JAVA-MANI.BLOGSPOT.COM

In this example we'll listen to bean's property change event. We create a small bean named MyBean, adds attributes and getter/setter. We want to know or to get notified when the bean property name is changed.

First we need the add a PropertyChangeSupport field to the bean, with this object we will fire the property change event. When we need to listen for the change we have to create an implementation of a PropertyChangeListener. In this example we'll just use the MyBean class as the listener.

The PropertyChangeListener has a method called propertyChange and inside this method we'll implementing the code to get the event fired by the PropertyChangeSupport.



import java.beans.PropertyChangeSupport;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeEvent;
import java.io.Serializable;

public class MyBean implements PropertyChangeListener, Serializable {
private Long id;
private String name;

private PropertyChangeSupport pcs = new PropertyChangeSupport(this);

public MyBean() {
pcs.addPropertyChangeListener(this);
}

/**
* This method gets called when a bound property is changed.
*
* @param evt A PropertyChangeEvent object describing the event source
* and the property that has changed.
*/
public void propertyChange(PropertyChangeEvent evt) {
System.out.println("Name = " + evt.getPropertyName());
System.out.println("Old Value = " + evt.getOldValue());
System.out.println("New Value = " + evt.getNewValue());
}

public static void main(String[] args) {
MyBean bean = new MyBean();
bean.setName("My Initial Value");
bean.setName("My New Value");
bean.setName("My Yet Another Value");
}


//~ --------------------------------------------- Bean's Getters and Setters

public Long getId() {
return id;
}

public void setId(Long id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
String oldValue = this.name;
this.name = name;

//
// Fires a property change event
//
pcs.firePropertyChange("name", oldValue, name);
}
}