（译）JAVA设计模式【二】——抽象工厂模式

抽象工厂模式一般有一个超级工厂，这个工厂能够创建其它的工厂，也被称为"工厂的工厂"。同简单工厂模式样，这种设计模式也属于创造模式
实现
首先，定义接口Shape，以及其实现类。
其次，定义一个抽象工厂类AbstractFactory。工厂类ShapeFactory以及RoundedShapeFactory继承这个抽象类。FactoryProducer就是创建其它工厂的工厂类。
最后，我们的demo类AbstractFactoryPatternDemo使用超级工厂FactoryProducer来获取AbstractFactory对象（ShapeFactory或者RoundedShapeFactory对象）

下面用一张UML类图来说明这种关系

1. 定义接口

public interface Shape {
   void draw();
}

2. 定义接口的实现类

RoundedRectangle.java

public class RoundedRectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedRectangle::draw() method.");
   }
}

RoundedSquare.java

public class RoundedSquare implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedSquare::draw() method.");
   }
}

Rectangle.java

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

Square.java

public class Square implements Shape {
    public void draw() {
        System.out.println("Inside Square::draw() method.");
    }
}

Rectangle.java

public class Rectangle implements Shape {
    public void draw() {
        System.out.println("Inside Rectangle::draw() method.");
    }
}

3. 定义抽象工厂类

. AbstractFactory.java

public abstract class AbstractFactory {
   abstract Shape getShape(String shapeType) ;
}

4. 定义工厂类继承抽象工厂类,根据传入的参数生成不同的对象。

ShapeFactory.java

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

RoundedShapeFactory.java

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

5. 定义超级工厂类，也就是工厂的工厂

可以根据入参的不同，生成不同的工厂实例。
FactoryProducer.java

ublic class FactoryProducer {
    //根据参数，产生不同的工厂实例
   public static AbstractFactory getFactory(boolean rounded){   
      if(rounded){
         return new RoundedShapeFactory();         
      }else{
         return new ShapeFactory();
      }
   }
}

6. 定义demo类

AbstractFactoryPatternDemo.java

public class AbstractFactoryPatternDemo {
   public static void main(String[] args) {
      //get rounded shape factory
      AbstractFactory shapeFactory = FactoryProducer.getFactory(false);
      //get an object of Shape Rounded Rectangle
      Shape shape1 = shapeFactory.getShape("RECTANGLE");
      //call draw method of Shape Rectangle
      shape1.draw();
      //get an object of Shape Rounded Square 
      Shape shape2 = shapeFactory.getShape("SQUARE");
      //call draw method of Shape Square
      shape2.draw();
      //get rounded shape factory
      AbstractFactory shapeFactory1 = FactoryProducer.getFactory(true);
      //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();
      
   }
}

7. 运行结果

Inside Rectangle::draw() method.
Inside Square::draw() method.
Inside RoundedRectangle::draw() method.
Inside RoundedSquare::draw() method.