001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.configuration2.convert;
018
019/**
020 * <p>
021 * Definition of an interface used by {@link ListDelimiterHandler} to perform additional transformations on behalf of a
022 * configuration when a property value is escaped.
023 * </p>
024 * <p>
025 * Some {@code Configuration} implementations require a special encoding of their property values before they get
026 * written on disk. In some constellations, e.g. when a property with multiple values is to be forced on a single line,
027 * this encoding has to be done together with the escaping of list delimiter characters - which is in the responsibility
028 * of {@link ListDelimiterHandler}.
029 * </p>
030 * <p>
031 * In order to allow a proper collaboration between the parties involved, this interface was introduced. A configuration
032 * object provides an implementation of {@code ValueTransformer} and passes it to the {@code ListDelimiterHandler} when
033 * escaping of properties is needed. The delimiter handler can then call back to perform the additional encoding as its
034 * pleasure.
035 * </p>
036 *
037 * @since 2.0
038 */
039public interface ValueTransformer {
040    /**
041     * Performs an arbitrary encoding of the passed in value object. This method is called by a {@link ListDelimiterHandler}
042     * implementation before or after list delimiters have been escaped.
043     *
044     * @param value the property value to be transformed
045     * @return the transformed property value
046     */
047    Object transformValue(Object value);
048}