1. Reusability 11/29/2018© 2006 ITT Educational Services Inc.
Structured Programming: Unit 10 Slide 1

2. Objectives
Identify the benefits of building applications using frameworks.
Describe how a framework differs from a design pattern.
Use design patterns.
Identify the four elements that define a pattern
Use refactoring to improve code maintenance and reusability.
List the benefits of refactoring
Identify situations in which refactoring might cause problems
Write a program that uses the following components: Component Object Model (COM), ActiveX control, .NET component, JavaBean, Web service
Describe how you would use a COM object.
Describe how you would use an ActiveX control.
Describe how you would use a .NET component.
Describe how you would use a JavaBean
Describe how you woul use a Web service
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3. Patterns A pattern name The problem the pattern solves
Conditions that must be met for the pattern to be applicable
The solution to the problem brought by the pattern
Elements involved and their roles, responsibilities, relationships, and collaborations
Not a concrete design or implementation
The consequences of applying the pattern
Time and space
Language and implementation
Effects on flexibility, extensibility, and portability
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4. Observer Pattern 11/29/2018© 2006 ITT Educational Services Inc.
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5. Frameworks Provide abstract classes and base classes
Provide default implementations
Apply multiple patterns
Can be based on:
White box (classes and inheritance)
Black box (object composition)
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6. MVC Framework 11/29/2018© 2006 ITT Educational Services Inc.
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7. Java 2 Platform 11/29/2018© 2006 ITT Educational Services Inc.
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8. Java, the Language 11/29/2018© 2006 ITT Educational Services Inc.
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9. Java.awt.image Package 11/29/2018© 2006 ITT Educational Services Inc.
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10. Interfaces versus Classes
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11. JavaBeans Events Properties Introspection Customization Persistence
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12. JAR Files May include: A set of class files A set of serialize objects
Optional help files (HTML)
Optional localization information
Optional icons held in .icon files in GIF format
Other resources needed by the bean
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13. Basic Java Services Reflection Object serialization
Java native interface
Java AWT and JFC/Swing
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14. COM Component with a Single Interface
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15. COM Component with Multiple Interfaces
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16. Depiction of a COM Object
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17. COM Object Containment
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18. COM Object Aggregation
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19. ActiveX Controls COM objects, but with additional features
Self-registering
Handle events
Expose design-time properties
Support persistence
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20. .NET Common Type Systems
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21. Side-by-Side Interface Versioning
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22. COM Interoperability with .NET
COM Callable Wrapper
COM Application
.NET component
Runtime Callable Wrapper
.NET Application
COM component
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23. .NET Assemblies Shared assemblies
Stored in the Global Assembly Cache
Must be strong-named
Publisher policy
Application policy
Assemblies can also be private to an application
All assemblies require a manifest
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24. Refactoring – Key Points
Build a good set of tests before you start
Make a small change, then test
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25. Class Diagram of Starting Program
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26. Interactions for the Statement Method
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27. Refactoring First Example
public String statement() …
switch (each.getMovie().getPriceCode()){
case Movie.REGULAR:
thisAmount+=2
if(each.getaysRented() > 2)
thisAmount+= (each.getdaysRented -2) * 1.5;
break;
case Movie.NEW_RELEASE:
thisAmount+= each.getDaysRented()*3 }
Extract out into its own method
Pass each as a variable
Return thisAmount
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28. Rename Variables private double amountFor(Rental aRental) {
double result = 0;
switch (aRental.getMovie().getPriceCode()){
case Movie.REGULAR:
result +=2
if(aRental.getaysRented() > 2)
result += (aRental.getDaysRented -2) * 1.5;
break;
case Movie.NEW_RELEASE:
result += aRental.getDaysRented()*3
case Movie.CHILDRENS:
result += 1.5;
if (aRental.getDaysRented() > 3)
result += (aRental.getDaysRented()-3) * 1.5; }
return result;
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29. Move the Method to the Rental Class
double getCharge() {
double result = 0;
switch (aRental.getMovie().getPriceCode()){
case Movie.REGULAR:
result +=2
if(aRental.getaysRented() > 2)
result += (aRental.getDaysRented -2) * 1.5;
break;
case Movie.NEW_RELEASE:
result += aRental.getDaysRented()*3
case Movie.CHILDRENS:
result += 1.5;
if (aRental.getDaysRented() > 3)
result += (aRental.getDaysRented()-3) * 1.5; }
return result;
In Customer, delegate to the
new method and test
If it works, find calls to
the old method and
change them
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30. Class Diagram After the Move
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31. Replace the Conditional Logic with Polymorphism
Move the getCharge method to Movie
Pass daysRented
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32. Using Inheritance on Movie
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33. Using the State Pattern on Movie
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34. Interactions with the State Pattern
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35. Class Diagram after the State Pattern
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36. Why Refactor Improve software design
Make software easier to understand
Find bugs
Develop code more quickly
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37. When to Refactor If you do the same thing over and over
When you add functionality
When you need to fix a bug
During code review
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38. Potential Problems Databases Changing interfaces
Design changes that are hard to refactor
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39. Summary In this unit, students learned: Using patterns
Using frameworks
Using Java 2 Platform
Using JavaBeans
Using COM
Using ActiveX
Using .NET components
Using Web Services
Refactoring
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