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Java > Open Source Codes > org > apache > ojb > odmg > locking > LockManagerDefaultImpl


1 package org.apache.ojb.odmg.locking;
2
3 /* Copyright 2002-2005 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 org.apache.ojb.broker.Identity;
19 import org.apache.ojb.broker.util.logging.Logger;
20 import org.apache.ojb.broker.util.logging.LoggerFactory;
21 import org.apache.ojb.odmg.TransactionImpl;
22
23 /**
24  * The OJB default implementation of a Locking mechanism.
25  * This Implementation supports 4 transaction isolation levels
26  * as specified in the interface {@link org.apache.ojb.broker.locking.IsolationLevels}:
27  * public final int IL_READ_UNCOMMITTED = 0;
28  * public final int IL_READ_COMMITTED = 1;
29  * public final int IL_REPEATABLE_READ = 2;
30  * public final int IL_SERIALIZABLE = 3;
31  * Isolationlevels can be adjusted per class.
32  * The proper lockhandling is done in the respective LockStrategy implementation.
33  * This default implementation provides persistent Locks that are stored in
34  * a special database table.
35  * To keep the locks in the database and not in memory allows to use
36  * them accross multiple distributed ODMG clients.
37  *
38  * Of course this solution causes a lot of database reads and writes even if
39  * no real application data is written to the database. This solution may
40  * thus not be suited for all environments. As the LockManager is pluggable
41  * its possible to replace the default implementation by user defined
42  * implementations.
43  * A different solution might be to implement the LockManager as an additional
44  * standalone server, that allows to elminate additional db reads and writes.
45  *
46  * @author thma
47  * @deprecated
48  */
49 public class LockManagerDefaultImpl implements LockManager
50 {
51     private Logger log = LoggerFactory.getLogger(LockManagerDefaultImpl.class);
52
53     public LockManagerDefaultImpl()
54     {
55     }
56
57     /**
58      * aquires a readlock for transaction tx on object obj.
59      * Returns true if successful, else false.
60      */
61     public synchronized boolean readLock(TransactionImpl tx, Object JavaDoc obj)
62     {
63         if (log.isDebugEnabled()) log.debug("LM.readLock(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
64         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
65         return lockStrategy.readLock(tx, obj);
66     }
67
68     public boolean readLock(TransactionImpl tx, Identity oid, Object JavaDoc obj)
69     {
70         return readLock(tx,obj);
71     }
72
73     /**
74      * aquires a writelock for transaction tx on object obj.
75      * Returns true if successful, else false.
76      */
77     public synchronized boolean writeLock(TransactionImpl tx, Object JavaDoc obj)
78     {
79         if (log.isDebugEnabled()) log.debug("LM.writeLock(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
80         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
81         return lockStrategy.writeLock(tx, obj);
82     }
83
84     public boolean writeLock(TransactionImpl tx, Identity oid, Object JavaDoc obj)
85     {
86         return writeLock(tx, obj);
87     }
88
89     /**
90      * upgrades readlock for transaction tx on object obj to a writelock.
91      * If no readlock existed a writelock is acquired anyway.
92      * Returns true if successful, else false.
93      */
94     public synchronized boolean upgradeLock(TransactionImpl tx, Object JavaDoc obj)
95     {
96         if (log.isDebugEnabled()) log.debug("LM.upgradeLock(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
97         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
98         return lockStrategy.upgradeLock(tx, obj);
99     }
100
101     public boolean upgradeLock(TransactionImpl tx, Identity oid, Object JavaDoc obj)
102     {
103         return upgradeLock(tx, obj);
104     }
105
106     /**
107      * releases a lock for transaction tx on object obj.
108      * Returns true if successful, else false.
109      */
110     public synchronized boolean releaseLock(TransactionImpl tx, Object JavaDoc obj)
111     {
112         if (log.isDebugEnabled()) log.debug("LM.releaseLock(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
113         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
114         return lockStrategy.releaseLock(tx, obj);
115     }
116
117     public boolean releaseLock(TransactionImpl tx, Identity oid, Object JavaDoc obj)
118     {
119         return releaseLock(tx, obj);
120     }
121
122     /**
123      * checks if there is a readlock for transaction tx on object obj.
124      * Returns true if so, else false.
125      */
126     public synchronized boolean checkRead(TransactionImpl tx, Object JavaDoc obj)
127     {
128         if (log.isDebugEnabled()) log.debug("LM.checkRead(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
129         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
130         return lockStrategy.checkRead(tx, obj);
131     }
132
133     public boolean checkRead(TransactionImpl tx, Identity oid, Object JavaDoc obj)
134     {
135         return checkRead(tx, obj);
136     }
137
138     /**
139      * checks if there is a writelock for transaction tx on object obj.
140      * Returns true if so, else false.
141      */
142     public synchronized boolean checkWrite(TransactionImpl tx, Object JavaDoc obj)
143     {
144         if (log.isDebugEnabled()) log.debug("LM.checkWrite(tx-" + tx.getGUID() + ", " + new Identity(obj, tx.getBroker()).toString() + ")");
145         LockStrategy lockStrategy = LockStrategyFactory.getStrategyFor(obj);
146         return lockStrategy.checkWrite(tx, obj);
147     }
148
149     public boolean checkWrite(TransactionImpl tx, Identity oid, Object JavaDoc obj)
150     {
151         return checkWrite(tx, obj);
152     }
153 }
154
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