Renamed AbstractListenerRegistry to ListenerRegistry (since it is not abstract).
- added checkForNonRegistrant() predicate and augmented unit tests.
Change-Id: I7ecc618f01fdc4cead6f143a1e5e0ddd03268efc
diff --git a/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java b/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java
new file mode 100644
index 0000000..4164441
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java
@@ -0,0 +1,115 @@
+/*
+ * Copyright 2014 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.event;
+
+import org.slf4j.Logger;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Base implementation of an event sink and a registry capable of tracking
+ * listeners and dispatching events to them as part of event sink processing.
+ */
+public class ListenerRegistry<E extends Event, L extends EventListener<E>>
+ implements EventSink<E> {
+
+ private final Logger log = getLogger(getClass());
+
+ private volatile boolean shutdown = false;
+
+ /**
+ * Set of listeners that have registered.
+ */
+ protected final Set<L> listeners = new CopyOnWriteArraySet<>();
+
+
+ /**
+ * Adds the specified listener.
+ *
+ * @param listener listener to be added
+ */
+ public void addListener(L listener) {
+ checkNotNull(listener, "Listener cannot be null");
+ listeners.add(listener);
+ }
+
+ /**
+ * Removes the specified listener.
+ *
+ * @param listener listener to be removed
+ */
+ public void removeListener(L listener) {
+ checkNotNull(listener, "Listener cannot be null");
+ if (checkForNonRegistrant()) {
+ checkArgument(listeners.remove(listener), "Listener not registered");
+ }
+ }
+
+ @Override
+ public void process(E event) {
+ for (L listener : listeners) {
+ try {
+ listener.event(event);
+ } catch (Exception error) {
+ reportProblem(event, error);
+ }
+ }
+ }
+
+ /**
+ * Predicate indicating whether we should throw an exception if the
+ * argument to {@link #removeListener} is not in the current set of
+ * listeners.
+ * <p>
+ * This default implementation returns <code>true</code>.
+ *
+ * @return true if non-listed listeners should cause exception on remove
+ */
+ protected boolean checkForNonRegistrant() {
+ return true;
+ }
+
+ /**
+ * Reports a problem encountered while processing an event.
+ *
+ * @param event event being processed
+ * @param error error encountered while processing
+ */
+ protected void reportProblem(E event, Throwable error) {
+ if (!shutdown) {
+ log.warn("Exception encountered while processing event " + event, error);
+ }
+ }
+
+ /**
+ * Prepares the registry for normal operation.
+ */
+ public void activate() {
+ shutdown = false;
+ }
+
+ /**
+ * Prepares the registry for shutdown.
+ */
+ public void deactivate() {
+ shutdown = true;
+ }
+}