java设计模式--[结构模式]--装饰者模式[decorator pattern]

一. 裝飾者模式

裝飾者模式,又叫包裝器,動態地給動象添加一些額外的職責,若要擴展功能,裝飾者指供了比繼承更有彈性的替代方案.

二. 裝飾者模式的UML類圖如下:
    

三. 本節內容以一個點餐配菜的案例來說明裝飾者模式的用法,完整代碼如下:

1.  主食類超類:

package structuralPattern.decorator.decorator2;
/**
 * @ClassName: StapleFood 
 * @Description:主食類[抽象組件]
 * @author Liyongbin
 * @date 2011-2-7 下午09:43:39 
 * @version V1.0
 */
public abstract class StapleFood {
	private String description ="Unknown StapleFood";
	/**
	 * 主食的描述[主食名稱]
	 * @return
	 */
	public String getDescription(){
		return description;
	}
	
	/**
	 * 主食的價格
	 * @return
	 */
	public abstract double cost();
}

2. 菜類的超類

package structuralPattern.decorator.decorator2;
/**
 * @ClassName: Dish 
 * @Description: 菜類
 * @author Liyongbin
 * @date 2011-2-7 下午09:53:11 
 * @version V1.0
 */
public abstract class Dish extends StapleFood {
	
	//繼承了主食類的描述[菜的名字]
	public abstract String getDescription() ;
}

3. 主食類的派生類_米飯類

package structuralPattern.decorator.decorator2;
/**
 * @ClassName: Rice 
 * @Description: 米飯_主食_具體組件
 * @author Liyongbin
 * @date 2011-2-7 下午09:56:26 
 * @version V1.0
 */
public class Rice extends StapleFood {

	@Override
	public String getDescription() {
		return "泰國香米";
	}
	
	@Override
	public double cost() {
		return 5.0;
	}
}

4. 主食類的派生類_面食類

package structuralPattern.decorator.decorator2;
/**
 * @ClassName: Rice 
 * @Description: 面飯_主食_具體組件
 * @author Liyongbin
 * @date 2011-2-7 下午09:56:26 
 * @version V1.0
 */
public class Noodle extends StapleFood {

	@Override
	public String getDescription() {
		return "面飯";
	}
	
	@Override
	public double cost() {
		return 4.0;
	}
}

5. 菜類的派生類: 雞肉

package structuralPattern.decorator.decorator2;

public class Chicken extends Dish {
	//
	private StapleFood stapleFood;

	//
	public Chicken(StapleFood stapleFood) {
		this.stapleFood = stapleFood;
	}

	主食的名稱+雞肉的名稱
	@Override
	public String getDescription() {
		return stapleFood.getDescription() + ",辣子雞";
	}

	//主食的價格+雞肉的價格
	@Override
	public double cost() {
		return stapleFood.cost()+12.0d ;
	}
}

6. 菜類的派生類: 魚肉

package structuralPattern.decorator.decorator2;

public class Fish extends Dish {
	//
	StapleFood stapleFood;

	//
	public Fish(StapleFood stapleFood) {
		this.stapleFood = stapleFood;
	}

	主食的名稱+魚肉的名稱
	@Override
	public String getDescription() {
		return stapleFood.getDescription() + ",烏江魚";
	}

	//主食的價格+魚肉的價格
	@Override
	public double cost() {
		return stapleFood.cost()+10.0d ;
	}
}

7. 菜類的派生類: 鴨肉

package structuralPattern.decorator.decorator2;

public class PekingDuck extends Dish {
	//
	StapleFood stapleFood;

	//
	public PekingDuck(StapleFood stapleFood) {
		this.stapleFood = stapleFood;
	}

	主食的名稱+鴨肉的名稱
	@Override
	public String getDescription() {
		return stapleFood.getDescription() + ",北京烤鴨";
	}

	//主食的價格+鴨肉的價格
	@Override
	public double cost() {
		return stapleFood.cost()+25.0d ;
	}
}

 8. 菜類的派生類: 羊肉

package structuralPattern.decorator.decorator2;

public class Mutton extends Dish {
	//
	StapleFood stapleFood;
	//
	public Mutton(StapleFood stapleFood) {
		this.stapleFood = stapleFood;
	}
	//主食的名稱+羊肉的名稱
	@Override
	public String getDescription() {
		return stapleFood.getDescription() + ",小肥羊";
	}
	//主食的價格+羊肉的價格
	@Override
	public double cost() {
		return stapleFood.cost()+30.0d ;
	}
}

 9. 點餐測試類

package structuralPattern.decorator.decorator2;
/**
 * @ClassName: DecoratorTest 
 * @Description:點餐測試
 * @author Liyongbin
 * @date 2011-2-7 下午09:12:46 
 * @version V1.0
 */
public class DecoratorTest {
	public static void main(String[] args) {
		//無菜面飯[￥4]
		StapleFood noodle0 = new Noodle();
		System.out.println(noodle0.getDescription()+" ￥"+noodle0.cost());
		
		//帶菜(雞肉[￥12],魚肉[￥10])面飯[￥4]
		StapleFood noodle1 = new Noodle();
		noodle1=new Chicken(noodle1);
		noodle1=new Fish(noodle1);
		System.out.println(noodle1.getDescription()+" ￥"+noodle1.cost());
		
		//無菜的米飯[￥5]
		StapleFood rice0 = new Rice();
		System.out.println(rice0.getDescription()+" ￥"+rice0.cost());
		
		//帶菜(雞肉[￥12],魚肉[￥10],羊肉[￥30],鴨肉[￥25])的米飯[￥5]
		StapleFood rice1 = new Rice();
		rice1=new Chicken(rice1);
		rice1=new Fish(rice1);
		rice1=new Mutton(rice1);
		rice1=new PekingDuck(rice1);
		System.out.println(rice1.getDescription()+" ￥"+rice1.cost());
	}
}

 10. 運行結果如下: