001// Copyright 2006, 2008 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 017import java.util.Collection; 018 019/** 020 * Defines how changes to fields (within components, within pages) may have their values persisted between requests. 021 * Different implementations store the field values {@linkplain org.apache.tapestry5.internal.services.SessionPersistentFieldStrategy 022 * in the session}, {@linkplain org.apache.tapestry5.internal.services.ClientPersistentFieldStrategy on the client}, or 023 * elsewhere. 024 */ 025public interface PersistentFieldStrategy 026{ 027 /** 028 * Posts a change of a persistent property. 029 * 030 * @param pageName the name of the page containing the component 031 * @param componentId the nested id path of the component (or null for the page's root component) 032 * @param fieldName the name of the field whose persistent value has changed 033 * @param newValue the new value for the field, possibly null 034 */ 035 void postChange(String pageName, String componentId, String fieldName, Object newValue); 036 037 /** 038 * Finds all persistent changes previously stored for the named page (for the current active session or client). 039 */ 040 Collection<PersistentFieldChange> gatherFieldChanges(String pageName); 041 042 /** 043 * Discards any saved changes for the name page. There is no expectation that data already gathered from the 044 * strategy and persumably dumped into component instance fields will be affected, but future field access (within 045 * this request or a later one) will show no data for the indicated page. 046 * 047 * @param pageName logical name of page whose field persistent data should be discarded 048 */ 049 void discardChanges(String pageName); 050}