001// Copyright 2004, 2005 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.tapestry.engine; 016 017import org.apache.tapestry.IPage; 018import org.apache.tapestry.event.ChangeObserver; 019 020/** 021 * Defines an object that can observe changes to properties of a page and its components, store the 022 * state of the page between request cycles, and restore a page's state on a subsequent request 023 * cycle. 024 * <p> 025 * Concrete implementations of this can store the changes in memory, as client-side cookies, in a 026 * flat file, or in a database. 027 * 028 * @author Howard Lewis Ship 029 */ 030 031public interface IPageRecorder extends ChangeObserver 032{ 033 /** 034 * Persists all changes that have been accumulated. If the recorder saves change incrementally, 035 * this should ensure that all changes have been persisted. 036 * <p> 037 * After commiting, a page recorder automatically locks itself. 038 */ 039 040 public void commit(); 041 042 /** 043 * Rolls back the page to the currently persisted state. 044 * <p> 045 * A page recorder can only rollback changes to properties which have changed at some point. 046 * This can cause some minor problems, addressed by 047 * {@link org.apache.tapestry.event.PageDetachListener#pageDetached(org.apache.tapestry.event.PageEvent)}. 048 */ 049 050 public void rollback(IPage page); 051}