org.jdesktop.beans
Class AbstractBean

java.lang.Object
  org.jdesktop.beans.AbstractBean

Direct Known Subclasses:

AbstractFilter, AbstractPainter, AbstractSerializableBean, JXGraph.Plot, LoginService, UserNameStore

public abstract class AbstractBean
extends java.lang.Object

A convenience class from which to extend all non-visual AbstractBeans. It manages the PropertyChange notification system, making it relatively trivial to add support for property change events in getters/setters.

A non-visual java bean is a Java class that conforms to the AbstractBean patterns to allow visual manipulation of the bean's properties and event handlers at design-time.

Here is a simple example bean that contains one property, foo, and the proper pattern for implementing property change notification:

 public class ABean extends AbstractBean {
     private String foo;
 
     public void setFoo(String newFoo) {
         String old = getFoo();
         this.foo = newFoo;
         firePropertyChange("foo", old, getFoo());
     }
 
     public String getFoo() {
         return foo;
     }
 }
 

You will notice that "getFoo()" is used in the setFoo method rather than accessing "foo" directly for the gets. This is done intentionally so that if a subclass overrides getFoo() to return, for instance, a constant value the property change notification system will continue to work properly.

The firePropertyChange method takes into account the old value and the new value. Only if the two differ will it fire a property change event. So you can be assured from the above code fragment that a property change event will only occur if old is indeed different from getFoo()

AbstractBean also supports vetoable PropertyChangeEvent events. These events are similar to PropertyChange events, except a special exception can be used to veto changing the property. For example, perhaps the property is changing from "fred" to "red", but a listener deems that "red" is unexceptable. In this case, the listener can fire a veto exception and the property must remain "fred". For example:

  public class ABean extends AbstractBean {
    private String foo;
    
    public void setFoo(String newFoo) throws PropertyVetoException {
      String old = getFoo();
      this.foo = newFoo;
      fireVetoableChange("foo", old, getFoo());
    }
    public String getFoo() {
      return foo;
    }
  }
 
  public class Tester {
    public static void main(String... args) {
      try {
        ABean a = new ABean();
        a.setFoo("fred");
        a.addVetoableChangeListener(new VetoableChangeListener() {
          public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
            if ("red".equals(evt.getNewValue()) {
              throw new PropertyVetoException("Cannot be red!", evt);
            }
          }
        }
        a.setFoo("red");
      } catch (Exception e) {
        e.printStackTrace(); // this will be executed
      }
    }
  }
 

AbstractBean is not Serializable. Special care must be taken when creating Serializable subclasses, as the Serializable listeners will not be saved. Subclasses will need to manually save the serializable listeners. The AbstractSerializableBean is Serializable and already handles the listeners correctly. If possible, it is recommended that Serializable beans should extend AbstractSerializableBean. If it is not possible, the AbstractSerializableBean bean implementation provides details on how to correctly serialize an AbstractBean subclass.

Author:

rbair

See Also:

AbstractSerializableBean

Method Summary

void	addPropertyChangeListener(java.beans.PropertyChangeListener listener) Add a PropertyChangeListener to the listener list.
void	addPropertyChangeListener(java.lang.String propertyName, java.beans.PropertyChangeListener listener) Add a PropertyChangeListener for a specific property.
void	addVetoableChangeListener(java.lang.String propertyName, java.beans.VetoableChangeListener listener) Add a VetoableChangeListener for a specific property.
void	addVetoableChangeListener(java.beans.VetoableChangeListener listener) Add a VetoableListener to the listener list.
java.lang.Object	clone()
java.beans.PropertyChangeListener[]	getPropertyChangeListeners() Returns an array of all the listeners that were added to the PropertyChangeSupport object with addPropertyChangeListener().
java.beans.PropertyChangeListener[]	getPropertyChangeListeners(java.lang.String propertyName) Returns an array of all the listeners which have been associated with the named property.
java.beans.VetoableChangeListener[]	getVetoableChangeListeners() Returns the list of VetoableChangeListeners.
java.beans.VetoableChangeListener[]	getVetoableChangeListeners(java.lang.String propertyName) Returns an array of all the listeners which have been associated with the named property.
void	removePropertyChangeListener(java.beans.PropertyChangeListener listener) Remove a PropertyChangeListener from the listener list.
void	removePropertyChangeListener(java.lang.String propertyName, java.beans.PropertyChangeListener listener) Remove a PropertyChangeListener for a specific property.
void	removeVetoableChangeListener(java.lang.String propertyName, java.beans.VetoableChangeListener listener) Remove a VetoableChangeListener for a specific property.
void	removeVetoableChangeListener(java.beans.VetoableChangeListener listener) Remove a VetoableChangeListener from the listener list.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

addPropertyChangeListener

public final void addPropertyChangeListener(java.beans.PropertyChangeListener listener)

Add a PropertyChangeListener to the listener list. The listener is registered for all properties. The same listener object may be added more than once, and will be called as many times as it is added. If listener is null, no exception is thrown and no action is taken.

Parameters:

listener - The PropertyChangeListener to be added

removePropertyChangeListener

public final void removePropertyChangeListener(java.beans.PropertyChangeListener listener)

Remove a PropertyChangeListener from the listener list. This removes a PropertyChangeListener that was registered for all properties. If listener was added more than once to the same event source, it will be notified one less time after being removed. If listener is null, or was never added, no exception is thrown and no action is taken.

