java.beans.PropertyChangeListener (interface) 
java.beans.PropertyChangeSupport (class)
java.beans.PropertyChangeEvent (class)
java.beans.PropertyChangeListener

public void propertyChange(PropertyChangeEvent evt) {  
// TODO Auto-generated method stub  
} 

 java.beans.PropertyChangeSupport 

public PropertyChangeSupport(Object sourceBean) 

private PropertyChangeSupport listeners = new PropertyChangeSupport(this); 

public void addPropertyChangeListener(PropertyChangeListener listener) 

public void removePropertyChangeListener(PropertyChangeListener listener) 

public void firePropertyChange(PropertyChangeEvent evt)  
 
public void firePropertyChange(String propertyName,  
                boolean oldValue,  
                boolean newValue)  
 
public void firePropertyChange(String propertyName,  
                int oldValue,  
                int newValue)  
 
public void firePropertyChange(String propertyName,  
                Object oldValue,  
                Object newValue) 

java.beans.PropertyChangeEvent

public String getPropertyName()  
public Object getNewValue()  
public Object getOldValue() 

public class Domain{  
  protected String id;  
  protected String name;  
  protected String desName;  
 
  protected PropertyChangeSupport listeners = new PropertyChangeSupport(this);  
 
  public String getId() {  
    return id;  
  }  
 
  public void setId(String id) {  
    this.id = id;  
    firePropertyChange("Domain.id", null, id);  
  }  
 
  public String getDesName() {  
    return desName;  
  }  
 
  public void setDesName(String desName) {  
    this.desName = desName;  
    firePropertyChange("Domain.desName", null, desName);  
  }  
 
  public String getName() {  
    return name;  
  }  
 
  public void setName(String name) {  
    this.name = name;  
    firePropertyChange("Domain.name", null, name);  
  }  
 
  public void addPropertyChangeListener(PropertyChangeListener listener) {  
    listeners.addPropertyChangeListener(listener);  
  }  
 
  public void firePropertyChange(String propName, Object oldValue, Object newValue) {  
    listeners.firePropertyChange(propName, oldValue, newValue);  
  }  
 
  public void removePropertyChangeListener(PropertyChangeListener listener) {  
    listeners.removePropertyChangeListener(listener);  
  }  
} 

public class SimpleObserver implements PropertyChangeListener {  
    
  ....  
    
  @Override 
  public void propertyChange(PropertyChangeEvent evt) {  
    if(evt.getPropertyName().equals("Domain.name")){  
      //do some work  
    }  
  }  
    
} 

public class SimpleTest{  
  public static void main(String[] args) {  
    SimpleObserver observer = new SimpleObserver();  
    Domain domain = new Domain();  
    domain.addPropertyChangeListener(observer);  
    domain.setName("yangsq");  
    ......  
  }  
}