设计模式（2）：抽象工厂模式

在抽象工厂模式中，接口负责创建相关对象的工厂，而不明确指定它们的类。 每个生成的工厂可以按照工厂模式提供对象。

1.创建Shape的接口

public interface Shape {
   void draw();
}

2.创建实现相同接口的具体类

public class Rectangle implements Shape {

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

public class Square implements Shape {

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

public class Circle implements Shape {

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

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 3.创建一个Colors接口

public interface Color {
   void fill();
}

4.创建实现相同接口的具体类

public class Red implements Color {

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

public class Green implements Color {

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

public class Blue implements Color {

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

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5.创建实现相同接口的具体类

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

6.创建实现相同接口的具体类。

创建工厂类，根据给定信息扩展AbstractFactory以生成具体类的对象

public class ShapeFactory extends AbstractFactory {

   @Override
   public Shape getShape(String shapeType){

      if(shapeType == null){
         return null;
      }

      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();

      }else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();

      }else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }

      return null;
   }

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

public class ColorFactory extends AbstractFactory {

   @Override
   public 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;
   }
}

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7.创建工厂生成器/生产器类，通过传递如Shape或Color等信息来获取工厂

public class FactoryProducer {
   public static AbstractFactory getFactory(String choice){

      if(choice.equalsIgnoreCase("SHAPE")){
         return new ShapeFactory();

      }else if(choice.equalsIgnoreCase("COLOR")){
         return new ColorFactory();
      }

      return null;
   }
}

8.使用FactoryProducer来获取AbstractFactory，以便通过传递类型等信息来获取具体类的工厂

public class AbstractFactoryPatternDemo {
   public static void main(String[] args) {

      //get shape factory
      AbstractFactory shapeFactory = FactoryProducer.getFactory("SHAPE");

      //get an object of Shape Circle
      Shape shape1 = shapeFactory.getShape("CIRCLE");

      //call draw method of Shape Circle
      shape1.draw();

      //get an object of Shape Rectangle
      Shape shape2 = shapeFactory.getShape("RECTANGLE");

      //call draw method of Shape Rectangle
      shape2.draw();

      //get an object of Shape Square 
      Shape shape3 = shapeFactory.getShape("SQUARE");

      //call draw method of Shape Square
      shape3.draw();

      //get color factory
      AbstractFactory colorFactory = FactoryProducer.getFactory("COLOR");

      //get an object of Color Red
      Color color1 = colorFactory.getColor("RED");

      //call fill method of Red
      color1.fill();

      //get an object of Color Green
      Color color2 = colorFactory.getColor("Green");

      //call fill method of Green
      color2.fill();

      //get an object of Color Blue
      Color color3 = colorFactory.getColor("BLUE");

      //call fill method of Color Blue
      color3.fill();
   }
}

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9.验证输出

Inside Circle::draw() method. Inside Rectangle::draw() method. Inside Square::draw() method. Inside Red::fill() method. Inside Green::fill() method. Inside Blue::fill() method.