Changed nomenclature from Broker to Registry.
diff --git a/net/api/src/main/java/org/onlab/onos/event/AbstractListenerRegistry.java b/net/api/src/main/java/org/onlab/onos/event/AbstractListenerRegistry.java
new file mode 100644
index 0000000..5e6011a
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/event/AbstractListenerRegistry.java
@@ -0,0 +1,64 @@
+package org.onlab.onos.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 AbstractListenerRegistry<E extends Event, L extends EventListener<E>>
+ implements EventSink<E> {
+
+ private final Logger log = getLogger(getClass());
+
+ private 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");
+ checkArgument(listeners.remove(listener), "Listener not registered");
+ }
+
+ @Override
+ public void process(E event) {
+ for (L listener : listeners) {
+ try {
+ listener.event(event);
+ } catch (Throwable error) {
+ reportProblem(event, error);
+ }
+ }
+ }
+
+ /**
+ * 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) {
+ log.warn("Exception encountered while processing event " + event, error);
+ }
+
+}