java: PropertyChangeSupport for Map or EnumMap?

Question

Is there a version of either java.beans.PropertyChangeSupport or com.jgoodies.binding.beans.ExtendedPropertyChangeSupport which is helpful for supporting change listeners along the lines of a Map or EnumMap? (a key-value store with known limited keys and change listeners for all the values in the map)

I don't really need beans-type access, I have a number of different statistics sort of like:

interface hasName() {
    public String getName();
}

enum StatisticType implements hasName {
    MILES_DRIVEN, BURGERS_SERVED, CUSTOMERS_HELPED, BIRDS_WATCHED;
    @Override public String getName() { return name(); }
}

where I want to publish an interface like:

interface KeyValueStore<K extends hasName,V>
{
    void setValue(K key, V value);
    V getValue(K key);

    void addPropertyChangeListener(PropertyChangeListener listener);
    void removePropertyChangeListener(PropertyChangeListener listener);        
    /*
     * when setValue() is called, this should send PropertyChangeEvents
     * to all listeners, with the property name of K.getName()
     */
}

so I could use a KeyValueStore<StatisticType, Integer> in my application.

Is there any convenient way to do this? My head is spinning around in circles and it's sapping my energy trying to reinvent the wheel on this stuff.

Answer 1

Unless there is a pressing reason not to, I would extend Map and use put and get instead of setValue and getValue .

I have an interface I often use:

public interface PropertyChangeNotification {
    void addPropertyChangeListener(String property, PropertyChangeListener listener);
    void removePropertyChangeListener(String property, PropertyChangeListener listener);
    void addPropertyChangeListener(PropertyChangeListener listener);
    void removePropertyChangeListener(PropertyChangeListener listener);
}

With that, your interface becomes:

interface KeyValueStore<K extends hasName,V>
    extends Map<K,V>, PropertyChangeNotification
{
}

Then your implementation winds up looking something like this:

public class MyKeyStore<K extends hasName, V>
    extends HashMap<K,V>
    implements KeyValueStore<K,V>
{
    private PropertyChangeSupport changer = new PropertyChangeSupport(this);

    public void put(K key, V value)
    {
        V old = get(K);
        super.put(key,value);
        changer.firePropertyChange(key.getName(), value, old);
    }
}

Not shown are the 4 methods for the PropertyChangeNotification functionality that simply delegate to changer .