Is there a way to use a progress bar with Xerces XML Parser?

Question

My program is parsing very long XML files that take several minutes to parse. I am using Xerces as the parser. I would like to use a progress bar to show the progress, but I haven't found any way to get Xerces to give progress updates. Is this possible?

Answer 1

Use teh SAX parser and listen to SAX events. Example:
import java.io.*;
import java.util.*;
//jaxp-api.jar:
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
//sax.jar:
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import mine.IOUtils;
* Handler to read content from (large) XML sources and send events to registered XMLListeners. Use this class to read
* big (multiple megabytes) XML files via SAX and listen to XML events to process XML elements.
* For small (less than a megabyte) XML files, it's more convenient to use the DOM API
* to read the XML into a DOM document and perform XPath commands. DOM is easier to handle but has
* the drawback that the complete XML content is stored in one big DOM document object in memory.
public final class XMLHandler extends DefaultHandler {
    /** (Reusable) XMLReader to parse an XML document. */
    private XMLReader xmlReader = null;
    /** Registered XMLEventListeners. */
    private List<XMLListener> listeners = new ArrayList<XMLListener>();
    /** Value of current element. */
    private StringBuilder elementValue = null;
    /** Stack of current element and all of its parent elements. */
    private Stack<String> elementStack = new Stack<String>();
     * Constructor.
     * @throws Exception
    public XMLHandler() throws Exception {
        super();
        // Create a JAXP SAXParserFactory and configure it
        final SAXParserFactory spf = SAXParserFactory.newInstance(); //Use the default (non-validating) parser
        spf.setValidating(true);
        // Create a JAXP SAXParser
        final SAXParser saxParser = spf.newSAXParser();
        // Get the encapsulated SAX XMLReader
        xmlReader = saxParser.getXMLReader();
        xmlReader.setContentHandler(this);
        xmlReader.setDTDHandler(this);
        xmlReader.setEntityResolver(this);
        xmlReader.setErrorHandler(this);
    }//XMLHandler()
      * Add XMLListener to receive XML events from the current XML document.
     *  If <i>listener</i> is null, no exception is thrown and no action is performed.
      * @param listener XMLListener to add.
     public void addXMLEventListener(final XMLListener listener) {
        if (listener != null) {
            listeners.add(listener);
    }//addXMLEventListener()
     * Parse current XML document. Registered XMLEventListeners will receive events during parsing.
     * @param fileName Name of file to read XML content from.
     * @throws Exception
    public void parse(final String fileName) throws Exception {
        if (fileName != null) {
            parse(IOUtils.openInputStream(fileName));
    }//readXML()
      * Parse current XML document. Registered XMLEventListeners will receive events during parsing.
     * @param inputStream InputStream to read XML content from.
      * @throws Exception
     public void parse(final InputStream inputStream) throws Exception {
        if (inputStream != null) {
            xmlReader.parse(new InputSource(inputStream));
    }//readXML()
     * Overwrite super.
     * Receive notification of the beginning of the document.
    @Override
    public void startDocument() {
        for (XMLListener l : listeners) {
            l.documentStarted();
    }//startDocument()
     * Overwrites super.
     * Receive notification of the start of an element.
    @Override
    public void startElement(final String uri, final String localName, final String qName, final Attributes atts) {
        elementStack.push(qName);
        for (XMLListener l : listeners) {
            l.elementStarted(qName, elementStack);
        elementValue = new StringBuilder(); //element value
        //element attributes:
        if (atts.getLength() > 0) {
            String attName = null;
            for (int i = 0; i < atts.getLength(); i++) {
                attName = atts.getQName(i);
                final String attValue = atts.getValue(i);
                for (XMLListener l : listeners) {
                    l.attributeRead(qName, attName, attValue);
            }//next attribute
        }//else: no attributes
    }//startElement()
     * Overwrites super.
     * Receive notification of character data inside an element. This method can be called multiple times
     * from SAX, so we need to append all results of all calls to the final element value.
    @Override
    public void characters(final char ch[], final int start, final int length) {
        String s = new String(ch, start, length);
        elementValue.append(s);
    }//characters()
     * Overwrites super.
     * Receive notification of the end of an element.
    @Override
    public void endElement(final String uri, final String localName, final String qName) {
        for (XMLListener l : listeners) {
            l.elementEnded(qName, elementValue.toString());
        elementStack.pop();
    }//endElement()
     * Overwrite super.
     * Receive notification of the end of the document.
    @Override
    public void endDocument() {
        for (XMLListener l : listeners) {
            l.documentEnded();
    }//endDocument()
}//XMLHandler