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Java > Open Source Codes > org > springframework > context > event > SimpleApplicationEventMulticaster


1 /*
2  * Copyright 2002-2006 the original author or authors.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.springframework.context.event;
18
19 import java.util.Iterator JavaDoc;
20
21 import org.springframework.context.ApplicationEvent;
22 import org.springframework.context.ApplicationListener;
23 import org.springframework.core.task.SyncTaskExecutor;
24 import org.springframework.core.task.TaskExecutor;
25
26 /**
27  * Simple implementation of the ApplicationEventMulticaster interface.
28  *
29  * <p>Multicasts all events to all registered listeners, leaving it up to
30  * the listeners to ignore events that they are not interested in.
31  * Listeners will usually perform corresponding <code>instanceof</code>
32  * checks on the passed-in event object.
33  *
34  * <p>By default, all listeners are invoked in the calling thread.
35  * This allows the danger of a rogue listener blocking the entire application,
36  * but adds minimal overhead. Specify an alternative TaskExecutor to have
37  * listeners executed in different threads, for example from a thread pool.
38  *
39  * @author Rod Johnson
40  * @author Juergen Hoeller
41  * @see #setTaskExecutor
42  */
43 public class SimpleApplicationEventMulticaster extends AbstractApplicationEventMulticaster {
44
45     private TaskExecutor taskExecutor = new SyncTaskExecutor();
46
47
48     /**
49      * Set the TaskExecutor to execute application listeners with.
50      * <p>Default is a SyncTaskExecutor, executing the listeners synchronously
51      * in the calling thread.
52      * <p>Consider specifying an asynchronous TaskExecutor here to not block the
53      * caller until all listeners have been executed. However, note that asynchronous
54      * execution will not participate in the caller's thread context (class loader,
55      * transaction association) unless the TaskExecutor explicitly supports this.
56      * @see org.springframework.core.task.SyncTaskExecutor
57      * @see org.springframework.core.task.SimpleAsyncTaskExecutor
58      * @see org.springframework.scheduling.timer.TimerTaskExecutor
59      */
60     public void setTaskExecutor(TaskExecutor taskExecutor) {
61         this.taskExecutor = (taskExecutor != null ? taskExecutor : new SyncTaskExecutor());
62     }
63
64     /**
65      * Return the current TaskExecutor for this multicaster.
66      */
67     protected TaskExecutor getTaskExecutor() {
68         return taskExecutor;
69     }
70
71
72     public void multicastEvent(final ApplicationEvent event) {
73         for (Iterator JavaDoc it = getApplicationListeners().iterator(); it.hasNext();) {
74             final ApplicationListener listener = (ApplicationListener) it.next();
75             getTaskExecutor().execute(new Runnable JavaDoc() {
76                 public void run() {
77                     listener.onApplicationEvent(event);
78                 }
79             });
80         }
81     }
82
83 }
84
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