Java Doc for BeanAdapter.java in  » Swing-Library » jgoodies-data-binding » com » jgoodies » binding » beans » Java Source Code / Java DocumentationJava Source Code and Java Documentation

ValueModels can be created for a property name using BeanAdapter.getValueModel(String) or for a triple of (property name, getter name, setter name) using BeanAdapter.getValueModel(String,String,String) . If you just specify the property name, the adapter uses the standard Java Bean introspection to lookup the available properties and how to read and write the property value. In case of custom readers and writers you may specify a custom BeanInfo class, or as a shortcut use the method that accepts the optional getter and setter name. If these are specified, introspection will be bypassed and a PropertyDescriptor will be created for the given property name, getter and setter name. Note: For each property name subsequent calls to these methods must use the same getter and setter names. Attempts to violate this constraint are rejected with an IllegalArgumentException.

Property values for a given property name can be read using BeanAdapter.getValue(String) . To set a value for a for a property name invoke BeanAdapter.setValue(String,Object) .

Optionally the BeanAdapter can observe changes in bound properties as described in section 7.4 of the Bean specification. The bean then must provide support for listening on properties as described in section 7.4 of this specification. You can enable this feature by setting the constructor parameter observeChanges to true. If the adapter observes changes, the ValueModels returned by #getValueModel will fire value change events, i.e. PropertyChangeEvents for the property "value". Even if you ignore property changes, you can access the adapted property value via #getValue(). It's just that you won't be notified about changes.

In addition you can observe the bean's bound properties by registering PropertyChangeListeners with the bean using #addBeanPropertyChangeListener. These listeners will be removed from the old bean before the bean changes and will be re-added after the new bean has been set. Therefore these listeners will be notified about changes only if the current bean changes a property. They won't be notified if the bean changes - and in turn the property value. If you want to observes property changes caused by bean changes too, register with the adapting ValueModel as returned by #getValueModel(String).

The BeanAdapter provides two access styles to the target bean that holds the adapted property: you can specify a bean directly, or you can use a bean channel to access the bean indirectly. In the latter case you specify a ValueModel that holds the bean that in turn holds the adapted properties.

If the adapted bean is null the BeanAdapter can neither read nor set a value. In this case #getValue returns null and #setValue will silently ignore the new value.

This adapter throws three PropertyChangeEvents if the bean changes: beforeBean, bean and afterBean. This is useful when sharing a bean channel and you must perform an operation before or after other listeners handle a bean change. Since you cannot rely on the order listeners will be notified, only the beforeBean and afterBean events are guaranteed to be fired before and after the bean change is fired. Note that #getBean() returns the new bean before any of these three PropertyChangeEvents is fired. Therefore listeners that handle these events must use the event's old and new value to determine the old and new bean. The order of events fired during a bean change is:

1. this adapter's bean channel fires a value change,
2. this adapter fires a beforeBean change,
3. this adapter fires the bean change,
4. this adapter fires an afterBean change.

Note: BeanAdapters that observe changes have a PropertyChangeListener registered with the target bean. Hence, a bean has a reference to any BeanAdapter that observes it. To avoid memory leaks it is recommended to remove this listener if the bean lives much longer than the BeanAdapter, enabling the garbage collector to remove the adapter. To do so, you can call setBean(null) or set the bean channel's value to null. As an alternative you can use event listener lists in your beans that implement references with WeakReference.

Setting the bean to null has side-effects, for example the adapter fires a change event for the bound property bean and other properties. And the value of ValueModel's vended by this adapter may change. However, typically this is fine and setting the bean to null is the first choice for removing the reference from the bean to the adapter. Another way to clear the reference from the target bean is to call #release. It has no side-effects, but the adapter must not be used anymore once #release has been called.

