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Java > Open Source Codes > org > apache > tapestry > engine > IPageRecorder


1 // Copyright 2004, 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry.engine;
16
17 import org.apache.tapestry.IPage;
18 import org.apache.tapestry.event.ChangeObserver;
19
20 /**
21  * Defines an object that can observe changes to properties of a page and its components, store the
22  * state of the page between request cycles, and restore a page's state on a subsequent request
23  * cycle.
24  * <p>
25  * Concrete implementations of this can store the changes in memory, as client-side cookies, in a
26  * flat file, or in a database.
27  *
28  * @author Howard Lewis Ship
29  */
30
31 public interface IPageRecorder extends ChangeObserver
32 {
33     /**
34      * Persists all changes that have been accumulated. If the recorder saves change incrementally,
35      * this should ensure that all changes have been persisted.
36      * <p>
37      * After commiting, a page recorder automatically locks itself.
38      */
39
40     public void commit();
41
42     /**
43      * Rolls back the page to the currently persisted state.
44      * <p>
45      * A page recorder can only rollback changes to properties which have changed at some point.
46      * This can cause some minor problems, addressed by
47      * {@link org.apache.tapestry.event.PageDetachListener#pageDetached(org.apache.tapestry.event.PageEvent)}.
48      */
49
50     public void rollback(IPage page);
51 }
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