/**
* Returns all the Listeners to a topic.
*
* <p>The registry is NOT thread-safe, and so this can only be called from within the actor
* mailbox context.
*/
@Override
public final List<TActor> listenersFor(final Object topic) {
Preconditions.checkNotNull(topic, "topic cannot be null");
if (listeners != null) {
final List<Object> list = listeners.get(topic);
if (list != null) {
final List<TActor> result = new ArrayList<>(list.size());
boolean processQueue = false;
for (final Object obj : list) {
if (obj instanceof WeakReferenceWithTopic) {
final WeakReferenceWithTopic ref = (WeakReferenceWithTopic) obj;
final TActor actor = ref.get();
if (actor == null) {
processQueue = true;
} else {
result.add(actor);
}
} else {
final TActor actor = (TActor) obj;
result.add(actor);
}
}
if (processQueue) {
processWeakListenerQueue();
}
return result;
}
}
return Collections.emptyList();
}
/**
* Registers a listener actor.
*
* <p>The registry is NOT thread-safe, and so this can only be called from within the actor
* mailbox context.
*
* <p>The topic might be anything, but should be immutable. Remember that the registry is also
* used by base classes and derived classes. The topic cannot be null. The listener cannot be
* null. The listener must not already have been registered to this topic.
*/
@Override
public final void register(final Object topic, final TActor listener, final boolean weakRef) {
Preconditions.checkNotNull(topic, "topic cannot be null");
Preconditions.checkNotNull(listener, "listener cannot be null");
if (listeners == null) {
listeners = new HashMap<Object, List<Object>>();
}
List<Object> list = listeners.get(topic);
if (list == null) {
list = new ArrayList<Object>();
listeners.put(topic, list);
}
for (final Object obj : list) {
if (obj == listener) {
throw new IllegalStateException(
"listener " + listener + " already registered for topic " + topic);
} else if (obj instanceof WeakReferenceWithTopic) {
final WeakReferenceWithTopic ref = (WeakReferenceWithTopic) obj;
if (ref.get() == listener) {
throw new IllegalStateException(
"listener " + listener + " already registered for topic " + topic);
}
}
}
if (weakRef) {
if (refQueue == null) {
refQueue = new ReferenceQueue<Object>();
}
list.add(new WeakReferenceWithTopic(topic, listener, refQueue));
} else {
list.add(listener);
}
}
/**
* Unregisters a listener actor.
*
* <p>The registry is NOT thread-safe, and so this can only be called from within the actor
* mailbox context.
*
* @return true on success.
*/
@Override
public final boolean unregister(final Object topic, final TActor listener) {
Preconditions.checkNotNull(topic, "topic cannot be null");
Preconditions.checkNotNull(listener, "listener cannot be null");
if (listeners != null) {
final List<Object> list = listeners.get(topic);
if (list != null) {
final int size = list.size();
for (int i = 0; i < size; i++) {
final Object obj = list.get(i);
if (obj == listener) {
if (list.size() == 1) {
listeners.remove(topic);
} else {
list.remove(i);
}
return true;
} else if (obj instanceof WeakReferenceWithTopic) {
final WeakReferenceWithTopic ref = (WeakReferenceWithTopic) obj;
if (ref.get() == listener) {
if (list.size() == 1) {
listeners.remove(topic);
} else {
list.remove(i);
}
return true;
}
}
}
}
}
return false;
}
