    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}