static List<Listener> createListeners(Class<?> providerClass) {

        Object provider = ProviderFactory.newInstance("listener", providerClass);

        if (provider instanceof Listener) {
            return Collections.singletonList((Listener) provider);
        }

        return createListenerAdapters(provider);

    }
Creates all listeners represented by an instance of the given provider class.
<p>
If a provider class implements the simple Listener interface, that is the
only listener type that will be returned. Otherwise, a list of Listener
objects that adapt the legacy listener interfaces will be returned.

@param providerClass
     A class that represents a listener.

@return
     The list of listeners represented by the given provider class.
guacamole/src/main/java/org/apache/guacamole/extension/ListenerFactory.java