types of refactorings  Add/Remove methods / fields  Move methods / fields  Extract methods / interface  Rename  Replace temp with query  Pull up / Push down methods / fields  …

17. 17 An example from Martin Fowler’s book  A program to calculate the bill of a video-store customer  The total amount depends on the movie renting prices, the number of movies rented and the renting dates  Class diagram

18. Example: Movie class public class Movie { private String title; private int priceCode; public Movie(String title, int priceCode) { this.title=title; this.priceCode = priceCode; } public String getTitle() { return this.title; } public int getPriceCode() { return this.priceCode; } public void setPriceCode(int priceCode) { this.priceCode = priceCode; }

19. Example: Rental class Rental public class Rental { private Movie movie; private int rentDay; public Rental(Movie movie, int rentDay) { this.movie = movie; this.rentDay = rentDay; } public int getDaysRented() { return Util.getCurrentDay() – this.rentDay ; } public Movie getMovie() { return this.movie; }

20. Example: Customer class Customer public class Customer { private String name; private List rentals =new ArrayList (); public Customer(String name) { this.name = name; } public void addRental(Rental rental) { this.rentals.addElement(rental); } public String getName() { return this.name; }

21. Example: Customer class(2) Customer public class Customer... public String statement() { double totalAmount = 0; String result = “ Rental Record for “ + getName() + “ \n ” ; for (Rental each : this.rentals) { double thisAmount = 0; // determine amounts for each line thisAmount = each.getMovie.getPriceCode() * each.getDaysRented(); totalAmount = totalAmount + thisAmount; result = result + each.getMovie.getName() + “ ” + each.getDaysRented() + “ ” + thisAmount + “ \n ” ; } // add footer lines result += “Amount owed is “+ totalAmount + “\n”; return result; }

22. 22 Here comes the change  Add discount code for movies  Old – 80% price  Regular – 90% price  Popular – 100% price  Add a html statement for sending online bills

23. 23 What to do?  Add conditional statements… for (Rental each : this.rentals) { double thisAmount = 0; // determine amounts for each line double discount = 1.0 if(each.getMovie().getDiscountCode() == DISCOUNT_OLD){ discount = 0.8; }else if(each.getMovie().getDiscountCode() == DISCOUNT_REG){ discount = 0.9 } thisAmount = each.getMovie().getPriceCode() * each.getDaysRented() * discount; totalAmount = totalAmount + thisAmount; result = result + each.getMovie.getName() + “ ” + each.getDaysRented() + “ ” + thisAmount + “\n”; }

24. 24 What to do?  Copy and paste statement() and revise it to generate a htmlStatement() method  The code looks much worse now compared with the start point  Long statement method  Duplicate code

25. 25 So after adding the two features, you plan to do refactoring  The main reason of the ugly code is ?  Statement() method is doing too many things (which are actually not parts of printing a statement)  Split it to three  Calculation of the amount on each line  Calculation of the amount sum  Print lines

26. 26 Refactoring 1  1a: Extract method to getItemAmount()  It is actually something related to a rental  So 1b: Move it to rental, to reduce duty of Customer  1c: Rename it to getAmount() double discount = 1.0 if(each.getMovie().getDiscountCode() == DISCOUNT_OLD){ discount = 0.8; }else if(each.getMovie().getDiscountCode() == DISCOUNT_REG){ discount = 0.9 } thisAmount = each.getMovie().getPriceCode() * each.getDaysRented() * discount;

27. 27 Refactoring 2  Extract method to getSumAmount()  It is relatively small, but since we need to copy the statement(), we should still extract this part to reduce duplication double totalAmount = 0;... totalAmount = totalAmount + thisAmount;

28. 28 Results  So statement() becomes  Looks much cleaner, less harmful to copy  May do some further refactoring by extract the header, footer, but may cause more complexity  No perfect solutions, just trade off public String statement() { String result = “Rental Record for “ + getName() + “\n”; for (Rental each : this.rentals) { result = result + each.getMovie.getName() + “ ” + each.getDaysRented() + “ ” + each.getAmount() + “\n”; } // add footer lines result = result + “Amount owed is “+ getSumAmount() + “\n”; return result; }

29. 29 Before applying refactoring  Finish the work at your hand  Usually bad smells come after you added a new feature or fixed a bug  Have a test suite  Make sure your code pass all test cases  Find out to what extent you can use automatic refactoring tools (which guarantees perserving behaviors)

30. 30 Automatic refactoring  Refactoring involves lots of changes  Any change may cause bugs in the software  So, Most IDEs provide automatic refactoring tools  Make sure that the program behavior does not change after the refactoring  Use automatic refactoring whenever possible  Don’t do it by yourself

31. 31 Behind automatic software refactoring tools  Automatic refactoring  Pre-conditions  e.g., the class you rename does not have a main method  e.g, the method you move should not have a side- effect on the class’s fields, otherwise the field must be visible by the moving destination  The transform  When pre-conditions are not satisfied, tools may refuse refactoring or give you choices

32. 32 Today’s class  API comments and Documentation  Javadoc  Software refactoring  Why software refactoring?  Types of refactoring  Tool supports  Behind refactoring tools  Software license  Proprietary licenses  Open source software licenses

