001// Copyright 2007 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.internal.services;
016
017import org.apache.tapestry5.http.services.Request;
018import org.apache.tapestry5.http.services.Session;
019
020/**
021 * The "flash" strategy stores data inside the {@link Session session}, just like {@link
022 * SessionPersistentFieldStrategy}, but also removes the values from the session on first use. In this way, a short-term
023 * value (such as an error message) will "survive" from an action request to a render request and then disappear.
024 */
025public class FlashPersistentFieldStrategy extends AbstractSessionPersistentFieldStrategy
026{
027    /**
028     * Prefix used to identify keys stored in the session.
029     */
030    static final String PREFIX = "flash:";
031
032    public FlashPersistentFieldStrategy(Request request)
033    {
034        super(PREFIX, request);
035    }
036
037    @Override
038    protected void didReadChange(Session session, String attributeName)
039    {
040        // For flash persistence, after reading a value, get rid of it.
041        session.setAttribute(attributeName, null);
042    }
043
044}