Class BeanProperty<S,V>

    BeanProperty.create("firstName");

Or to create a property representing the firstName property of an object's mother property:

    BeanProperty.create("mother.firstName");
 

An instance of BeanProperty is immutable and can be used with different source objects. When a PropertyStateListener is added to a BeanProperty for a given source object, the BeanProperty starts listening to all objects along the path (based on that source object) for change notification, and reflects any changes by notifying the listener associated with the property for that source object. So, in the second example above, if a PropertyStateListener is added to the property for an object Duke, the PropertyStateListener is notified when either Duke's mother changes (if the new mother's name is different), or Duke's mother's firstName changes.

It is very important that any bean properties addressed via a BeanProperty follow the Java Beans specification, including firing property change notification; otherwise, BeanProperty cannot respond to change. As some beans outside of your control may not follow the Java Beans specification, BeanProperty always checks the BeanAdapterFactory to see if a delegate provider has been registered to provide a delegate bean to take the place of an object for a given property. See the ext package level documentation for more details.

When there are no PropertyStateListeners installed on a BeanProperty for a given source, all Property methods act by traversing the entire path from the source to the end point, thereby always providing "live" information. On the contrary, when there are PropertyStateListeners installed, the beans along the path (including the final value) are cached, and only updated upon notification of change from a bean. Again, this makes it very important that any bean property that could change along the path fires property change notification.

Readability of a BeanProperty for a given source is defined as follows: A BeanProperty is readable for a given source if and only if a) each bean in the path, starting with the source, defines a Java Beans getter method for the the property to be read on it AND b) each bean in the path, starting with the source and ending with the bean on which we read the final property, is non-null. The final value being null does not affect the readability.

So, in the second example given earlier, the BeanProperty is readable for (@code Duke} when all of the following are true: Duke defines a Java Beans getter for mother, Duke's mother defines a Java Beans getter for firstName, Duke is non-null, Duke's mother is non-null. The BeanProperty is therefore unreadable when any of the following is true: Duke does not define a Java Beans getter for mother, Duke's mother does not define a Java Beans getter for firstName, Duke is null, Duke's mother is null.

Writeability of a BeanProperty for a given source is defined as follows: A BeanProperty is writeable for a given source if and only if a) each bean in the path, starting with the source and ending with the bean on which we set the final property, defines a Java Beans getter method for the property to be read on it AND b) the bean on which we set the final property defines a Java Beans setter for the property to be set on it AND c) each bean in the path, starting with the source and ending with the bean on which we set the final property, is non-null. The final value being null does not affect the writeability.

So, in the second example given earlier, the BeanProperty is writeable for Duke when all of the following are true: Duke defines a Java Beans getter for mother, Duke's mother defines a Java Beans setter for firstName, Duke is non-null, Duke's mother is non-null. The BeanProperty is therefore unreadable when any of the following is true: Duke does not define a Java Beans getter for mother, Duke's mother does not define a Java Beans setter for firstName, Duke is null, Duke's mother is null.

In addition to working on Java Beans properties, any object in the path can be an instance of Map. In this case, the Map's get method is used with the property name as the getter, and the Map's put method is used with the property name as the setter. BeanProperty can only respond to changes in Maps if they are instances of ObservableMap.

Some methods in this class document that they can throw PropertyResolutionException if an exception occurs while trying to resolve the path. The throwing of this exception represents an abnormal condition and if listeners are installed for the given source object, leaves the BeanProperty in an inconsistent state for that source object. A BeanProperty should not be used again for that same source object after such an exception without first removing all listeners associated with the BeanProperty for that source object.