CSE564 Lecture 16

Software Design
Builder
(202110)

Transcript

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   CSE 564
   Software Design
   Lecture 16: Builder
   Dr. Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   PERALTA 230U
   Office Hours: By appointment
   

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   Builder
   Wrapper of an object
   When an object cannot be produced in one step
   

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   GoF Patterns
   

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   Builder
   § A Builder is a wrapper of an object. It is used when an object cannot be
   produced in one single step.
   § Builder isolates the product’s internal representation and the steps for the
   product’s construction.
   § Use the Builder pattern to get rid of having a Product with multiple
   constructors with a diverse number of parameters each, i.e., as an option
   for providing default values for attributes in an object.
   

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   Builder
   

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   Builder pattern
   // For creating complex objects
   // Delegate to several builders
   public class Client {
   public static void main( string[] args ) {
   Director director = new Director( );
   StudentBuilder sBuilder = new StudentBuilder();
   InstructorBuilder iBuilder = new InstructorBuilder();
   director.constructStudent( sBuilder );
   Student s = sBuilder.getResult();
   s.show();
   director.constructInstructor( iBiulder );
   Instructor i = iBuilder.GetResult();
   i.Show();
   }
   }
   

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   Builder pattern
   class Director {
   public void constructStudent( Builder builder ) {
   builder.setSalary(“10”);
   builder.setAccess(“LIMITED”);
   builder.setHours(“20”);
   builder.setComputer(“no”);
   }
   public void constructInstructor( Builder builder ) {
   builder.setSalary(“50”);
   builder.setAccess(“FULL”);
   builder.setHours(“40”);
   builder.setComputer(“yes”);
   }
   }
   

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   Builder pattern
   interface Builder {
   void setSalary (String salary);
   void setAccess (String access);
   void setHours (String hours);
   void setComputer(String computer);
   }
   class StudentBuilder extends Builder {
   private int salary;
   private String access;
   private int hours);
   private Computer c;
   // setters for all variables
   public void setSalary (int salary) { this.salary = Integer.parseInt(salary)); }
   public void setAccess (String access) {this.access = access;}
   public void setHours (String hours) {this.hours = Integer.parseInt(hours)); }
   public void setComputer(String computer) {c = computer.equals(“yes”)?new Computer():null;}
   public Student getResult() {
   // you can validate here that all data exist
   return new Student (salary, access, hours, computer);
   }
   }
   

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   Builder pattern
   interface Builder {
   void setSalary (String salary);
   void setAccess (String access);
   void setHours (String hours);
   void setComputer(String computer);
   }
   class InstructorBuilder extends Builder {
   private int salary;
   private String access;
   private int hours;
   private Computer c;
   // setters for all variables
   public void setSalary (int salary) { this.salary = Integer.parseInt(salary)); }
   public void setAccess (String access) {this.access = access;}
   public void setHours (String hours) {this.hours = Integer.parseInt(hours)); }
   public void setComputer(String computer) {c = new Computer();}
   public Student getResult() {
   // you can validate here that all data exist
   return new Instructor (salary, access, hours, computer);
   }
   }
   

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    Builder pattern
    class Student {
    private int salary;
    private String access;
    private int hours;
    private Computer c;
    // common simple trivial getters
    // common simple trivial setters
    // common simple trivial constructor
    // what about making the constructor private ?
    }
    class Instructor {
    private int salary;
    private String access;
    private int hours;
    private Computer c;
    // common simple trivial getters
    // common simple trivial setters
    // common simple trivial constructor
    // what about making the constructor private ?
    }
    

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    Fluent-Builder
    Wrapper of an object
    When an object cannot be produced in one step
    

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    Fluent-Builder
    § The Fluent Builder is a builder whose design relies on method chaining. In
    doing so, it aims to promote code legibility.
    

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    Fluent-Builder
    import java.awt.*;
    public class Client {
    public static void main(String[] args) {
    FluentBuilder builder = new BoxFluentBuilder()
    .setColor(Color.RED)
    .setSize(20)
    .setX(10)
    .setY(20);
    Product box = ((BoxFluentBuilder)builder).get();
    }
    }
    

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    Fluent-Builder
    import java.awt.Color;
    public interface Builder {
    public Builder setColor(Color color);
    public Builder setSize(int size);
    public Builder setX(int x);
    public Builder setY(int y);
    }
    

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    Fluent-Builder
    import java.awt.*;
    public class BoxFluentBuilder implements FluentBuilder {
    private Color color;
    private int size, x, y;
    public Builder setColor (Color color) {
    this.color = color; return this;
    }
    public Builder setSize(int size) { this.size = size; return this; }
    public Builder setX(int x) { this.x = x; return this; }
    public Builder setY(int y) { this.y = y; return this; }
    public Box get() {
    return new Box (color, size, x, y);
    }
    }
    

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    Example
    

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    GoF Patterns
    

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    Factory
    Wrapper of a constructor
    One entire object to be built in a single method call
    

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    Abstract Factory
    

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    Products
    public interface Shape {
    void draw();
    }
    public class RoundedRectangle implements Shape {
    public void draw() {
    System.out.println("Inside RoundedRectangle/draw() method.");
    }
    }
    public class RoundedSquare implements Shape {
    public void draw() {
    System.out.println("Inside RoundedSquare/draw() method.");
    }
    }
    public class Rectangle implements Shape {
    public void draw() {
    System.out.println("Inside Rectangle/draw() method.");
    }
    }
    

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    Factories
    public abstract class AbstractFactory {
    Shape getShape(String shapeType) ;
    }
    public class ShapeFactory extends AbstractFactory {
    public Shape getShape(String shapeType){
    if(shapeType.equalsIgnoreCase("RECTANGLE")){
    return new Rectangle();
    }else if(shapeType.equalsIgnoreCase("SQUARE")){
    return new Square();
    }
    return null;
    }
    }
    

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    Factories
    public class RoundedShapeFactory extends AbstractFactory {
    public Shape getShape(String shapeType){
    if(shapeType.equalsIgnoreCase("RECTANGLE")){
    return new RoundedRectangle();
    }else if(shapeType.equalsIgnoreCase("SQUARE")){
    return new RoundedSquare();
    }
    return null;
    }
    }
    

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    Client
    public class Client {
    public static void main(String[] args) {
    AbstractFactory shapeFactory = new ShapeFactory();
    //get an object of Shape Rectangle
    Shape shape1 = shapeFactory.getShape("RECTANGLE");
    //call draw method of Shape Rectangle
    shape1.draw();
    //get an object of Shape Square
    Shape shape2 = shapeFactory.getShape("SQUARE");
    //call draw method of Shape Square
    shape2.draw(); ]
    //get shape factory
    AbstractFactory shapeFactory1 = new RoundedShapeFactory();
    //get an object of Shape Rectangle
    Shape shape3 = shapeFactory1.getShape("RECTANGLE");
    //call draw method of Shape Rectangle
    shape3.draw();
    //get an object of Shape Square
    Shape shape4 = shapeFactory1.getShape("SQUARE");
    //call draw method of Shape Square
    shape4.draw();
    }
    }
    

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    Questions
    

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    CSE 564 Software Design
    Javier Gonzalez-Sanchez, Ph.D.
    javiergs@asu.edu
    Fall 2021
    Copyright. These slides can only be used as study material for the class CSE564 at ASU.
    They cannot be distributed or used for another purpose.
    

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