Obverser觀察者模式二

方式三：更具備通用性，添加監聽事件（讓多個人同時監聽小孩醒來這個事件并作出相應動作，dad和mom就是觀察者）

class Dad implements WakeUpActionListener{
	@Override
	public void wakeUpAction(WakeUpEvent wakeUpEvent)
	{
		System.out.println("爸爸給小孩喂奶。。。");
		
	}
}
class Mom implements WakeUpActionListener{

	@Override
	public void wakeUpAction(WakeUpEvent wakeUpEvent)
	{
		System.out.println("媽媽給小孩喂奶");
		
	}
	
}
class WakeUpEvent{
	
}
interface WakeUpActionListener{
	 void wakeUpAction(WakeUpEvent wakeUpEvent);
}
class Child implements Runnable{
	private List<WakeUpActionListener> listenerLists=new ArrayList<WakeUpActionListener>();
	 void addListener(WakeUpActionListener l){
		listenerLists.add(l);
	}
	 void wakeUp(){
		 System.out.println("醒來了");
		 for(WakeUpActionListener l:listenerLists){
			 l.wakeUpAction(new WakeUpEvent());
		 }
	 }
	@Override
	public void run()
	{
		try
		{
			Thread.sleep(5000);
		} catch (InterruptedException e)
		{
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		wakeUp();
		
	}
}
public class Test
{
	public static void main(String[] args){
		Dad d=new Dad();
		Mom m=new Mom();
		Child c=new Child();
		c.addListener(d);
		c.addListener(m);
		new Thread(c).start();
	}
}
           

用屬性檔案管理Observers

檔案名observer.properties,裡面内容：observers=ObserverMode.Dad,ObserverMode.Mom

将上面代碼部分的main函數換成以下

public static void main(String[] args) throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException{
		Child c=new Child();
		Properties props=new Properties();
		//如果檔案放在src下直接可以寫檔案名，如果放在包下寫上路徑
		props.load(Test.class.getClassLoader().getResourceAsStream("ObserverMode/observer.properties"));
		String[] observers=props.getProperty("observers").split(",");
		for(String observer:observers){
			c.addListener((WakeUpActionListener)Class.forName(observer).newInstance());
		}
		new Thread(c).start();
	}
           

讀取硬碟換成單例模式：

public class Test
{
	public static void main(String[] args) throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException{
		Child c=new Child();
		//采用單例模式（優點：隻讀取一次硬碟；缺點：配置檔案更改不能立即生效）
		//緩存讀取效率非常高
		PropertiesManager props=new PropertiesManager();
		String[] observers=props.getProperties("observers").split(",");
		for(String observer:observers){
			c.addListener((WakeUpActionListener)Class.forName(observer).newInstance());
		}
		new Thread(c).start();
	}
}
class PropertiesManager{
	private static Properties props=new Properties();
	//靜态方法隻執行一次
	static{
		try
		{
			props.load(Test.class.getClassLoader().getResourceAsStream("ObserverMode/observer.properties"));
		} catch (IOException e)
		{
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public static String getProperties(String key){
		return props.getProperty(key);
	}
}