1 /*
2 * ModeShape (http://www.modeshape.org)
3 * See the COPYRIGHT.txt file distributed with this work for information
4 * regarding copyright ownership. Some portions may be licensed
5 * to Red Hat, Inc. under one or more contributor license agreements.
6 * See the AUTHORS.txt file in the distribution for a full listing of
7 * individual contributors.
8 *
9 * ModeShape is free software. Unless otherwise indicated, all code in ModeShape
10 * is licensed to you under the terms of the GNU Lesser General Public License as
11 * published by the Free Software Foundation; either version 2.1 of
12 * the License, or (at your option) any later version.
13 *
14 * ModeShape is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this software; if not, write to the Free
21 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
22 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
23 */
24 package org.modeshape.graph.observe;
25
26 import net.jcip.annotations.ThreadSafe;
27 import org.modeshape.common.util.Logger;
28 import org.modeshape.graph.GraphI18n;
29
30 /**
31 * A simple {@link Observer} that is itself {@link Observable}. This class essentially multiplexes the events from a single
32 * Observable to disseminate each event to multiple Observers.
33 */
34 @ThreadSafe
35 public class LocalObservationBus implements ObservationBus {
36 private final ChangeObservers observers = new ChangeObservers();
37 private static final Logger LOGGER = Logger.getLogger(LocalObservationBus.class);
38
39 public LocalObservationBus() {
40 }
41
42 /**
43 * {@inheritDoc}
44 *
45 * @see org.modeshape.graph.observe.ObservationBus#start()
46 */
47 public void start() {
48 // nothing to do
49 }
50
51 /**
52 * {@inheritDoc}
53 *
54 * @see org.modeshape.graph.observe.Observable#register(org.modeshape.graph.observe.Observer)
55 */
56 public boolean register( Observer observer ) {
57 if (observer == null) return false;
58 return observers.register(observer);
59 }
60
61 /**
62 * {@inheritDoc}
63 *
64 * @see org.modeshape.graph.observe.Observable#unregister(org.modeshape.graph.observe.Observer)
65 */
66 public boolean unregister( Observer observer ) {
67 return observers.unregister(observer);
68 }
69
70 /**
71 * {@inheritDoc}
72 *
73 * @see org.modeshape.graph.observe.Observer#notify(org.modeshape.graph.observe.Changes)
74 */
75 public void notify( Changes changes ) {
76 if (changes != null) {
77 // Broadcast the changes to the registered observers ...
78 try {
79 observers.broadcast(changes);
80 } catch (RuntimeException t) {
81 LOGGER.error(t, GraphI18n.errorNotifyingObserver, t.getLocalizedMessage());
82 }
83 }
84 }
85
86 /**
87 * {@inheritDoc}
88 *
89 * @see org.modeshape.graph.observe.ObservationBus#hasObservers()
90 */
91 public boolean hasObservers() {
92 return !observers.isEmpty();
93 }
94
95 /**
96 * {@inheritDoc}
97 *
98 * @see org.modeshape.graph.observe.ObservationBus#shutdown()
99 */
100 public void shutdown() {
101 observers.shutdown();
102 }
103 }