CSC308 Lecture 16

Software Engineering I
Design Patterns - Decorator/Composite
(202211)

Transcript

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   CSC 308
   Software Engineering 1
   Lecture 16:
   Design Patterns – Decorator/Composite
   Dr. Javier Gonzalez-Sanchez
   javiergs@calpoly.edu
   www.javiergs.com
   Building 14 -227
   Office Hours: By appointment
   

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   CSC 308
   Software Engineering I
   Lecture 16: Design Patterns – Decorator/Composite
   Dr. Javier Gonzalez-Sanchez
   javiergs@calpoly.edu
   users.csc.calpoly.edu/~javiergs | javiergs.com
   Building 14 -227
   Office Hours: By appointment
   

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   Previously …
   Design Patterns
   

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   GoF Patterns
   

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   Singleton
   

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   class MainApp {
   public static void Main(String []a){
   // Constructor is protected -- cannot use new
   Singleton s1 = Singleton.getInstance();
   Singleton s2 = Singleton.getInstance();
   // Test for same instance
   if (s1 == s2){
   // true - Objects are the same instance
   }
   }
   }
   Singleton
   

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   class Singleton{
   private static Singleton _instance;
   // Constructor is 'protected'
   protected Singleton() {}
   public static Singleton getInstance(){
   if (_instance == null){
   _instance = new Singleton();
   }
   return _instance;
   }
   }
   Singleton
   

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   Decorator & Composite
   Design Patterns
   

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   GoF Patterns
   

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    Decorator
    

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    Decorator
    

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    Decorator
    

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    abstract class Component {
    public abstract void operation();
    }
    Component
    

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    class ConcreteComponent extends Component {
    @override
    public void operation() {
    System.out.print("ConcreteComponent-Operation()");
    }
    }
    ConcreteComponent
    

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    abstract class Decorator extends Component {
    protected Component component;
    public void setComponent(Component component) {
    this.component = component;
    }
    @override
    public void operation() {
    if (component != null) {
    component.operation();
    }
    }
    }
    Decorator
    

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    class ConcreteDecoratorA extends Decorator {
    @override
    public void operation() {
    super.operation();
    System.out.println("ConcreteDecoratorA-Operation()”);
    }
    }
    ConcreteDecoratorA
    

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    class ConcreteDecoratorB extends Decorator {
    @override
    public void operation() {
    super.operation();
    addedBehavior();
    System.out.println("ConcreteDecoratorB-Operation()");
    }
    void addedBehavior() {
    }
    }
    ConcreteDecoratorB
    

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    class MainApp {
    static void main() {
    // Create ConcreteComponent and two Decorators
    ConcreteComponent c = new ConcreteComponent();
    ConcreteDecoratorA d1 = new ConcreteDecoratorA();
    ConcreteDecoratorB d2 = new ConcreteDecoratorB();
    // Link decorators
    d1.SetComponent(c);
    d2.SetComponent(d1);
    d2.Operation();
    }
    }
    Main
    

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    class MainApp {
    static void main() {
    // Create ConcreteComponent and two Decorators
    ConcreteComponent c = new ConcreteComponent();
    ConcreteDecoratorA d1 = new ConcreteDecoratorA();
    ConcreteDecoratorB d2 = new ConcreteDecoratorB();
    // Link decorators
    d1.SetComponent(c);
    d2.SetComponent(d1);
    d2.Operation();
    }
    }
    Main
    ConcreteComponent - Operation()
    ConcreteDecoratorA - Operation()
    ConcreteDecoratorB - Operation()
    

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    § Both allow you to change how an object behaves
    § The decorator pattern can be used to make it possible to extend (decorate)
    the functionality of a certain object at runtime.
    § Inheritance adds behavior at compilation-time.
    Decorator vs Inheritance
    

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    Scenario
    CompanionHelper
    CompanionTroll
    Companion
    

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    Scenario
    CompanionHelper
    CompanionTroll
    Companion
    CompanionTrollHelper
    

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    Scenario
    CompanionHelper
    CompanionTroll
    Companion
    CompanionTrollHelper
    

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    Example 1
    Text Mode
    

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    Decorator
    

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    Main
    

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    public interface Companion {
    public void doSomething();
    }
    Companion
    

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    public class BasicCompanion implements Companion {
    @Override
    public void doSomething() {
    System.out.print("Hello Student, ");
    }
    }
    BasicCompanion
    

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    public class CompanionDecorator implements Companion {
    protected Companion c;
    public void add(Companion c){
    this.c = c;
    }
    @Override
    public void doSomething() {
    this.c.doSomething();
    }
    }
    CompanionDecorator
    

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    public class HelperCompanion extends CompanionDecorator {
    @Override
    public void doSomething(){
    super.doSomething();
    System.out.print(" I am here to help you. ");
    }
    }
    HelperCompanion
    

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    public class AffectiveCompanion extends CompanionDecorator {
    @Override
    public void doSomething(){
    super.doSomething();
    System.out.print(" I am here to cheer you.");
    }
    }
    AffectiveCompanion
    

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    Main
    

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    Questions
    

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    Office Hours
    Tuesday and Thursday 3 - 5 pm
    But an appointment required
    Sent me an email – javiergs@calpoly.edu
    

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    CSC 308
    Software Engineering 1
    Lab 16:
    Design Patterns
    Dr. Javier Gonzalez-Sanchez
    javiergs@calpoly.edu
    www.javiergs.com
    Building 14 -227
    Office Hours: By appointment
    

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    Test Yourselves
    Class Diagram
    

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    Scenario
    

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    Let’s Work
    

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    CSC 308 Software Engineering I
    Javier Gonzalez-Sanchez, Ph.D.
    javiergs@calpoly.edu
    Winter 2023
    Copyright. These slides can only be used as study material for the class CSC308 at Cal Poly.
    They cannot be distributed or used for another purpose.
    

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