    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
    015    package org.apache.tapestry5.services;
    016
    017    /**
    018     * Encapsulates persisted property information for an entire page.
    019     */
    020    public 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    }