Parameters:

listener - The PropertyChangeListener to be removed

getPropertyChangeListeners

public final java.beans.PropertyChangeListener[] getPropertyChangeListeners()

Returns an array of all the listeners that were added to the PropertyChangeSupport object with addPropertyChangeListener().

If some listeners have been added with a named property, then the returned array will be a mixture of PropertyChangeListeners and PropertyChangeListenerProxys. If the calling method is interested in distinguishing the listeners then it must test each element to see if it's a PropertyChangeListenerProxy, perform the cast, and examine the parameter.

 PropertyChangeListener[] listeners = bean.getPropertyChangeListeners();
 for (int i = 0; i < listeners.length; i++) {
     if (listeners[i] instanceof PropertyChangeListenerProxy) {
     PropertyChangeListenerProxy proxy = 
                    (PropertyChangeListenerProxy)listeners[i];
     if (proxy.getPropertyName().equals("foo")) {
       // proxy is a PropertyChangeListener which was associated
       // with the property named "foo"
     }
   }
 }

Returns:

all of the PropertyChangeListeners added or an empty array if no listeners have been added

See Also:

PropertyChangeListenerProxy

addPropertyChangeListener

public final void addPropertyChangeListener(java.lang.String propertyName,
                                            java.beans.PropertyChangeListener listener)

Add a PropertyChangeListener for a specific property. The listener will be invoked only when a call on firePropertyChange names that specific property. The same listener object may be added more than once. For each property, the listener will be invoked the number of times it was added for that property. If propertyName or listener is null, no exception is thrown and no action is taken.

Parameters:

propertyName - The name of the property to listen on.

listener - The PropertyChangeListener to be added

removePropertyChangeListener

public final void removePropertyChangeListener(java.lang.String propertyName,
                                               java.beans.PropertyChangeListener listener)

Remove a PropertyChangeListener for a specific property. If listener was added more than once to the same event source for the specified property, it will be notified one less time after being removed. If propertyName is null, no exception is thrown and no action is taken. If listener is null, or was never added for the specified property, no exception is thrown and no action is taken.

Parameters:

propertyName - The name of the property that was listened on.

listener - The PropertyChangeListener to be removed

getPropertyChangeListeners

public final java.beans.PropertyChangeListener[] getPropertyChangeListeners(java.lang.String propertyName)

Returns an array of all the listeners which have been associated with the named property.

Parameters:

propertyName - The name of the property being listened to

Returns:

all of the PropertyChangeListeners associated with the named property. If no such listeners have been added, or if propertyName is null, an empty array is returned.

addVetoableChangeListener

public final void addVetoableChangeListener(java.beans.VetoableChangeListener listener)

Add a VetoableListener to the listener list. The listener is registered for all properties. The same listener object may be added more than once, and will be called as many times as it is added. If listener is null, no exception is thrown and no action is taken.

Parameters:

listener - The VetoableChangeListener to be added

removeVetoableChangeListener

public final void removeVetoableChangeListener(java.beans.VetoableChangeListener listener)

Remove a VetoableChangeListener from the listener list. This removes a VetoableChangeListener that was registered for all properties. If listener was added more than once to the same event source, it will be notified one less time after being removed. If listener is null, or was never added, no exception is thrown and no action is taken.

Parameters:

listener - The VetoableChangeListener to be removed

getVetoableChangeListeners

public final java.beans.VetoableChangeListener[] getVetoableChangeListeners()

Returns the list of VetoableChangeListeners. If named vetoable change listeners were added, then VetoableChangeListenerProxy wrappers will returned

Returns:

List of VetoableChangeListeners and VetoableChangeListenerProxys if named property change listeners were added.

addVetoableChangeListener

public final void addVetoableChangeListener(java.lang.String propertyName,
                                            java.beans.VetoableChangeListener listener)

Add a VetoableChangeListener for a specific property. The listener will be invoked only when a call on fireVetoableChange names that specific property. The same listener object may be added more than once. For each property, the listener will be invoked the number of times it was added for that property. If propertyName or listener is null, no exception is thrown and no action is taken.

Parameters:

propertyName - The name of the property to listen on.

listener - The VetoableChangeListener to be added

removeVetoableChangeListener

public final void removeVetoableChangeListener(java.lang.String propertyName,
                                               java.beans.VetoableChangeListener listener)

Remove a VetoableChangeListener for a specific property. If listener was added more than once to the same event source for the specified property, it will be notified one less time after being removed. If propertyName is null, no exception is thrown and no action is taken. If listener is null, or was never added for the specified property, no exception is thrown and no action is taken.

Parameters:

propertyName - The name of the property that was listened on.

listener - The VetoableChangeListener to be removed

getVetoableChangeListeners

public final java.beans.VetoableChangeListener[] getVetoableChangeListeners(java.lang.String propertyName)

Returns an array of all the listeners which have been associated with the named property.

Parameters:

propertyName - The name of the property being listened to

Returns:

all the VetoableChangeListeners associated with the named property. If no such listeners have been added, or if propertyName is null, an empty array is returned.

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Overrides:

clone in class java.lang.Object

Throws:

java.lang.CloneNotSupportedException