| 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 (Exception 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); |
| } |
| |
| } |