HELLOWORLD级事件属性监听小技巧,随便写了点测试代码[转]

首先,定义一个基类,负责加入监听者,


package net.cafe;




import java.beans.PropertyChangeSupport;


import java.beans.PropertyChangeListener;






/** *//**


* Created by IntelliJ IDEA.


* User: JJYAO


* Date: 2004-11-1


* Time: 23:01:56


* To change this template use File | Settings | File Templates.


*/




public class BaseEventBean ...{




protected PropertyChangeSupport pcs;






public void addPropertyChangeListener(PropertyChangeListener listener)...{




if(pcs == null)...{


pcs = new PropertyChangeSupport(this);


}


pcs.addPropertyChangeListener(listener);


}






public void removeChangeListener(PropertyChangeListener listener) ...{




if(pcs != null)...{


pcs.removePropertyChangeListener(listener);


}


}




}

一个POJO继承这个类,并在SET方法里添加触发事件的方法


package net.cafe;






/** *//**


* Created by IntelliJ IDEA.


* User: JJYAO


* Date: 2004-11-1


* Time: 23:15:34


* To change this template use File | Settings | File Templates.


*/




public class FoolBean extends BaseEventBean ...{




private String userName;


private String password;






public String getPassword() ...{


return password;


}






public void setPassword(String newPassword) ...{


String oldPassword = password;


this.password = newPassword;


pcs.firePropertyChange("password",oldPassword,password);


}






public String getUserName() ...{


return userName;


}






public void setUserName(String userName) ...{


this.userName = userName;


}




}

属性监听者


package net.cafe;




import java.beans.PropertyChangeListener;


import java.beans.PropertyChangeEvent;






/** *//**


* Created by IntelliJ IDEA.


* User: JJYAO


* Date: 2004-11-1


* Time: 23:12:33


* To change this template use File | Settings | File Templates.


*/




public class Listener implements PropertyChangeListener ...{






public void propertyChange(PropertyChangeEvent evt) ...{


System.out.println("==========old value=========" + evt.getOldValue()) ;


System.out.println("==========new Value========" + evt.getNewValue());


}


}

测试代码


package net.cafe;






/** *//**


* Created by IntelliJ IDEA.


* User: JJYAO


* Date: 2004-11-1


* Time: 23:24:28


* To change this template use File | Settings | File Templates.


*/




public class BeanEventTest ...{






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


FoolBean bean = new FoolBean();


bean.addPropertyChangeListener(new Listener());


bean.setPassword("22222");


bean.setPassword("33333");


}


}

BTW,SUN的java.beans.*包含了大多空包，这些方法都需要自己扩展,我们完全不需要用它定义的方法名。
上面的例子完全可以用自己的方法来实现.

通过这个例子，可以方便的构建一个GUI的事件监听类。业务处理层只需要处理数据，而GUI监听器负责将数据更新到界面上。