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1   /*** 
2    * 
3    * Copyright 2004 Protique Ltd
4    * 
5    * Licensed under the Apache License, Version 2.0 (the "License"); 
6    * you may not use this file except in compliance with the License. 
7    * You may obtain a copy of the License at 
8    * 
9    * http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS, 
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
14   * See the License for the specific language governing permissions and 
15   * limitations under the License. 
16   * 
17   **/
18  
19  package org.codehaus.activemq;
20  
21  import org.codehaus.activemq.message.Packet;
22  import org.codehaus.activemq.util.BitArrayBin;
23  import org.codehaus.activemq.util.IdGenerator;
24  import org.codehaus.activemq.util.LRUCache;
25  
26  import javax.jms.Message;
27  import java.util.LinkedHashMap;
28  
29  /***
30   * Provides basic audit functions for Messages
31   *
32   * @version $Revision: 1.4 $
33   */
34  public class ActiveMQMessageAudit {
35      private static final int DEFAULT_WINDOW_SIZE = 1024;
36      private static final int MAXIMUM_PRODUCER_COUNT = 128;
37      private int windowSize;
38      private LinkedHashMap map;
39  
40      /***
41       * Default Constructor windowSize = 1024, maximumNumberOfProducersToTrack = 128
42       */
43      public ActiveMQMessageAudit() {
44          this(DEFAULT_WINDOW_SIZE, MAXIMUM_PRODUCER_COUNT);
45      }
46  
47      /***
48       * Construct a MessageAudit
49       *
50       * @param windowSize range of ids to track
51       * @param maximumNumberOfProducersToTrack
52       *                   number of producers expected in the system
53       */
54      public ActiveMQMessageAudit(int windowSize, final int maximumNumberOfProducersToTrack) {
55          this.windowSize = windowSize;
56          map = new LRUCache(maximumNumberOfProducersToTrack);
57      }
58  
59      /***
60       * Checks if this message has beeb seen before
61       *
62       * @param message
63       * @return true if the message is a duplicate
64       */
65      public boolean isDuplicate(Message message) {
66          if (message instanceof Packet) {
67              return isDuplicate((Packet) message);
68          }
69          return false;
70      }
71  
72      /***
73       * checks whether this messageId has been seen before
74       *
75       * @param packet
76       * @return true if the message is a duplicate
77       */
78      public boolean isDuplicate(Packet packet) {
79          return isDuplicate(packet.getId());
80      }
81  
82      /***
83       * checks whether this messageId has been seen before and adds this messageId to the list
84       *
85       * @param id
86       * @return true if the message is a duplicate
87       */
88      public boolean isDuplicate(String id) {
89          boolean answer = false;
90          String seed = IdGenerator.getSeedFromId(id);
91          if (seed != null) {
92              BitArrayBin bab = (BitArrayBin) map.get(seed);
93              if (bab == null) {
94                  bab = new BitArrayBin(windowSize);
95                  map.put(seed, bab);
96              }
97              long index = IdGenerator.getCountFromId(id);
98              if (index >= 0) {
99                  answer = bab.setBit(index, true);
100             }
101         }
102         return answer;
103     }
104 }