33. 33 Software License  What is a license  A document accompanying with the software about an agreement of the user’s rights for using or doing other things to the software  For proprietary software  End-user license agreements (EULAs)  For open source software  GPL / LGPL  Apache  BSD  MIT

34. 34 Why licenses?  The specialty of software, compared to other publications  You often have to copy the software to use it, consider a multiple-CD/floppy disk game, hardware disposal, …  Section 117 of copyright Act: the owner of a software copy have the rights to copy the software to a computer for using purpose  General principle of copyrights: the owner of a copy can resell the copy without the agreement of the copyright owner: resell a book  So, basically, you can copy the software from the CD to your computer, and resell the CD…

35. 35 How software companies handle this?  We sell licenses, not software copies  So the users are not “owners of copies”  And they do not have the rights from section 117 of the Copyright Act  They only have the rights described in the license  That’s how software licenses come  A lot of legal issues, and cases  Apple vs. Franklin  MS vs. Harmony  MS vs. DAK  …

36. 36 Why care about licenses?  A recent news about the page 46 of ios7 user agreement Turn out to be a funny fake But should we care about licenses?

37. 37 Why care about software licenses?  If you work for a software company  As a developer, ask the department of legal issues before  Using any new tools for your software development, e.g., editing, checking, analysis, visualization, version control, …  Incorporating any code, or using any third-party library in the software you are developing  Especially careful about free and open source software  As a manager  May further need to consider what license to buy, how many to buy, according to the permissions in the licenses  How to design the license of your product

38. 38 Proprietary licenses  A agreement on how users can use the software  Who can use  certain person, the buyer: personal software  Any personal in a company/org: business software  How many users  1 installation  Fixed number of installations  Contract licenses  Period  Permanent  Annual

39. 39 Volume Licenses  A license given to a large company, government, or education institute  Allows large number of copies within the scope of the customer  A large fixed number or unlimited installations  Installation with one license key  The customer should keep license key confidential  And software provider may request to audit the usage of licenses

40. 40 License mechanisms  License keys  Server authentication  Hardware ID authentication after the first usage  Protecting the Licensing mechanism  Code obfuscation  Dynamic loaded code  encrypted code

41. 41 Open source licenses  A document accompany with the source code of open source software  Documenting the rights and responsibility of users or adapters  Users are required to accept the license before using the software  But usually, there is no mechanism to guarantee it

42. 42 Open source licenses  User rights  Use, copy, incorporate, revise, re-distribute, …  User responsibilities  Announce changes  Include license when re-distribute  Use certain license  Providing revised source code

43. 43 GPL (General Public License)  Most widely used license  Rights  All mentioned rights, including sell  Responsibilities  Providing source code when re-distribute  Re-distribute (any code including or revised from GPL licensed code) under GPL license  Ignore patents and regional rules (liberty or death)  So what will happen if I want to revise a GPL-licensed software, and then sell the revised software?

44. 44 GPL (General Public License)  Who is using GPL?  About 45% all os projects according to Black Duck  GNU software  gcc, glibc, emacs, …  Linux kernel  MySQL  OpenJDK (with classpath exception, why?)

45. 45 LGPL (Lesser-GPL)  A variant of GPL  Mostly the same with GPL  Dynamic and static link to LGPL libraries will not enforce your software to be LGPL  Who is using LGPL  QT  KDE  OpenOffice (once)  JBoss

46. 46 BSD  A license used for Berkeley Software Distribution (Free BSD operating system)  Rights: all mentioned rights, including sell  Responsibilities:  When re-distribution:  Including a copyright notice (both source and binary distributions)  Including an acknowledgement in ads  Needs permission to use the authors of the included BSD- software for promotion

47. 47 BSD  Who is using BSD?  Free BSD operating system  Google Chrome  OpenSSH  Bzip

48. 48 Apache  A license proposed by apache software foundation  Rights  Any mentioned rights, including sell  Responsibilities  Include apache license in the distributed software (both source and binary)  State changes in the changed source files  Including of the notice file if the Apache software you use includes one

49. 49 Apache  Who is using apache?  Apache software foundation  Ant, maven, log4j, tomcat, …  OpenOffice (now)  Android system  The Java part  Most open-source android apps

50. 50 Eclipse Public License  Software license used by eclipse, and many of its plugins  If just link to a EPL software library  Can use any license  No other requirements  If change and redistribute the code of EPL software  The new program must be open source, and can be distributed as binary code under any license compatible with EPL  The source code must under EPL

51. 51 Mozilla public license  A software license used by Mozilla software projects, firefox, thunderbird, etc.  Allow mixing of source files under different licenses  Changed MPL source files must still under MPL  CDDL (Common Development and Distribution License) is based on MPL  Open Solaris, Netbeans, Glassfish, …

52. 52 Types of licenses  Permissive licenses / business-friendly licenses  BSD  Apache  MIT  …  Copyleft licenses / business-unfriendly licenses  GPL  Somewhat between the two  LGPL  EPL  MPL  …

53. 53 Today’s class  API comments and Documentation  Javadoc  Software license  Proprietary licenses  Open source software licenses  Software refactoring  Why software refactoring?  Types of refactoring  Tool supports  Behind refactoring tools

54. 54 Next class  Unit testing  Drivers  Assertions  Documentation  Frameworks  JUnit and Demo  Parameterized Unit Testing

55. 55 Thanks!