001    /* $Id: VariableExpander.java 471661 2006-11-06 08:09:25Z skitching $
002     *
003     * Licensed to the Apache Software Foundation (ASF) under one or more
004     * contributor license agreements.  See the NOTICE file distributed with
005     * this work for additional information regarding copyright ownership.
006     * The ASF licenses this file to You under the Apache License, Version 2.0
007     * (the "License"); you may not use this file except in compliance with
008     * the License.  You may obtain a copy of the License at
009     * 
010     *      http://www.apache.org/licenses/LICENSE-2.0
011     * 
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */ 
018    
019    
020    package org.apache.commons.digester.substitution;
021    
022    /**
023     * <p>An Interface describing a class capable of expanding strings which
024     * may contain variable references. The exact syntax of the "reference",
025     * and the mechanism for determining the corresponding value to be used
026     * is up to the concrete implementation.</p>
027     *
028     * @since 1.6
029     */
030    public interface VariableExpander {
031        /**
032         * Return the input string with any variables replaced by their
033         * corresponding value. If there are no variables in the string,
034         * then the input parameter is returned unaltered.
035         */
036        public String expand(String param);
037    }
038