Creational Patterns Part 2/5: Abstract Factory Pattern

Creational Patterns Part 2/5: Abstract Factory Pattern

目录

Creational Patterns Part 25 Abstract Factory Pattern

目录

Definition

UML Class Diagram

Implementation

Definition

Abstract Factory相当于一个超级工厂，这个工厂可以创建工厂，真可谓工厂的工厂。

在Abstract Factory Pattern中，有多个方法，每个方法产生一个工厂，每个产生的工厂又可以创建多个对象(Factory Pattern)。

何时使用？当希望可以同时控制几种对象的创建的时候，而Factory Pattern只可以控制一种对象的创建

使用频率：

High

UML Class Diagram

Implementation

在示例中Abstract Factory可以创建ShapeFactory和ColorFactory，然后再由两种工厂去创建各自的对象。用户根本不知道(不关心)对象是如何创建的。

// Shape.java
package designpatterns.creationalpatterns.abstractfactory;

public interface Shape {
void draw();
}

// Color.java
package designpatterns.creationalpatterns.abstractfactory;

public interface Color {
void fill();
}

// ShapeImpl.java
package designpatterns.creationalpatterns.abstractfactory;

class Circle implements Shape {

@Override
public void draw() {
System.out.println("Circle::draw()");
}

}

class Rectangle implements Shape {

@Override
public void draw() {
System.out.println("Rectangle::draw()");
}

}

class Square implements Shape {

@Override
public void draw() {
System.out.println("Shape::draw()");
}

}

// ColorImpl.java
package designpatterns.creationalpatterns.abstractfactory;

class Red implements Color {

@Override
public void fill() {
System.out.println("Red::fill()");
}
}

class Green implements Color {

@Override
public void fill() {
System.out.println("Green::fill()");
}
}

class Blue implements Color {

@Override
public void fill() {
System.out.println("Blue::fill()");
}
}

// AbstracFactory.java
package designpatterns.creationalpatterns.abstractfactory;

abstract class AbstractFactory {
abstract Shape getShape(String shape);
abstract Color getColor(String color);
}

class ShapeFactory extends AbstractFactory {

@Override
Shape getShape(String shapeType) {
if (shapeType == null)  return null;

if (shapeType.equalsIgnoreCase("CIRCLE")) {
return new Circle();
} else if (shapeType.equalsIgnoreCase("SQUARE")) {
return new Square();
} else if (shapeType.equalsIgnoreCase("RECTANGLE")) {
return new Rectangle();
}
return null;
}

@Override
Color getColor(String color) {
return null;
}
}

class ColorFactory extends AbstractFactory {

@Override
Shape getShape(String shapeType) {
return null;
}

@Override
Color getColor(String color) {
if (color == null)  return null;

if (color.equalsIgnoreCase("RED")) {
return new Red();
} else if (color.equalsIgnoreCase("GREEN")) {
return new Green();
} else if (color.equalsIgnoreCase("BLUE")) {
return new Blue();
}

return null;
}
}

// AbstractFactoryDemo.java
package designpatterns.creationalpatterns.abstractfactory;

public class AbstractFactoryDemo {
public static void main(String[] args) {
AbstractFactory absf = FactoryProduct.getFactory("Shape");

Shape shape = null;
shape = absf.getShape("Circle");
shape.draw();

shape = absf.getShape("Square");
shape.draw();

shape = absf.getShape("Rectangle");
shape.draw();

System.out.println("=================");

absf = FactoryProduct.getFactory("Color");
Color color = null;
color = absf.getColor("Red");
color.fill();

color = absf.getColor("Green");
color.fill();

color = absf.getColor("Blue");
color.fill();
}
}

class FactoryProduct {

public static AbstractFactory getFactory(String factory) {
if(factory.equalsIgnoreCase("SHAPE")) {
return new ShapeFactory();
} else if(factory.equalsIgnoreCase("COLOR")) {
return new ColorFactory();
}

return null;
}
}

// output
Circle::draw()
Shape::draw()
Rectangle::draw()
=================
Red::fill()
Green::fill()
Blue::fill()