Software re-engineering vs reverse engineering Software re-engineering vs maintenance Software re-factoring

1. Software Engineering-L12
Sameera Gunathilaka
Lead Software Engineer
ERP Technical Consultant
IT1204 – Software Engineering Institute of Technology, University of Moratuwa 1

2. Software Forward
Engineering
• Forward engineering is a
process of constructing an
application with the help of the
general requirements of the
final implementation
• Building from a model into an
implementation language
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 2

3. Software Reverse Engineering
• Software Reverse Engineering is a process of recovering the design,
requirement specifications and functions of a product from an
analysis of its code
• A software which is needed to be upgrade or which is needed to be
shift to other operating system
• Reverse engineering is to recover the design and a specification from
implementation
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
3

4. Software Re-Engineering
• Software Re-Engineering is the
examination and alteration of a
system to reconstitute it in a
new form
• In Software Re-engineering, we
are improving the software to
make it more efficient and
effective.
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 4

5. Software Maintenance
• Software Maintenance is the process of modifying a software
product after it has been delivered to the customer.
• The main purpose of software maintenance is to modify and update
software application after delivery to correct faults and to improve
performance.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
5
Corrective Maintenance Adaptive Maintenance
Perfective Maintenance Preventive Maintenance

6. Software Refactoring
• The process of changing a software system in such a way that it does
not alter the external behaviour of the code yet improves its internal
structure
• Refactoring is intended to improve non-fuctional attributes of the
software.
• Code refactoring may help software developers discover and fix
hidden bugs
• Improve Code Readability
• Reduce complexity
• Improve source code maintainability
• Create expensive internal architecture
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 6

7. What’s Code
refactoring ?
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 7
Code
reorganization
Change the
structure not
the
behaviour
Cleans up “Code Smell”
Does NOT fix bugs

8. IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
8

9. IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 9

10. Code smell
• A code smell is a hint that something has gone wrong somewhere
in your code. Use the smell to track down the problem.
• Highly experienced and knowledgeable developers have a "feel"
for good design.
• Common Code Smells
• Duplicated Code
• Long method
• Long parameter list
• Switch Statements
• Improper Naming
• Comments
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 10

11. IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
11

12. IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
12

13. IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
13

14. Why do we
refactor?
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 14
Helps up deliver more business value faster
Improve the design of our software
Minimize the technical debt
Keep development at speed
Make the code easer to understand
To help find bugs in the maintenance phase

15. When should
we Refactor?
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 15
Add new functionality
• Refactor existing code until you
understand it
• Refactor design to make it simple
To find bugs
• Refactor to understand the code
For code reviews
• Immediate effect of code review
• Allows for higher level suggestions

16. What is meant
by Code
Review?
Code Review is a systematic
examination, which can find
and remove the
vulnerabilities in the code
such as memory leaks and
buffer overflows, conversion
issues, standards, readability.

17. IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 17

18. Common Code Review Approaches
• The Email Thread
• file is sent around to the appropriate colleagues via email
• Pair Programming
• working on the same code together and thereby checking each other’s work as
they go
• Over-the-Shoulder
• Once your code is ready, just find a qualified colleague to site down at your
workstation (or go to theirs) and review your code for you
• Tool-Assisted
• Software tools solve many of the limitations of the preceding approaches above,
tracking colleagues’ comments and proposed solutions to defects in a clear and
coherent sequence (similar to tracking changes in MS Word)
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
18

19. How do we Refactor?
•Manual Refactoring
•Code Smells
•Automated/Assisted Refactoring
•Refactoring by hands is time consuming
•Use IDE
IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 19

20. Tools for Code Review
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
20

21. Refactoring Techniques - Composing Methods
• Extract Method
You have a code fragment that can be grouped together.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
21

22. Refactoring Techniques - Composing Methods
• Extract Variable
• You have an expression that’s hard to understand.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
22

23. Refactoring Techniques - Composing Methods
• Replace Temp with Query
• You place the result of an expression in a local variable for later use in your
code.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
23

24. Refactoring Techniques - Composing Methods
• Remove Assignments to Parameters
• Some value is assigned to a parameter inside method’s body.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
24

25. Refactoring Techniques -
Moving Features between Objects
• Move Method
• A method is used more in another class than in its own class.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
25

26. Refactoring Techniques -
Moving Features between Objects
• Extract Class
• When one class does the work of two, awkwardness results.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
26

27. Refactoring Techniques -
Moving Features between Objects
• Remove Middle Man
• A class has too many methods that simply delegate to other objects.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
27

28. Refactoring Techniques - Organizing Data
• Change Reference to Value
• You have a reference object that’s too small and infrequently changed to
justify managing its life cycle.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
28

29. Refactoring Techniques - Organizing Data
• Replace Array with Object
• You have an array that contains various types of data.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
29

30. Refactoring Techniques - Organizing Data
• Change Unidirectional Association to Bidirectional
• You have two classes that each need to use the features of the other, but the
association between them is only unidirectional.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
30

31. Refactoring Techniques - Organizing Data
• Replace Type Code with Subclasses
• You have a coded type that directly affects program behavior (values of this
field trigger various code in conditionals).
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
31

32. Refactoring Techniques – Simplifying
conditional expressions
• Consolidate Duplicate Conditional Fragments
• Identical code can be found in all branches of a conditional.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
32

33. Refactoring Techniques – Simplifying
conditional expressions
• Replace Nested Conditional with Guard Clauses
• You have a group of nested conditionals and it’s hard to determine the normal
flow of code execution.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
33

34. IT1204 – Software Engineering Institute of Technology,
University of Moratuwa 34

35. Refactoring Techniques – Dealing with
Generalization
• Pull Up Field
• Two classes have the same field.
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
35

36. Thank you
IT1204 – Software Engineering
Institute of Technology, University of Moratuwa
36