Constraints: If property changes shall be observed, the bean class must support bound properties, i. e. it must provide the following pair of methods for registration of multicast property change event listeners:

 public void addPropertyChangeListener(PropertyChangeListener x);
 public void removePropertyChangeListener(PropertyChangeListener x);
 

Basic Examples:

 // Direct access, ignores changes
 Address address = new Address()
 BeanAdapter adapter = new BeanAdapter(address);
 adapter.setValue("street", "Broadway");
 System.out.println(address.getStreet());        // Prints "Broadway"
 address.setStreet("Franz-Josef-Str.");
 System.out.println(adapter.getValue("street")); // Prints "Franz-Josef-Str."
 //Direct access, observes changes
 BeanAdapter adapter = new BeanAdapter(address, true);
 // Indirect access, ignores changes
 ValueHolder addressHolder = new ValueHolder(address1);
 BeanAdapter adapter = new BeanAdapter(addressHolder);
 adapter.setValue("street", "Broadway");         // Sets the street in address1
 System.out.println(address1.getStreet());       // Prints "Broadway"
 adapter.setBean(address2);
 adapter.setValue("street", "Robert-Koch-Str."); // Sets the street in address2
 System.out.println(address2.getStreet());       // Prints "Robert-Koch-Str."
 // Indirect access, observes changes
 ValueHolder addressHolder = new ValueHolder();
 BeanAdapter adapter = new BeanAdapter(addressHolder, true);
 addressHolder.setValue(address1);
 address1.setStreet("Broadway");
 System.out.println(adapter.getValue("street")); // Prints "Broadway"
 // Access through ValueModels
 Address address = new Address();
 BeanAdapter adapter = new BeanAdapter(address);
 ValueModel streetModel = adapter.getValueModel("street");
 ValueModel cityModel   = adapter.getValueModel("city");
 streetModel.setValue("Broadway");
 System.out.println(address.getStreet());        // Prints "Broadway"
 address.setCity("Hamburg");
 System.out.println(cityModel.getValue());       // Prints "Hamburg"
 

 Country country = new Country();
 country.setName("Germany");
 country.setEuMember(true);
 BeanAdapter countryAdapter = new BeanAdapter(country, true);
 JTextField nameField = new JTextField();
 nameField.setDocument(new DocumentAdapter(
 countryAdapter.getValueModel("name")));
 JCheckBox euMemberBox = new JCheckBox("Is EU Member");
 euMemberBox.setModel(new ToggleButtonAdapter(
 countryAdapter.getValueModel("euMember")));
 // Using factory methods
 JTextField nameField   = Factory.createTextField(country, "name");
 JCheckBox  euMemberBox = Factory.createCheckBox (country, "euMember");
 euMemberBox.setText("Is EU Member");
 

As of version 1.3 this class is no longer marked as final, but lacks the documentation for subclass constraints. I plan to introduce an interface that shall describe the semantics required by the PresentationModel class. Until then, this BeanAdapter implementation describes the semantics and all constraints.

TODO: Improve the class comment and focus on the main features.

TODO: Consider adding a feature to ensure that update notifications are performed in the event dispatch thread. In case the adapted bean is changed in a thread other than the event dispatch thread, such a feature would help complying with Swing's single thread rule. The feature could be implemented by an extended PropertyChangeSupport.

TODO: I plan to improve the support for adapting beans that do not fire PropertyChangeEvents. This affects the classes PropertyAdapter, BeanAdapter, and PresentationModel. Basically the PropertyAdapter and the BeanAdapter's internal SimplePropertyAdapter's shall be able to optionally self-fire a PropertyChangeEvent in case the bean does not. There are several downsides with self-firing events compared to bound bean properties. See Issue 49 for more information about the downsides.

The observeChanges constructor parameter shall be replaced by a more fine-grained choice to not observe (former observeChanges=false), to observe bound properties (former observeChanges=true), and a new setting for self-firing PropertyChangeEvents if a value is set. The latter case may be further splitted up to specify how the self-fired PropertyChangeEvent is created:

1. oldValue=null, newValue=null
2. oldValue=null, newValue=the value set
3. oldValue=value read before the set, newValue=the value set
4. oldValue=value read before the set, newValue=value read after the set

Installs a default bean channel that checks the identity not equity to ensure that listeners are reregistered properly if the old and new bean are equal but not the same.

Installs a default bean channel that checks the identity not equity to ensure that listeners are reregistered properly if the old and new bean are equal but not the same.
Parameters:
  bean - the bean that owns the properties to adapt
Parameters:
  observeChanges - true to observe changes of boundor constrained properties, false to ignore changes
throws:
  PropertyUnboundException - if observeChangesis true but the property is unbound, i.

It is strongly recommended that the bean channel checks the identity not equity.

