Java-马士兵设计模式学习笔记-观察者模式-读取properties文件,动态增加观察者

一、概述

1.目标：用observer.properties文件存储observer类，当要增加observer时，无需修改代码，修改properties文件即可

2.properties文件位置的关系：当properties文件放在src目录下时，由于编译会自动把src里的文件放到bin文件平，因此可用this.getClass.getClassLoader.getResourceAsStream(fileName)读取，当把properties文件放到包里时，则应加相应的包路径，如：

props.load(Test.class.getClassLoader().getResourceAsStream("com/tong/observer/observer.properties"));

PS:由于每次都要load properties文件(IO操作耗资源)，所以效率低，可考虑把相关IO操作的写成static块(单例模式)，在类装载时只load一次properties文件

二、代码

1.Test.java

class WakenUpEvent{
    
    private long time;
    private String location;
    private Child source;
    
    public WakenUpEvent(long time, String location, Child source) {
        super();
        this.time = time;
        this.location = location;
        this.source = source;
    }

    public long getTime() {
        return time;
    }

    public void setTime(long time) {
        this.time = time;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

    public Child getSource() {
        return source;
    }

    public void setSource(Child source) {
        this.source = source;
    }
    
    
}

class Child implements Runnable {
    
    private List<WakenUpListener> wakenUpListeners = new ArrayList<WakenUpListener>();
    
    public void addWakenUpListener(WakenUpListener wul){
        wakenUpListeners.add(wul);
    }
    public void wakeUp(){
        for(int i = 0; i < wakenUpListeners.size(); i++){
            WakenUpListener l = wakenUpListeners.get(i);
            l.actionToWakenUp(new WakenUpEvent(System.currentTimeMillis(), "bed", this));
        }
    }

    @Override
    public void run() {
        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        wakeUp();
    }
}


interface WakenUpListener {
    public void actionToWakenUp(WakenUpEvent e);
}

class Dad implements WakenUpListener {

    public void actionToWakenUp(WakenUpEvent e) {
        System.out.println("Fedd the child");
    }
    
}

class GrandFather implements WakenUpListener {

    public void actionToWakenUp(WakenUpEvent e) {
        System.out.println("抱孩子");
    }
    
}


public class Test {

    public static void main(String[] args) {
        
        Child c = new Child();
        
        Properties props = new Properties();
        try {
            props.load(Test.class.getClassLoader().getResourceAsStream("com/tong/observer/observer.properties"));
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        String [] observers = props.getProperty("observers").split(",");
        
        for(String s : observers){
            try {
                c.addWakenUpListener((WakenUpListener)Class.forName(s).newInstance());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        new Thread(c).start();
    }
}

2.observer.properties

 observers=com.tong.observer.Dad,com.tong.observer.GrandFather 

三、运行结果：