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Java > Open Source Codes > org > exolab > jms > events > Event


1 /**
2  * Redistribution and use of this software and associated documentation
3  * ("Software"), with or without modification, are permitted provided
4  * that the following conditions are met:
5  *
6  * 1. Redistributions of source code must retain copyright
7  * statements and notices. Redistributions must also contain a
8  * copy of this document.
9  *
10  * 2. Redistributions in binary form must reproduce the
11  * above copyright notice, this list of conditions and the
12  * following disclaimer in the documentation and/or other
13  * materials provided with the distribution.
14  *
15  * 3. The name "Exolab" must not be used to endorse or promote
16  * products derived from this Software without prior written
17  * permission of Exoffice Technologies. For written permission,
18  * please contact info@exolab.org.
19  *
20  * 4. Products derived from this Software may not be called "Exolab"
21  * nor may "Exolab" appear in their names without prior written
22  * permission of Exoffice Technologies. Exolab is a registered
23  * trademark of Exoffice Technologies.
24  *
25  * 5. Due credit should be given to the Exolab Project
26  * (http://www.exolab.org/).
27  *
28  * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
29  * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
30  * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
31  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
32  * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
33  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
34  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
37  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
39  * OF THE POSSIBILITY OF SUCH DAMAGE.
40  *
41  * Copyright 2000,2003 (C) Exoffice Technologies Inc. All Rights Reserved.
42  *
43  * $Id: Event.java,v 1.1 2004/11/26 01:50:41 tanderson Exp $
44  *
45  * Date Author Changes
46  * 07/27/00 jima Created
47  */
48 package org.exolab.jms.events;
49
50 import java.io.Serializable JavaDoc;
51
52
53 /**
54  * This class specifies the object that is used by the {@link EventManager}.
55  * It defines the event type, the event listener and the callback object.
56  * <p>
57  * The event type is an integral value that identifies the type of event to
58  * fire. It is transparent to the {@link EventManager}.
59  * <p>
60  * The event listener must implement the {@link EventHandler} interface.
61  * <p>
62  * The callback object must be {@link Serializable} and is passed back to the
63  * {@link EventHandler} when the event fires.
64  * <p>
65  * Most importantly this class is {@link Serializable} so that it can be
66  * stored, if required.
67  *
68  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:41 $
69  * @author <a HREF="mailto:jima@intalio.com">Jim Alateras</a>
70  */
71 public class Event
72     implements Serializable JavaDoc {
73
74     /**
75      * The event type.
76      */
77     private int _eventType;
78
79     /**
80      * The _eventHandler is the object that is notified when the event fires.
81      * It must be Serializable so that it can be persisted.
82      */
83     private EventHandler _eventHandler = null;
84
85     /**
86      * The _callbackObject is optionally specified and is passed back to the
87      * _eventHandler during notification.
88      */
89     private Object JavaDoc _callbackObject = null;
90
91
92     /**
93      * The constructor instantiates an instance of this class with the
94      * specified parameters. The event and listener must be non-null and
95      * valid but the callback object may be null.
96      *
97      * @param event the type of event to fire
98      * @param listener the object that will receive the event
99      * @param callback a callback object, that is Serializable
100      * @throws IllegalEventDefinedException
101      */
102     public Event(int event, EventHandler listener, Object JavaDoc callback)
103         throws IllegalEventDefinedException {
104         if ((event != 0) &&
105             (listener != null)) {
106             _eventType = event;
107             _eventHandler = listener;
108
109             // if the callback object has been specified then ensure that
110 // it is Serializabe. If the object isnot Serializable then throw
111 // an exception.
112 if (callback != null) {
113                 if (callback instanceof Serializable JavaDoc) {
114                     _callbackObject = callback;
115                 } else {
116                     throw new IllegalEventDefinedException(
117                         "The callback object is not Serializable");
118                 }
119             }
120         } else {
121             // event not-well specified
122 throw new IllegalEventDefinedException(
123                 "event is 0 or listener is null");
124         }
125     }
126
127     /**
128      * Return the event type.
129      *
130      * @return int
131      */
132     public int getEventType() {
133         return _eventType;
134     }
135
136     /**
137      * Return the event listener
138      *
139      * @return EventHandler
140      */
141     public EventHandler getEventListener() {
142         return _eventHandler;
143     }
144
145     /**
146      * Return a reference to the callbacl object. The returned object may be
147      * null
148      *
149      * @return Object
150      */
151     public Object JavaDoc getCallbackObject() {
152         return _callbackObject;
153     }
154 }
155
156
157
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