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


1 /*
2  * Copyright 2002-2006 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
22 /**
23  * Callback interface for TopLink code. To be used with {@link TopLinkTemplate}'s
24  * execution methods, often as anonymous classes within a method implementation.
25  * A typical implementation will call TopLink Session CRUD to perform some
26  * operations on persistent objects.
27  *
28  * <p>The <code>Session</code> that gets passed into the <code>doInTopLink</code> method
29  * is usually a thread-safe <code>ClientSession</code>. Since this provides access to the
30  * TopLink shared cache, it is possible for implementations of this interface to return
31  * references to <i>read-only objects from the shared cache</i>. These objects
32  * <i>must not be modified</i> by application code outside of the DAO layer.
33  * If persistent objects need to be edited, they should be loaded from (or registered with)
34  * a TopLink UnitOfWork, or they should be explicitly copied and merged back into a
35  * <code>UnitOfWork</code> at a later point of time.
36  *
37  * <p>Users can access a <code>UnitOfWork</code> by using the <code>getActiveUnitOfWork</code>
38  * method on the <code>Session</code>. Normally, this will only be done when there is an
39  * active non-read-only transaction being managed by Spring's {@link TopLinkTransactionManager}
40  * or by an external transaction controller (usually a J2EE server's JTA provider,
41  * configured in TopLink). The <code>getActiveUnitOfWork</code> method will return
42  * <code>null</code> outside of a managed transaction.
43  *
44  * @author Juergen Hoeller
45  * @author <a HREF="mailto:@james.x.clark@oracle.com">James Clark</a>
46  * @see TopLinkTemplate
47  * @see TopLinkTransactionManager
48  */
49 public interface TopLinkCallback {
50
51     /**
52      * Gets called by <code>TopLinkTemplate.execute</code> with an active
53      * <code>Session</code>. Does not need to care about activating or closing
54      * the TopLink <code>Session</code>, or handling transactions.
55      *
56      * <p>Note that write operations should usually be performed on the active
57      * <code>UnitOfWork</code> within an externally controlled transaction, through
58      * calling <code>getActiveUnitOfWork</code>. However, an implementation can also
59      * choose to use <code>acquireUnitOfWork</code> to create an independent
60      * <code>UnitOfWork</code>, which it needs to commit at the end of the operation.
61      *
62      * <p>Allows for returning a result object created within the callback,
63      * i.e. a domain object or a collection of domain objects.
64      * A thrown custom RuntimeException is treated as an application exception:
65      * It gets propagated to the caller of the template.
66      *
67      * @param session active TopLink Session
68      * @return a result object, or <code>null</code> if none
69      * @throws TopLinkException if thrown by the TopLink API
70      * @see oracle.toplink.sessions.Session#getActiveUnitOfWork()
71      * @see oracle.toplink.sessions.Session#acquireUnitOfWork()
72      * @see TopLinkTemplate#execute
73      * @see TopLinkTemplate#executeFind
74      */
75     Object JavaDoc doInTopLink(Session session) throws TopLinkException;
76
77 }
78
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