装饰者模式(Decorator Pattern) 具体解释

本文地址: http://blog.csdn.net/caroline_wendy/article/details/26707033

装饰者模式(Decorator Pattern):动态地将责任附加到对象上. 若要扩展功能, 装饰者提供了比继承更有弹性的替代方案.

用法:

1. 首先创建组件(Component)父类, 全部类,详细组件(Concrete Component)和装饰者(Decorator)都属于这一类型,
能够进行扩展;

能够是抽象类(abstract class), 也能够是接口(interface);

代码:

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public abstract class Beverage {

	String description = "Unkown Beverage";

	public String getDescription() {

		return description;

	}

	public abstract double cost();

}

2. 装饰者(Decorator)类父类, 继承组件(component)父类, 可是不要实现接口函数, 由它的继承类(详细的装饰者)去实现,

能够是抽象类(abstract class),
也能够是接口(interface);

代码:

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public abstract class CondimentDecorator extends Beverage {

	public abstract String getDescription();

}

3. 详细组件(Concrete Component), 即装饰者(Decorator)须要装饰的基础, 继承组件(Component)父类;

代码:

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class DarkRoast extends Beverage {

	public DarkRoast() {

		description = "Dark Roast";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 0.99;

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Decat extends Beverage {

	public Decat() {

		description = "Decat";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 1.05;

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Espresso extends Beverage {

	public Espresso() {

		description = "Espresso";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 1.99;

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class HouseBlend extends Beverage {

	public HouseBlend() {

		description = "House Blend Coffee";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return .89;

	}

}

4. 装饰者(Decorator)类继承装饰者父类, 实现组件父类的接口和装饰者父类的接口.

代码:

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Milk extends CondimentDecorator {

	Beverage beverage;

	public Milk(Beverage beverage) {

		this.beverage = beverage;

	}

	/* (non-Javadoc)

	 * @see decorator.CondimentDecorator#getDescription()

	 */

	@Override

	public String getDescription() {

		// TODO Auto-generated method stub

		return beverage.getDescription() + ", Milk";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 0.10 + beverage.cost();

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Mocha extends CondimentDecorator {

	Beverage beverage;

	public Mocha(Beverage beverage) {

		this.beverage = beverage;

	}

	/* (non-Javadoc)

	 * @see decorator.CondimentDecorator#getDescription()

	 */

	@Override

	public String getDescription() {

		// TODO Auto-generated method stub

		return beverage.getDescription() + ", Mocha";

	}

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 0.20+beverage.cost();

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Soy extends CondimentDecorator {

	Beverage beverage;

	public Soy(Beverage beverage) {

		this.beverage = beverage;

	} 

	/* (non-Javadoc)

	 * @see decorator.CondimentDecorator#getDescription()

	 */

	@Override

	public String getDescription() {

		// TODO Auto-generated method stub

		return beverage.getDescription() + ", Soy";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 0.15 + beverage.cost();

	}

}

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class Whip extends CondimentDecorator {

	Beverage beverage;

	public Whip(Beverage beverage) {

		this.beverage = beverage;

	}

	/* (non-Javadoc)

	 * @see decorator.CondimentDecorator#getDescription()

	 */

	@Override

	public String getDescription() {

		// TODO Auto-generated method stub

		return beverage.getDescription() + ", Whip";

	}

	/* (non-Javadoc)

	 * @see decorator.Beverage#cost()

	 */

	@Override

	public double cost() {

		// TODO Auto-generated method stub

		return 0.10 + beverage.cost();

	}

}

5. 測试, 创建详细组件(Concrete Component), 再一层一层加入装饰者(Decorator)类, 能够实现动态的组合;

代码:

/**

 * @time 2014年5月23日

 */

package decorator;

/**

 * @author C.L.Wang

 *

 */

public class StarbuzzCoffee {

	/**

	 * @param args

	 */

	public static void main(String[] args) {

		// TODO Auto-generated method stub

		Beverage beverage = new Espresso();

		System.out.println(beverage.getDescription() +

				" $" + beverage.cost());

		Beverage beverage2 = new DarkRoast();

		beverage2 = new Mocha(beverage2);

		beverage2 = new Mocha(beverage2);

		beverage2 = new Whip(beverage2);

		System.out.println(beverage2.getDescription() +

				" $" + beverage2.cost());

		Beverage beverage3 = new HouseBlend();

		beverage3 = new Soy(beverage3);

		beverage3 = new Mocha(beverage3);

		beverage3 = new Whip(beverage3);

		System.out.println(beverage3.getDescription() +

				" $" + beverage3.cost());

	}

}

6. 输出:

Espresso $1.99

Dark Roast, Mocha, Mocha, Whip $1.49

House Blend Coffee, Soy, Mocha, Whip $1.34

面向对象的原则:

对扩展开发, 对改动关闭.