Commons Digester example source code file (MarkupDigester.java)

This example Commons Digester source code file (MarkupDigester.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, digester, list, markupdigester, markupdigester, parser, rule, sax, saxexception, saxexception, string, string, stringbuffer, textsegmenthandler, textsegmenthandler, util, xml

The Commons Digester MarkupDigester.java source code

/*
 * 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.
 */ 

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.Rule;

import java.util.List;
import javax.xml.parsers.SAXParser;
import org.xml.sax.XMLReader;
import org.xml.sax.SAXException;
import org.xml.sax.Attributes;

/**
 * This is a subclass of digester which supports rules which implement
 * the TextSegmentHandler interface, causing the "textSegment" method
 * on each matching rule (of the appropriate type) to be invoked when
 * an element contains a segment of text followed by a child element.
 * <p>
 * See the readme file included with this example for more information.
 */
 
public class MarkupDigester extends Digester {

    /** See equivalent constructor in Digester class. */
    public MarkupDigester() {
    }

    /** See equivalent constructor in Digester class. */
    public MarkupDigester(SAXParser parser) {
        super(parser);
    }

    /** See equivalent constructor in Digester class. */
    public MarkupDigester(XMLReader reader) {
        super(reader);
    }

    //===================================================================

    /**
     * The text found in the current element since the last child element.
     */
    protected StringBuffer currTextSegment = new StringBuffer();

    /**
     * Process notification of character data received from the body of
     * an XML element.
     *
     * @param buffer The characters from the XML document
     * @param start Starting offset into the buffer
     * @param length Number of characters from the buffer
     *
     * @exception SAXException if a parsing error is to be reported
     */
    public void characters(char buffer[], int start, int length)
            throws SAXException {

        super.characters(buffer, start, length);
        currTextSegment.append(buffer, start, length);
    }

    /**
     * Process notification of the start of an XML element being reached.
     *
     * @param namespaceURI The Namespace URI, or the empty string if the element
     *   has no Namespace URI or if Namespace processing is not being performed.
     * @param localName The local name (without prefix), or the empty
     *   string if Namespace processing is not being performed.
     * @param qName The qualified name (with prefix), or the empty
     *   string if qualified names are not available.
     * @param list The attributes attached to the element. If there are
     *   no attributes, it shall be an empty Attributes object. 
     * @exception SAXException if a parsing error is to be reported
     */
 
    public void startElement(String namespaceURI, String localName,
                             String qName, Attributes list)
            throws SAXException {

        handleTextSegments();

        // Unlike bodyText, which accumulates despite intervening child
        // elements, currTextSegment gets cleared here. This means that
        // we don't need to save it on a stack either.
        currTextSegment.setLength(0);

        super.startElement(namespaceURI, localName, qName, list);
    }

    /**
     * Process notification of the end of an XML element being reached.
     *
     * @param namespaceURI - The Namespace URI, or the empty string if the
     *   element has no Namespace URI or if Namespace processing is not
     *   being performed.
     * @param localName - The local name (without prefix), or the empty
     *   string if Namespace processing is not being performed.
     * @param qName - The qualified XML 1.0 name (with prefix), or the
     *   empty string if qualified names are not available.
     * @exception SAXException if a parsing error is to be reported
     */
    public void endElement(String namespaceURI, String localName,
                           String qName) throws SAXException {
 
        handleTextSegments();
        currTextSegment.setLength(0);
        super.endElement(namespaceURI, localName, qName);
     }

    /**
     * Iterate over the list of rules most recently matched, and
     * if any of them implement the TextSegmentHandler interface then
     * invoke that rule's textSegment method passing the current
     * segment of text from the xml element body.
     */
    private void handleTextSegments() throws SAXException {    
        if (currTextSegment.length() > 0) {
            String segment = currTextSegment.toString();
            List parentMatches = (List) matches.peek();
            int len = parentMatches.size();
            for(int i=0; i<len; ++i) {
                Rule r = (Rule) parentMatches.get(i);
                if (r instanceof TextSegmentHandler) {
                    TextSegmentHandler h = (TextSegmentHandler) r;
                    try {
                        h.textSegment(segment);
                    } catch(Exception e) {
                        throw createSAXException(e);
                    }
                }
            }
        }
    }
}