It is strongly recommended that the bean channel checks the identity not equity.

This operation is supported only for readable bean properties.

BeanAdapters that observe changes have a PropertyChangeListener registered with the target bean.

Installs a default bean channel that checks the identity not equity to ensure that listeners are reregistered properly if the old and new bean are equal but not the same.
Parameters:
  bean - the bean that owns the properties to adapt

Installs a default bean channel that checks the identity not equity to ensure that listeners are reregistered properly if the old and new bean are equal but not the same.
Parameters:
  bean - the bean that owns the properties to adapt
Parameters:
  observeChanges - true to observe changes of boundor constrained properties, false to ignore changes
throws:
  PropertyUnboundException - if observeChangesis true but the property is unbound, i. e. the beandoes not provide a pair of methods to register a multicastPropertyChangeListener

It is strongly recommended that the bean channel checks the identity not equity. This ensures that listeners are reregistered properly if the old and new bean are equal but not the same.
Parameters:
  beanChannel - the ValueModel that holds the bean

It is strongly recommended that the bean channel checks the identity not equity. This ensures that listeners are reregistered properly if the old and new bean are equal but not the same.
Parameters:
  beanChannel - the ValueModel that holds the bean
Parameters:
  observeChanges - true to observe changes of boundor constrained properties, false to ignore changes
throws:
  IllegalArgumentException - if the beanChannel is a ValueHolderthat has the identityCheck feature disabled
throws:
  PropertyUnboundException - if observeChangesis true but the property is unbound, i. e. the beandoes not provide a pair of methods to register a multicastPropertyChangeListener

The listener will be notified if and only if this BeanAdapter's current bean changes a property. It'll not be notified if the bean changes.

If listener is null, no exception is thrown and no action is performed.
Parameters:
  listener - the PropertyChangeListener to be added
See Also:   BeanAdapter.removeBeanPropertyChangeListener(PropertyChangeListener)
See Also:   BeanAdapter.removeBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.addBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.getBeanPropertyChangeListeners()

The listener will be notified if and only if this BeanAdapter's current bean changes the specified property. It'll not be notified if the bean changes. If you want to observe property changes and bean changes, you may observe the ValueModel that adapts this property - as returned by #getValueModel(String).

Note that if the bean is inheriting a bound property, then no event will be fired in response to a change in the inherited property.

If listener is null, no exception is thrown and no action is performed.
Parameters:
  propertyName - one of the property names listed above
Parameters:
  listener - the PropertyChangeListener to be added
See Also:   BeanAdapter.removeBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.addBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.getBeanPropertyChangeListeners(String)

This operation is supported only for readable bean properties.
Parameters:
  propertyName - the name of the property to be read the value of the adapted bean property, null if the bean is null
throws:
  NullPointerException - if propertyName is null
throws:
  UnsupportedOperationException - if the property is write-only
throws:
  PropertyNotFoundException - if the property could not be found
throws:
  PropertyAccessException - if the value could not be read

Subsequent calls to this method with the same property name return the same ValueModel.

To prevent potential runtime errors this method eagerly looks up the associated PropertyDescriptor if the target bean is not null.

For each property name all calls to this method and to #getValueModel(String, String, String) must use the same getter and setter names. Attempts to violate this constraint will be rejected with an IllegalArgumentException. Especially once you've called this method you must not call #getValueModel(String, String, String) with a non-null getter or setter name. And vice versa, once you've called the latter method with a non-null getter or setter name, you must not call this method.

This method uses a return type of AbstractValueModel, not a ValueModel. This makes BeanAdapter.setVetoableValue(String,Object) visible. It also makes the AbstractValueModel convenience type converters available, which can significantly shrink the source code necessary to read and write values from/to these models.
Parameters:
  propertyName - the name of the property to adapt a ValueModel that adapts the property with the specified name
throws:
  NullPointerException - if propertyName is null
throws:
  PropertyNotFoundException - if the property could not be found
throws:
  IllegalArgumentException - if #getValueModel(String, String, String) has beencalled before with the same property name and a non-null getteror setter name

Subsequent calls to this method with the same parameters will return the same ValueModel.

To prevent potential runtime errors this method eagerly looks up the associated PropertyDescriptor if the target bean is not null.

