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Java > Open Source Codes > com > presumo > jms > plugin > implementation > MemoryMessageQueue


1 /**
2  * This file is part of Presumo.
3  *
4  * Presumo is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * Presumo is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with Presumo; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17  *
18  *
19  * Copyright 2001 Dan Greff
20  */
21 package com.presumo.jms.plugin.implementation;
22
23 import com.presumo.jms.message.JmsMessage;
24 import com.presumo.jms.plugin.MessageQueue;
25
26 import java.io.IOException JavaDoc;
27 import java.util.LinkedList JavaDoc;
28
29 /**
30  * Implementation of the MessageQueue interface in which all messages
31  * reside in memory. Used by RemoteSession and JmsSession due to some
32  * nasty design shortcuts. Currently also used by Router, but that
33  * will eventually be replaced by an implementation that transactionally
34  * writes persistent messages to disk and leaves non-persistent messages
35  * in memory.
36  *
37  * @author Dan Greff
38  */
39 public class MemoryMessageQueue implements MessageQueue
40 {
41   // A simpler LinkedList implementation would probably speed things
42 // up dramatically. If somebody does decide to try putting one in
43 // be sure to do before and after performance test. If the performance
44 // isn't dramatically better, we should probably stay with the javasoft
45 // version.
46 private final LinkedList JavaDoc list = new LinkedList JavaDoc();
47   
48   public MemoryMessageQueue()
49   {
50   }
51
52   public void push(JmsMessage msg) throws IOException JavaDoc
53   {
54     list.add(msg);
55   }
56   
57   public void push(JmsMessage [] msgs) throws IOException JavaDoc
58   {
59     for (int i=0; i < msgs.length; ++i)
60       list.add( msgs[i] );
61   }
62   
63   public JmsMessage getNext() throws IOException JavaDoc
64   {
65     return (JmsMessage) list.removeFirst();
66   }
67   
68   public JmsMessage [] getNext(int batchsize) throws IOException JavaDoc
69   {
70     JmsMessage [] msgs;
71     if (batchsize < list.size()) {
72       msgs = new JmsMessage[batchsize];
73       for (int i=0; i < batchsize; ++i)
74         msgs[i] = (JmsMessage) list.removeFirst();
75     }
76     else {
77       msgs = new JmsMessage[list.size()];
78       list.toArray(msgs);
79       list.clear();
80     }
81     return msgs;
82   }
83   
84   public void delete(String JavaDoc key) throws IOException JavaDoc
85   {
86   }
87   
88   public void delete(String JavaDoc [] keys) throws IOException JavaDoc
89   {
90   }
91
92   public int size()
93   {
94     return list.size();
95   }
96   
97   public void close() throws IOException JavaDoc
98   {
99     // only relevant for persistent storage queue implementations
100 }
101   
102   public boolean isPersistent()
103   {
104     return false;
105   }
106 }
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