Bridge Pattern

Bridge Pattern에 대해 설명하는 페이지입니다.

Posted Dec 13, 2023

By HyunJinNo

Tags

Design Pattern, Java

1. Introduction

• Purpose
  • Defines an abstraction object structure independently of the implementation object structure in order to limit coupling.
• Use When
  • Abstractions and implementations should not be bound at compile time.
  • Abstractions and implementations should be independently extensible.
  • Implementation details should be hidden from the client.

2. Characteristics

• Separate the variations in abstraction from the variations in implementation so that the number of classes only grows linearly.
• Decouples an abstraction from its implementation so that the two can vary independently.

3. Participants

• Abstraction
  • defines the abstraction's interface
  • maintains a reference to the implementor
  • forwards requests to the implementor (collaboration)
• RefinedAbstraction
  • extends abstraction interface
• Implementor
  • defines interface for implementations
• ConcreteImplementor
  • implements Implementor interface, i.e. defines an implementation

4. How to Use (Example)

• Abstraction

  java

  1public abstract class Shape {
  2    private Drawing dp;
  3
  4    public Shape(Drawing dp) {
  5        this.dp = dp;
  6    }
  7
  8    public abstract void draw();
  9
  10    public void drawLine(double x1, double y1, double x2, double y2) {
  11        this.dp.drawLine(x1, y1, x2, y2);
  12    }
  13
  14    public void drawCircle(double x, double y, double r) {
  15        this.dp.drawCircle(x, y, r);
  16    }
  17}

• RefinedAbstraction

  java

  1public class Rectangle extends Shape {
  2    private double x1;
  3    private double y1;
  4    private double x2;
  5    private double y2;
  6
  7    public Rectangle(Drawing dp, double x1, double y1, double x2, double y2) {
  8        super(dp);
  9        this.x1 = x1;
  10        this.y1 = y1;
  11        this.x2 = x2;
  12        this.y2 = y2;
  13    }
  14
  15    @Override
  16    public void draw() {
  17        drawLine(x1, y1, x2, y1);
  18        drawLine(x2, y1, x2, y2);
  19        drawLine(x2, y2, x1, y2);
  20        drawLine(x1, y2, x1, y1);
  21    }
  22}

  java

  1public class Circle extends Shape {
  2    private double x;
  3    private double y;
  4    private double r;
  5
  6    public Circle(Drawing dp, double x, double y, double r) {
  7        super(dp);
  8        this.x = x;
  9        this.y = y;
  10        this.z = z;
  11    }
  12
  13    public void draw() {
  14        drawCircle(x, y, r);
  15    }
  16}

• Implementor

  java

  1public abstract class Drawing {
  2    public abstract void drawLine(double x1, double y1, double x2, double y2);
  3    public abstract void drawCircle(double x, double y, double r);
  4}

• ConcreteImplementor

  java

  1public class V1Drawing extends Drawing {
  2    public void drawLine(double x1, double y1, double x2, double y2) {
  3        DP1.draw_a_line(x1, y1, x2, y2);
  4    }
  5
  6    public void drawCircle(double x, double y, double r) {
  7        DP1.draw_a_circle(x, y, r);
  8    }
  9}

  java

  1public class V2Drawing extends Drawing {
  2    public void drawLine(double x1, double y1, double x2, double y2) {
  3        DP2.drawLine(x1, y1, x2, y2);
  4    }
  5
  6    public void drawCircle(double x, double y, double r) {
  7        DP2.drawCircle(x, y, r);
  8    }
  9}