01: // Copyright 2007 The Apache Software Foundation
02: //
03: // Licensed under the Apache License, Version 2.0 (the "License");
04: // you may not use this file except in compliance with the License.
05: // You may obtain a copy of the License at
06: //
07: // http://www.apache.org/licenses/LICENSE-2.0
08: //
09: // 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.internal.services;
16:
17: import org.apache.tapestry.services.Request;
18: import org.apache.tapestry.services.Session;
19:
20: /**
21: * The "flash" strategy stores data inside the {@link Session session}, just like
22: * {@link SessionPersistentFieldStrategy}, but also removes the values from the session on first
23: * use. In this way, a short-term value (such as an error message) will "survive" from an action
24: * request to a render request and then disappear.
25: */
26: public class FlashPersistentFieldStrategy extends
27: AbstractSessionPersistentFieldStrategy {
28: /**
29: * Prefix used to identify keys stored in the session.
30: */
31: static final String PREFIX = "flash:";
32:
33: public FlashPersistentFieldStrategy(Request request) {
34: super (PREFIX, request);
35: }
36:
37: @Override
38: protected void didReadChange(Session session, String attributeName) {
39: // For flash persistence, after reading a value, get rid of it.
40: session.setAttribute(attributeName, null);
41: }
42:
43: }
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