01: package org.apache.ojb.otm.lock.isolation;
02:
03: /* Copyright 2003-2005 The Apache Software Foundation
04: *
05: * Licensed under the Apache License, Version 2.0 (the "License");
06: * you may not use this file except in compliance with the License.
07: * You may obtain a copy of the License at
08: *
09: * 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.otm.core.Transaction;
19: import org.apache.ojb.otm.lock.LockingException;
20: import org.apache.ojb.otm.lock.ObjectLock;
21:
22: /**
23: *
24: * READ_COMMITTED IsolationStrategy.
25: *
26: * @author <a href="mailto:rraghuram@hotmail.com">Raghu Rajah</a>
27: * @author Thomas Mahler & David Dixon-Peugh
28: *
29: */
30: public class ReadCommittedIsolation extends AbstractIsolation {
31:
32: /**
33: * @see org.apache.ojb.otm.lock.TransactionIsolation#readLock(Transaction, ObjectLocks)
34: */
35: public void readLock(Transaction tx, ObjectLock lock)
36: throws LockingException {
37: Transaction writer = lock.getWriter();
38: if (writer == null) {
39: lock.readLock(tx);
40: if (lock.getWriter() != null) {
41: lock.releaseLock(tx);
42: readLock(tx, lock);
43: }
44: } else if (tx != writer) {
45: lock.waitForTx(writer);
46: readLock(tx, lock);
47: }
48: // else if tx is the writer, it can also read.
49: }
50:
51: /**
52: * @see org.apache.ojb.otm.lock.TransactionIsolation#writeLock(Transaction, ObjectLocks)
53: */
54: public void writeLock(Transaction tx, ObjectLock lock)
55: throws LockingException {
56: lock.writeLock(tx);
57: }
58:
59: }
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