For each property name all calls to this method and to #getValueModel(String) must use the same getter and setter names. Attempts to violate this constraint will be rejected with an IllegalArgumentException. Especially once you've called this method with a non-null getter or setter name, you must not call #getValueModel(String). And vice versa, once you've called the latter method you must not call this method with a non-null getter or setter name.

This method uses a return type of AbstractValueModel, not a ValueModel. This makes BeanAdapter.setVetoableValue(String,Object) visible. It also makes the AbstractValueModel convenience type converters available, which can significantly shrink the source code necessary to read and write values from/to these models.
Parameters:
  propertyName - the name of the property to adapt
Parameters:
  getterName - the name of the method that reads the value
Parameters:
  setterName - the name of the method that sets the value a ValueModel that adapts the property with the specified name
throws:
  NullPointerException - if propertyName is null
throws:
  PropertyNotFoundException - if the property could not be found
throws:
  IllegalArgumentException - if this method has been called beforewith the same property name and different getter or setter names

BeanAdapters that observe changes have a PropertyChangeListener registered with the target bean. Hence, a bean has a reference to all BeanAdapters that observe it. To avoid memory leaks it is recommended to remove this listener if the bean lives much longer than the BeanAdapter, enabling the garbage collector to remove the adapter. To do so, you can call setBean(null) or set the bean channel's value to null. As an alternative you can use event listener lists in your beans that implement references with WeakReference.

Setting the bean to null has side-effects, for example the adapter fires a change event for the bound property bean and other properties. And the value of ValueModel's vended by this adapter may change. However, typically this is fine and setting the bean to null is the first choice for removing the reference from the bean to the adapter. Another way to clear the reference from the target bean is to call #release. It has no side-effects, but the adapter must not be used anymore once #release has been called.
See Also:   BeanAdapter.setBean(Object)
See Also:   java.lang.ref.WeakReference

If listener is null, no exception is thrown and no action is performed.
Parameters:
  listener - the PropertyChangeListener to be removed
See Also:   BeanAdapter.addBeanPropertyChangeListener(PropertyChangeListener)
See Also:   BeanAdapter.addBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.removeBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.getBeanPropertyChangeListeners()

If listener is null, no exception is thrown and no action is performed.
Parameters:
  propertyName - a valid property name
Parameters:
  listener - the PropertyChangeListener to be removed
See Also:   BeanAdapter.addBeanPropertyChangeListener(String,PropertyChangeListener)
See Also:   BeanAdapter.removeBeanPropertyChangeListener(PropertyChangeListener)
See Also:   BeanAdapter.getBeanPropertyChangeListeners(String)

Resets the changed state to false.

If this adapter observes bean changes, the bean change handler will be removed from the former bean and will be added to the new bean. Hence, if the new bean is null, this adapter has no listener registered with a bean. And so, setBean(null) can be used as a clean release method that allows to use this adapter later again.
Parameters:
  newBean - the new holder of the adapted properties
See Also:   BeanAdapter.getBean()
See Also:   BeanAdapter.isChanged()
See Also:   BeanAdapter.resetChanged()
See Also:   BeanAdapter.release()

Notifies the associated value change listeners if the bean reports a property change. Note that a bean may suppress PropertyChangeEvents if the old and new value are the same, or if the old and new value are equal.

This operation is supported only for writable bean properties.
Parameters:
  propertyName - the name of the property to set
Parameters:
  newValue - the value to set
throws:
  NullPointerException - if propertyName is null
throws:
  UnsupportedOperationException - if the property is read-only
throws:
  PropertyNotFoundException - if the property could not be found
throws:
  PropertyAccessException - if the new value could not be set

Notifies the associated value change listeners if the bean reports a property change. Note that a bean may suppress PropertyChangeEvents if the old and new value are the same, or if the old and new value are equal.

This operation is supported only for writable bean properties.
Parameters:
  propertyName - the name of the property to set
Parameters:
  newValue - the value to set
throws:
  NullPointerException - if propertyName is null
throws:
  UnsupportedOperationException - if the property is read-only
throws:
  PropertyNotFoundException - if the property could not be found
throws:
  PropertyAccessException - if the new value could not be set
throws:
  PropertyVetoException - if the bean setterthrows a PropertyVetoException
since:
   1.1