tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 1 | package org.onlab.onos.event; |
| 2 | |
| 3 | import org.slf4j.Logger; |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 4 | |
| 5 | import java.util.Set; |
| 6 | import java.util.concurrent.CopyOnWriteArraySet; |
| 7 | |
| 8 | import static com.google.common.base.Preconditions.checkArgument; |
| 9 | import static com.google.common.base.Preconditions.checkNotNull; |
tom | 5f38b3a | 2014-08-27 23:50:54 -0700 | [diff] [blame] | 10 | import static org.slf4j.LoggerFactory.getLogger; |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 11 | |
| 12 | /** |
tom | 96dfcab | 2014-08-28 09:26:03 -0700 | [diff] [blame] | 13 | * Base implementation of an event sink and a registry capable of tracking |
| 14 | * listeners and dispatching events to them as part of event sink processing. |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 15 | */ |
tom | 96dfcab | 2014-08-28 09:26:03 -0700 | [diff] [blame] | 16 | public class AbstractListenerRegistry<E extends Event, L extends EventListener<E>> |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 17 | implements EventSink<E> { |
| 18 | |
tom | 5f38b3a | 2014-08-27 23:50:54 -0700 | [diff] [blame] | 19 | private final Logger log = getLogger(getClass()); |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 20 | |
| 21 | private final Set<L> listeners = new CopyOnWriteArraySet<>(); |
Thomas Vachuska | 7d693f5 | 2014-10-21 19:17:57 -0700 | [diff] [blame] | 22 | private volatile boolean shutdown = false; |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 23 | |
| 24 | /** |
| 25 | * Adds the specified listener. |
| 26 | * |
| 27 | * @param listener listener to be added |
| 28 | */ |
| 29 | public void addListener(L listener) { |
| 30 | checkNotNull(listener, "Listener cannot be null"); |
| 31 | listeners.add(listener); |
| 32 | } |
| 33 | |
| 34 | /** |
| 35 | * Removes the specified listener. |
| 36 | * |
| 37 | * @param listener listener to be removed |
| 38 | */ |
| 39 | public void removeListener(L listener) { |
| 40 | checkNotNull(listener, "Listener cannot be null"); |
| 41 | checkArgument(listeners.remove(listener), "Listener not registered"); |
| 42 | } |
| 43 | |
| 44 | @Override |
| 45 | public void process(E event) { |
| 46 | for (L listener : listeners) { |
| 47 | try { |
| 48 | listener.event(event); |
tom | 19bf421 | 2014-08-29 13:08:29 -0700 | [diff] [blame] | 49 | } catch (Exception error) { |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 50 | reportProblem(event, error); |
| 51 | } |
| 52 | } |
| 53 | } |
| 54 | |
tom | b36046e | 2014-08-27 00:22:24 -0700 | [diff] [blame] | 55 | /** |
| 56 | * Reports a problem encountered while processing an event. |
| 57 | * |
| 58 | * @param event event being processed |
| 59 | * @param error error encountered while processing |
| 60 | */ |
| 61 | protected void reportProblem(E event, Throwable error) { |
Thomas Vachuska | 7d693f5 | 2014-10-21 19:17:57 -0700 | [diff] [blame] | 62 | if (!shutdown) { |
| 63 | log.warn("Exception encountered while processing event " + event, error); |
| 64 | } |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 65 | } |
| 66 | |
Thomas Vachuska | 7d693f5 | 2014-10-21 19:17:57 -0700 | [diff] [blame] | 67 | /** |
| 68 | * Prepares the registry for normal operation. |
| 69 | */ |
| 70 | public void activate() { |
| 71 | shutdown = false; |
| 72 | } |
| 73 | |
| 74 | /** |
| 75 | * Prepares the registry for shutdown. |
| 76 | */ |
| 77 | public void deactivate() { |
| 78 | shutdown = true; |
| 79 | } |
| 80 | |
| 81 | |
tom | d735672 | 2014-08-26 01:07:39 -0700 | [diff] [blame] | 82 | } |