Java 装饰模式 （Decorator）

装饰模式

动态的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取代方案

代码

package gx.component;

/**
 * 组件：装饰类和被装饰类 都要继承：为了类型保持一致
 * @author always
 *
 */
public abstract class Component {

    public abstract void description();
    public abstract int cost();
}

package gx.component.impl;

import gx.component.Component;

/**
 * 装饰类的抽象类
 * @author always
 *
 */
public abstract class  Decorator extends Component{

    protected Component component;
}

package gx.component.impl;

import gx.component.Component;

/**
 *
 * 被包装的类
 * @author always
 *
 */
public class Phone extends Component{

    public void description() {
        System.out.println("裸机");
    }

    public int cost() {

        return 1900;
    }

}

package gx.decorator.impl;

import gx.component.Component;
import gx.component.impl.Decorator;

/**
 *
 * 装饰1：给手机买个壳
 * @author always
 *
 */
public class DaiKe extends Decorator{

    public DaiKe(){

    }

    public DaiKe(Component component){
        this.component=component;
    }
    public void description() {
        this.component.description();
        System.out.println("带了手机壳");
    }

    public int cost() {
        return 50+this.component.cost();
    }

}

package gx.decorator.impl;

import gx.component.Component;
import gx.component.impl.Decorator;

/**
 *
 * 装饰2：给手机贴个膜
 * @author always
 *
 */
public class TieMo extends Decorator{

    public TieMo(){}

    public TieMo(Component component){
        this.component=component;
    }

    public void description() {
        this.component.description();
        System.out.println("贴了膜");
    }

    public int cost() {
        return 20+this.component.cost();
    }

}

測试类：

package gx;

import gx.component.Component;
import gx.component.impl.Phone;
import gx.decorator.impl.DaiKe;
import gx.decorator.impl.TieMo;
import junit.framework.TestCase;

public class TestDecorator extends TestCase {

    public void testDecorator() {

        Component component = new TieMo(new DaiKe(new Phone()));

        component.description();
        System.out.println("价钱：" + component.cost());
        /*
         * 结果：
         *  裸机
         *  带了手机壳
         *  贴了膜
         *  价钱：1970
         */
    }
}