Commons Digester example source code file (VariableSubstitutor.java)

This example Commons Digester source code file (VariableSubstitutor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

attributes, override, override, sax, string, string, substitutor, variableattributes, variableexpander, variableexpander, variablesubstitutor, variablesubstitutor

The Commons Digester VariableSubstitutor.java source code

/* $Id: VariableSubstitutor.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.digester.substitution;

import org.apache.commons.digester.Substitutor;

import org.xml.sax.Attributes;

/**
 * Substitutor implementation that support variable replacement
 * for both attributes and body text.
 * The actual expansion of variables into text is delegated to {@link VariableExpander}
 * implementations.
 * Supports setting an expander just for body text or just for attributes.
 * Also supported is setting no expanders for body text and for attributes. 
 *
 * @since 1.6
 */
public class VariableSubstitutor extends Substitutor {

    /** 
     * The expander to be used to expand variables in the attributes.
     * Null when no expansion should be performed.
     */
    private VariableExpander attributesExpander;
    
    /** 
     * Attributes implementation that (lazily) performs variable substitution.
     * Will be lazily created when needed then reused.
     */
    private VariableAttributes variableAttributes;
    
    /** 
     * The expander to be used to expand variables in the body text.
     * Null when no expansion should be performed.
     */
    private VariableExpander bodyTextExpander;
    
    /**
     * Constructs a Substitutor which uses the same VariableExpander for both
     * body text and attibutes.
     * @param expander VariableExpander implementation, 
     * null if no substitutions are to be performed
     */
    public VariableSubstitutor(VariableExpander expander) {
        this(expander, expander);
    }
    
    /**
     * Constructs a Substitutor.
     * @param attributesExpander VariableExpander implementation to be used for attributes, 
     * null if no attribute substitutions are to be performed
     * @param bodyTextExpander VariableExpander implementation to be used for bodyTextExpander, 
     * null if no attribute substitutions are to be performed     
     */
    public VariableSubstitutor(VariableExpander attributesExpander, VariableExpander bodyTextExpander) {
        this.attributesExpander = attributesExpander;
        this.bodyTextExpander = bodyTextExpander;
        variableAttributes = new VariableAttributes();
    }    

    /**
     * Substitutes the attributes (before they are passed to the 
     * <code>Rule implementations's)
     */
    @Override
    public Attributes substitute(Attributes attributes) {
        Attributes results = attributes;
        if (attributesExpander != null) {
            variableAttributes.init(attributes, attributesExpander);
            results = variableAttributes;
        }
        return results;
    }
    
    /**
     * Substitutes for the body text.
     * This method may substitute values into the body text of the
     * elements that Digester parses.
     *
     * @param bodyText the body text (as passed to <code>Digester)
     * @return the body text to be passed to the <code>Rule implementations
     */
    @Override
    public String substitute(String bodyText) {
        String result = bodyText;
        if (bodyTextExpander != null) {
            result = bodyTextExpander.expand(bodyText);
        }
        return result;
    }
}