GoF 23个经典的设计模式8--结构模式之 Composite组合模式（未完代续）

Composite组合模式：将对象以树的结构组合到一个总的层次中。组合模式让客户端以统一的格式应用独立的对象和组合体。
Compose objects into tree structures to represent whole-part hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly. [GoF, p163]

其实组合模式可以说是树型模式，一个节点算是一个对象。该节点可以再有和自己相同的子节点。



这又有点是低归的意思，看上去是自己拥有自己。

我们来组装一个PC把，首先这个PC由统一定义的接口的部件组成，所以每个部件的接口都是一样的，客户可以不用管什么部件，只要往上装就是了。

先看客户端：


package org.benewu.patterns.composite;






public class Client ...{






public static void main(String[] args) ...{




PCComposite myPC = new PCComposite();


myPC.setName("myPC");




//装入主板


PCComposite mainBroad = new PCComposite();


mainBroad.setPrice(800);


mainBroad.addPart(myPC);


mainBroad.setName("mainBroad");




//装入硬盘


PCComposite hardDesc = new PCComposite();


hardDesc.setPrice(1600);


hardDesc.addPart(mainBroad);


hardDesc.setName("hardDesc");




//装入CPU


PCComposite cpu = new PCComposite();


cpu.setPrice(2000);


cpu.addPart(mainBroad);


cpu.setName("cpu");




//装入USB管理器


PCComposite usbComposite = new PCComposite();


usbComposite.setPrice(100);


usbComposite.addPart(mainBroad);


usbComposite.setName("usbComposite");




//装入闪存


PCComposite flashDesc = new PCComposite();


flashDesc.setPrice(200);


flashDesc.addPart(usbComposite);


flashDesc.setName("flashDesc");




//装入视频头


PCComposite videoCam = new PCComposite();


videoCam.setPrice(300);


videoCam.addPart(usbComposite);


mainBroad.setName("mainBroad");




//装入新的视频头


PCComposite newVideoCam = new PCComposite();


newVideoCam.setPrice(350);


newVideoCam.addPart(usbComposite);


newVideoCam.setName("newVideoCam");




//打印总价格


System.out.println("myPC price is :"+myPC.getTotalPrice());




//卸载视频头


videoCam.removePart(usbComposite);


System.out.println("myPC price is : +"myPC.getTotalPrice());




//打印全部部件


myPC.printAll();




}




}



代码看上去很多，其实只作了两件事情，一，装入部件，二，察看部件内容。

再看部件的定义，首先定义通用的元素接口：


package org.benewu.patterns.composite;






public interface Elements ...{




public void add(Elements e);


public void remove(Elements e);


}



然后定义电脑部件的接口，它有id,name,price等属性


package org.benewu.patterns.composite;




import java.util.ArrayList;


import java.util.List;






public abstract class Component implements Elements ...{




private String partId;




private Integer price;




private String name;




private Component parent;






public void removePart(String id) ...{






for (Component component : components) ...{




if (id.equals(component.getPartId())) ...{


remove(component);


}


}


}






public void add(Elements e) ...{


components.add((Component) e);


}






public void remove(Elements e) ...{


components.remove(e);


}






public Integer getPrice() ...{


return price;


}






public Integer getTotalPrice() ...{


Integer totalPrice = null;




if (price == null) ...{


totalPrice = new Integer(0);




} else ...{


totalPrice = price;




}






for (Component component : components) ...{


totalPrice += component.getTotalPrice();


}


return totalPrice;


}




protected List<Component> components = new ArrayList<Component>();






public void setPrice(Integer price) ...{




this.price = price;


}






public String getPartId() ...{


return partId;


}






public void setPartId(String partId) ...{


this.partId = partId;


}






public List<Component> getComponents() ...{


return components;


}




public abstract void printAll();






public String getName() ...{


return name;


}






public void parentPrint() ...{




if (getParent() != null) ...{


System.out.print("--");


getParent().parentPrint();




} else ...{


System.out.print("-");


}


}






public void setName(String name) ...{


this.name = name;


}






public Component getParent() ...{


return parent;


}






public void setParent(Component parent) ...{


this.parent = parent;


}


}



最后实现电脑部件：


package org.benewu.patterns.composite;




import java.util.List;






public class PCComposite extends Component ...{








public void addPart(PCComposite part)...{


part.add(this);


this.setParent(part);


}






public void setPrice(Integer price) ...{




super.setPrice(price);


}






public void removePart(PCComposite composite) ...{




composite.remove(this);


}








public void printAll()...{


parentPrint();


System.out.print(getName());




if(getPrice()!= null)...{


System.out.println(" : " +getPrice());




}else...{


System.out.println();


}


List<Component> comps = getComponents();




if(comps != null && comps.size() >0)...{




for (Component component : comps) ...{


component.printAll();


}


}


}


}



组合模式用到迭代方法，可能粗看起来比较复杂。

参考：http://home.earthlink.net/~huston2/dp/patterns.html：