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Java > Open Source Codes > org > apache > ojb > broker > core > PersistenceBrokerThreadMapping


1 package org.apache.ojb.broker.core;
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.Collection JavaDoc;
19 import java.util.HashMap JavaDoc;
20 import java.util.HashSet JavaDoc;
21 import java.util.Iterator JavaDoc;
22 import java.util.WeakHashMap JavaDoc;
23
24 import org.apache.ojb.broker.PBFactoryException;
25 import org.apache.ojb.broker.PBKey;
26 import org.apache.ojb.broker.PersistenceBrokerException;
27 import org.apache.ojb.broker.PersistenceBrokerInternal;
28
29 /**
30  * Helper class that tracks correspondence between PersistenceBroker instances
31  * and threads. The main task that this class solves is: to get current
32  * PersistenceBroker for the given thread. For internal use only.
33  *
34  * @author Oleg Nitz
35  * @version $Id: PersistenceBrokerThreadMapping.java,v 1.6.2.3 2005/12/21 22:25:01 tomdz Exp $
36  */
37 public class PersistenceBrokerThreadMapping
38 {
39     /**
40      * A Collection of all HashMaps added to the <CODE>ThreadLocal currentBrokerMap</CODE> that are still -alive-.
41      * If all the PersistenceBrokers are always correctly closed, the Collection should remain empty.
42      * The Collection is iterated trough when calling the <CODE>shutdown()</CODE> method and all the maps that are
43      * still alive will be cleared.
44      */
45     private static Collection JavaDoc loadedHMs = new HashSet JavaDoc();
46
47     /**
48      * The hashmap that maps PBKeys to current brokers for the thread
49      */
50     private static ThreadLocal JavaDoc currentBrokerMap = new ThreadLocal JavaDoc();
51
52     /**
53      * Mark a PersistenceBroker as preferred choice for current Thread
54      *
55      * @param key The PBKey the broker is associated to
56      * @param broker The PersistenceBroker to mark as current
57      */
58     public static void setCurrentPersistenceBroker(PBKey key, PersistenceBrokerInternal broker)
59             throws PBFactoryException
60     {
61         HashMap JavaDoc map = (HashMap JavaDoc) currentBrokerMap.get();
62         WeakHashMap JavaDoc set = null;
63         if(map == null)
64         {
65             map = new HashMap JavaDoc();
66             currentBrokerMap.set(map);
67
68             loadedHMs.add(map);
69         }
70         else
71         {
72             set = (WeakHashMap JavaDoc) map.get(key);
73         }
74
75         if(set == null)
76         {
77             // We emulate weak HashSet using WeakHashMap
78 set = new WeakHashMap JavaDoc();
79             map.put(key, set);
80         }
81         set.put(broker, null);
82     }
83
84     /**
85      * Unmark a PersistenceBroker as preferred choice for current Thread
86      *
87      * @param key The PBKey the broker is associated to
88      * @param broker The PersistenceBroker to unmark
89      */
90     public static void unsetCurrentPersistenceBroker(PBKey key, PersistenceBrokerInternal broker)
91             throws PBFactoryException
92     {
93         HashMap JavaDoc map = (HashMap JavaDoc) currentBrokerMap.get();
94         WeakHashMap JavaDoc set = null;
95         if(map != null)
96         {
97             set = (WeakHashMap JavaDoc) map.get(key);
98             if(set != null)
99             {
100                 set.remove(broker);
101                 if(set.isEmpty())
102                 {
103                     map.remove(key);
104                 }
105             }
106             if(map.isEmpty())
107             {
108                 currentBrokerMap.set(null);
109                 loadedHMs.remove(map);
110             }
111         }
112     }
113
114     /**
115      * Return the current open {@link org.apache.ojb.broker.PersistenceBroker}
116      * instance for the given {@link org.apache.ojb.broker.PBKey}, if any.
117      *
118      * @param key
119      * @return null if no open {@link org.apache.ojb.broker.PersistenceBroker} found.
120      */
121     public static PersistenceBrokerInternal currentPersistenceBroker(PBKey key)
122             throws PBFactoryException, PersistenceBrokerException
123     {
124         HashMap JavaDoc map = (HashMap JavaDoc) currentBrokerMap.get();
125         WeakHashMap JavaDoc set;
126         PersistenceBrokerInternal broker = null;
127
128         if(map == null)
129         {
130             return null;
131         }
132
133         set = (WeakHashMap JavaDoc) map.get(key);
134         if(set == null)
135         {
136             return null;
137         }
138
139         // seek for an open broker, preferably in transaction
140 for(Iterator JavaDoc it = set.keySet().iterator(); it.hasNext();)
141         {
142             PersistenceBrokerInternal tmp = (PersistenceBrokerInternal) it.next();
143             if(tmp == null || tmp.isClosed())
144             {
145                 it.remove();
146                 continue;
147             }
148             broker = tmp;
149             if(tmp.isInTransaction())
150             {
151                 break; // the best choice found
152 }
153         }
154         return broker;
155     }
156
157     /**
158      * Clean up static fields and any registered ThreadLocal contents to grant a clean
159      * shutdown/reload of OJB within re/hot-deployable applications.
160      */
161     public static void shutdown()
162     {
163         for(Iterator JavaDoc it = loadedHMs.iterator(); it.hasNext();)
164         {
165             ((HashMap JavaDoc) it.next()).clear();
166         }
167         loadedHMs.clear();
168         loadedHMs = null;
169         currentBrokerMap = null;
170     }
171 }
172
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