Xerces DOM parser incredibly slow?

Currently, I am trying to clean up an HTML file using JTidy, convert it to XHTML and provide the results to a DOM parser. The following code is the result of these efforts:

public class HeaderBasedNewsProvider implements INewsProvider {

    /* ... */

    public Collection<INewsEntry> getNewsEntries() throws NewsUnavailableException {
            Document document;
        try {
            document = getCleanedDocument();
        } catch (Exception e) {
            throw new NewsUnavailableException(e);
        }
        System.err.println(document.getDocumentElement().getTextContent());
        return null;
    }

    private final Document getCleanedDocument() throws IOException, SAXException, ParserConfigurationException {
        InputStream input = inputStreamProvider.getInputStream();
        Tidy tidy = new Tidy();
        tidy.setXHTML(true);
        ByteArrayOutputStream tidyOutputStream = new ByteArrayOutputStream();
        tidy.parse(input, tidyOutputStream);
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        factory.setValidating(false);
        InputStream domInputStream = new ByteArrayInputStream(tidyOutputStream.toByteArray());
        System.err.println(factory.getClass());
        return factory.newDocumentBuilder().parse(domInputStream);
    }
}

However, the DOM parser implementation (com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl) on my system seems to be incredibly slow. Even for one-line documents such as the following, parsing takes 2-3 minutes:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title></title></head><body><div class="text"><h2>Nachricht vom 16. Juni 2011</h2><h1>Titel</h1><p>Mitteilung <a href="dokumente/medienmitteilungen/MM_NR_jglp.pdf" target="_blank">weiter</a> mehr Mitteilung</p></div></body></html>

Note that - in contrast to the DOM parser - JTidy finishes its work within a second. Therefore, I suspect that I'm somehow misusing the DOM API.

Thanks in advance for any suggestions on this one!

回答1:

Even when not validating, a XML parser needs to fetch the DTD, for example to support named character entities. You should look into implementing an EntityResolver that resolves the request for the DTD to a local copy.

回答2:

HTML dtd's are huge, using includes. They take forever. Use an XML catalog. There one can store the dtds locally and map them by their system ID.

If you use a tool, like maven, you will find sufficient pointers.

The advantage i.o. intercepting entities as the accepted answer suggests, is that you receive the correct characters.