    001    /* $Id: VariableSubstitutor.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    package org.apache.commons.digester.substitution;
    020
    021    import org.apache.commons.digester.Substitutor;
    022
    023    import org.xml.sax.Attributes;
    024
    025    /**
    026     * Substitutor implementation that support variable replacement
    027     * for both attributes and body text.
    028     * The actual expansion of variables into text is delegated to {@link VariableExpander}
    029     * implementations.
    030     * Supports setting an expander just for body text or just for attributes.
    031     * Also supported is setting no expanders for body text and for attributes.
    032     *
    033     * @since 1.6
    034     */
    035    public class VariableSubstitutor extends Substitutor {
    036
    037        /**
    038         * The expander to be used to expand variables in the attributes.
    039         * Null when no expansion should be performed.
    040         */
    041        private VariableExpander attributesExpander;
    042
    043        /**
    044         * Attributes implementation that (lazily) performs variable substitution.
    045         * Will be lazily created when needed then reused.
    046         */
    047        private VariableAttributes variableAttributes;
    048
    049        /**
    050         * The expander to be used to expand variables in the body text.
    051         * Null when no expansion should be performed.
    052         */
    053        private VariableExpander bodyTextExpander;
    054
    055        /**
    056         * Constructs a Substitutor which uses the same VariableExpander for both
    057         * body text and attibutes.
    058         * @param expander VariableExpander implementation,
    059         * null if no substitutions are to be performed
    060         */
    061        public VariableSubstitutor(VariableExpander expander) {
    062            this(expander, expander);
    063        }
    064
    065        /**
    066         * Constructs a Substitutor.
    067         * @param attributesExpander VariableExpander implementation to be used for attributes,
    068         * null if no attribute substitutions are to be performed
    069         * @param bodyTextExpander VariableExpander implementation to be used for bodyTextExpander,
    070         * null if no attribute substitutions are to be performed
    071         */
    072        public VariableSubstitutor(VariableExpander attributesExpander, VariableExpander bodyTextExpander) {
    073            this.attributesExpander = attributesExpander;
    074            this.bodyTextExpander = bodyTextExpander;
    075            variableAttributes = new VariableAttributes();
    076        }
    077
    078        /**
    079         * Substitutes the attributes (before they are passed to the
    080         * <code>Rule</code> implementations's)
    081         */
    082        public Attributes substitute(Attributes attributes) {
    083            Attributes results = attributes;
    084            if (attributesExpander != null) {
    085                variableAttributes.init(attributes, attributesExpander);
    086                results = variableAttributes;
    087            }
    088            return results;
    089        }
    090
    091        /**
    092         * Substitutes for the body text.
    093         * This method may substitute values into the body text of the
    094         * elements that Digester parses.
    095         *
    096         * @param bodyText the body text (as passed to <code>Digester</code>)
    097         * @return the body text to be passed to the <code>Rule</code> implementations
    098         */
    099        public String substitute(String bodyText) {
    100            String result = bodyText;
    101            if (bodyTextExpander != null) {
    102                result = bodyTextExpander.expand(bodyText);
    103            }
    104            return result;
    105        }
    106    }