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Java > Open Source Codes > org > springframework > orm > toplink > UnitOfWorkCallback


1 /*
2  * Copyright 2002-2005 the original author or authors.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.springframework.orm.toplink;
18
19 import oracle.toplink.exceptions.TopLinkException;
20 import oracle.toplink.sessions.Session;
21 import oracle.toplink.sessions.UnitOfWork;
22
23 /**
24  * Convenient abstract implementation of the TopLinkCallback interface,
25  * exposing a UnitOfWork to perform write operations on.
26  *
27  * <p>The exposed UnitOfWork will either be be the active UnitOfWork of
28  * the current transaction, if any, or a temporarily acquired UnitOfWork
29  * that will be committed at the end of the operation.
30  *
31  * @author Juergen Hoeller
32  * @since 1.2
33  * @see #doInUnitOfWork(oracle.toplink.sessions.UnitOfWork)
34  * @see oracle.toplink.sessions.Session#getActiveUnitOfWork()
35  */
36 public abstract class UnitOfWorkCallback implements TopLinkCallback {
37
38     /**
39      * Determines the UnitOfWork to work on (either the active UnitOfWork or a
40      * temporarily acquired UnitOfWork) and delegates to <code>doInUnitOfWork</code>.
41      * @see #doInUnitOfWork(oracle.toplink.sessions.UnitOfWork)
42      */
43     public final Object JavaDoc doInTopLink(Session session) throws TopLinkException {
44         // Fetch active UnitOfWork or acquire temporary UnitOfWork.
45 UnitOfWork unitOfWork = session.getActiveUnitOfWork();
46         boolean newUnitOfWork = false;
47         if (unitOfWork == null) {
48             unitOfWork = session.acquireUnitOfWork();
49             newUnitOfWork = true;
50         }
51
52         // Perform callback operation, committing the UnitOfWork unless
53 // it is the active UnitOfWork of an externally managed transaction.
54 try {
55             Object JavaDoc result = doInUnitOfWork(unitOfWork);
56             if (newUnitOfWork) {
57                 unitOfWork.commit();
58             }
59             return result;
60         }
61         finally {
62             if (newUnitOfWork) {
63                 unitOfWork.release();
64             }
65         }
66     }
67
68     /**
69      * Called with a UnitOfWork to work on, either the active UnitOfWork or a
70      * temporarily acquired UnitOfWork (as determined by the transaction status).
71      * @param unitOfWork the TopLink UnitOfWork to perform write operations on
72      * @return a result object, or <code>null</code> if none
73      * @throws TopLinkException in case of TopLink errors
74      */
75     protected abstract Object JavaDoc doInUnitOfWork(UnitOfWork unitOfWork) throws TopLinkException;
76
77 }
78
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