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Java > Open Source Codes > org > apache > ojb > broker > util > collections > RemovalAwareSet


1 package org.apache.ojb.broker.util.collections;
2
3 /* Copyright 2003-2005 The Apache Software Foundation
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 import java.util.Iterator JavaDoc;
19 import java.util.Vector JavaDoc;
20 import org.apache.ojb.broker.PersistenceBroker;
21 import org.apache.ojb.broker.PersistenceBrokerException;
22
23 /**
24  * This is a set implementation that tracks removal and addition of elements.
25  * This tracking allow the PersistenceBroker to delete elements from
26  * the database that have been removed from the collection before a
27  * PB.store() orperation occurs.
28  * This will allow to use the PB api in way pretty close to ODMG persistent
29  * collections!
30  *
31  * @author Thomas Dudziak
32  * @version $Id: RemovalAwareSet.java,v 1.1.2.2 2005/12/21 22:28:15 tomdz Exp $
33  */
34 public class RemovalAwareSet extends ManageableHashSet implements IRemovalAwareCollection
35 {
36     private Vector JavaDoc allObjectsToBeRemoved = new Vector JavaDoc();
37
38     /**
39      * @see org.apache.ojb.broker.ManageableCollection#afterStore(PersistenceBroker broker)
40      */
41     public void afterStore(PersistenceBroker broker) throws PersistenceBrokerException
42     {
43         // make sure allObjectsToBeRemoved does not contain
44 // any instances that got re-added to the list
45 allObjectsToBeRemoved.removeAll(this);
46
47         Iterator JavaDoc iter = allObjectsToBeRemoved.iterator();
48         while (iter.hasNext())
49         {
50             broker.delete(iter.next());
51         }
52         allObjectsToBeRemoved.clear();
53     }
54
55     protected void registerForDeletion(Object JavaDoc toBeRemoved)
56     {
57         //only add objects once to avoid double deletions
58 if (!allObjectsToBeRemoved.contains(toBeRemoved))
59         {
60             this.allObjectsToBeRemoved.add(toBeRemoved);
61         }
62     }
63
64     /**
65      * @see java.util.Collection#remove(Object)
66      */
67     public boolean remove(Object JavaDoc o)
68     {
69         boolean result = super.remove(o);
70         registerForDeletion(o);
71         return result;
72     }
73
74     /**
75      * @see java.util.Vector#removeAllElements()
76      */
77     public synchronized void removeAllElements()
78     {
79         for (Iterator JavaDoc it = iterator(); it.hasNext();)
80         {
81             registerForDeletion(it.next());
82         }
83         super.clear();
84     }
85
86     public synchronized void clear()
87     {
88       removeAllElements();
89     }
90
91     public void resetDeleted()
92     {
93       this.allObjectsToBeRemoved.clear();
94     }
95     
96 }
97
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