01: /*
02: * Copyright 2002-2006 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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 doInTopLink(Session session) throws TopLinkException;
76:
77: }
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