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    }