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Java > Open Source Codes > org > jacorb > notification > queue > AbstractBoundedEventQueue


1 package org.jacorb.notification.queue;
2
3 /*
4  * JacORB - a free Java ORB
5  *
6  * Copyright (C) 1999-2004 Gerald Brose
7  *
8  * This library is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Library General Public
10  * License as published by the Free Software Foundation; either
11  * version 2 of the License, or (at your option) any later version.
12  *
13  * This library is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Library General Public License for more details.
17  *
18  * You should have received a copy of the GNU Library General Public
19  * License along with this library; if not, write to the Free
20  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21  *
22  */
23
24 import org.jacorb.notification.interfaces.Message;
25
26 /**
27  * @author Alphonse Bendt
28  * @version $Id: AbstractBoundedEventQueue.java,v 1.8 2005/02/14 00:11:10 alphonse.bendt Exp $
29  */
30
31 abstract public class AbstractBoundedEventQueue implements MessageQueue
32 {
33     private final Object JavaDoc lock_;
34
35     private final int capacity_;
36
37     private final EventQueueOverflowStrategy overflowStrategy_;
38
39     protected AbstractBoundedEventQueue(int capacity, EventQueueOverflowStrategy overflowStrategy,
40             Object JavaDoc lock)
41     {
42         lock_ = lock;
43         capacity_ = capacity;
44         overflowStrategy_ = overflowStrategy;
45     }
46
47     abstract protected Message getEarliestTimeout();
48
49     abstract protected Message getLeastPriority();
50
51     abstract protected Message getNextElement();
52
53     abstract protected Message getOldestElement();
54
55     abstract protected Message getYoungestElement();
56
57     abstract protected Message[] getElements(int max);
58
59     abstract protected void addElement(Message event);
60
61     abstract protected Message[] getAllElements();
62
63     public Message[] getAllMessages(boolean wait) throws InterruptedException JavaDoc
64     {
65         synchronized (lock_)
66         {
67             if (wait)
68             {
69                 return getAllBlocking();
70             }
71
72             return getAllElements();
73         }
74     }
75
76     /**
77      * @pre current thread own monitor lock_
78      */
79     private Message[] getAllBlocking() throws InterruptedException JavaDoc
80     {
81         while (isEmpty())
82         {
83             lock_.wait();
84         }
85
86         return getAllElements();
87     }
88
89     public Message getMessage(boolean wait) throws InterruptedException JavaDoc
90     {
91         synchronized (lock_)
92         {
93             if (wait)
94             {
95                 return getEventBlocking();
96             }
97
98             if (isEmpty())
99             {
100                 return null;
101             }
102
103             return getNextElement();
104         }
105     }
106
107     public Message[] getMessages(int max, boolean wait) throws InterruptedException JavaDoc
108     {
109         synchronized (lock_)
110         {
111             if (wait)
112             {
113                 return getEventsBlocking(max);
114             }
115
116             return getElements(max);
117         }
118     }
119
120     /**
121      * @pre current thread owns monitor lock_
122      */
123     private Message[] getEventsBlocking(int max) throws InterruptedException JavaDoc
124     {
125         while (isEmpty())
126         {
127             lock_.wait();
128         }
129
130         return getElements(max);
131     }
132
133     /**
134      * @pre current thread owns monitor lock_
135      */
136     private Message getEventBlocking() throws InterruptedException JavaDoc
137     {
138         while (isEmpty())
139         {
140             lock_.wait();
141         }
142
143         return getOldestElement();
144     }
145
146     public void put(Message event)
147     {
148         synchronized (lock_)
149         {
150             while (getSize() >= capacity_)
151             {
152                 overflowStrategy_.removeElementFromQueue(this);
153             }
154
155             addElement(event);
156
157             lock_.notifyAll();
158         }
159     }
160 }
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