设计模式 - 装饰者模式(Decorator Pattern) 具体解释

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.