Re: Binding to a POJO
Tom Anderson <twic@urchin.earth.li> writes:
On Sat, 5 Mar 2011, Jim Janney wrote:
Tom Anderson <twic@urchin.earth.li> writes:
Okay, how about:
public class PropertyChangeUtils {
private static final PropertyChangeSupport support; // initialise this somehow
public static <T> T change(String propertyName, T oldValue, T newValue) {
support.firePropertyChange(propertyName, oldValue, newValue);
return newValue;
}
}
import static PropertyChangeUtils.change;
private String foo;
public void setFoo(Object foo) {
this.foo = change("foo", this.foo, foo);
}
The code in the setter is fractionally (well, ~25%) more complicated
than with your version, but there's no reflection, and you have static
type safety.
It does fire the property change event before actually changing the
property, though; i don't know enough about Swing to know if that
would be a problem.
That breaks what I see as the implicit contract for property change
events: a listener receiving a change event can reasonably expect to
call the object's getter and see the new value.
Do the listeners get notified synchronously inside the
firePropertyChange call, or does that queue up an event to be handled
by the EDT once the current event is over or something like that? If
the former, then yes, my idea is pretty poor.
The implementation in PropertyChangeSupport is completely synchronous;
it just keeps a list of listeners and calls propertyChange() on each of
them. It's likely that the listeners installed by the JGoodies binding
framework then respond by queueing up events for the EDT, but they're
not required to do that.
More importantly, each object has its own set of listeners, and so
needs its own instance of PropertyChangeSupport to keep track of
them: you can't share a PropertyChangeSupport instance between
objects.
Whoops. In that case, put the support variable in the bean (via a base
class, perhaps), and pass it to the helper function as a parameter.
Yeah, that should work.
--
Jim Janney
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