001// Copyright 2006 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.services;
016
017/**
018 * Encapsulates persisted property information for an entire page.
019 */
020public interface PersistentFieldBundle
021{
022    /**
023     * Checks to see if a persistent value has been stored for the indicated component and field. TODO: This method can
024     * probably be removed; it doesn't look like its used (instead, we if check getValue() returns null).
025     *
026     * @param componentId the nested id of the component (within the page), may be null or blank for the root component
027     *                    of the page
028     * @param fieldName   the name of the field whose value was persisted
029     * @return true if a change has been stored
030     */
031    boolean containsValue(String componentId, String fieldName);
032
033    /**
034     * @param componentId the nested if of the component (within the page), may be null or blank for the root component
035     *                    of the page
036     * @param fieldName   the name of the field whose value was persisted
037     * @return the persisted value, possibly null
038     */
039    Object getValue(String componentId, String fieldName);
040}