001    // Copyright 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    
015    package org.apache.tapestry.record;
016    
017    import java.util.List;
018    
019    /**
020     * Responsible for encoding {@link org.apache.tapestry.record.PropertyChange}s
021     * into and out of plain strings.
022     * 
023     * @author Howard M. Lewis Ship
024     * @since 4.0
025     */
026    public interface PersistentPropertyDataEncoder
027    {
028    
029        /**
030         * Encodes a (possibly empty) list of {@link PropertyChange}s into a string
031         * representation that can later be decoded.
032         *
033         * @param changes
034         *          List of changes to encode into a persistable form.
035         * 
036         * @return encoded string (possibly empty, but not null)
037         */
038        String encodePageChanges(List changes);
039    
040        /**
041         * Takes a string with an encoded set of page changes, and converts it back
042         * into a list of {@link org.apache.tapestry.record.PropertyChange}s.
043         *
044         * @param encoded
045         *          The data to un-encode, which should be equivalent to the same that
046         *          was passed in to {@link #encodePageChanges(java.util.List)}.
047         * 
048         * @return The decoded page data.
049         */
050    
051        List decodePageChanges(String encoded);
052    
053    }