How can we parse the DOCTYPE information using XMLEventReader?

Question

I have some existing code which parses the top-level element namespace to determine what kind of XML file we're looking at.

XMLEventReader reader = createXMLEventReader(...);
try {
    while (reader.hasNext()) {
        XMLEvent event = reader.nextEvent();
        switch (event.getEventType()) {
            case XMLStreamConstants.DTD:
                // No particularly useful information here?
                //((DTD) event).getDocumentTypeDeclaraion();
                break;

            case XMLStreamConstants.START_ELEMENT:
                formatInfo.qName = ((StartElement) event).getName();
                return formatInfo;

            default:
                break;
        }
    }
} finally {
    reader.close();
}

If I allow the parser to load DTDs from the web, getDocumentTypeDeclaraion() contains a gigantic string with way more information than I know how to deal with, as it inserts all related DTDs into the string before handing it over. On the other hand, if I block the parser loading DTDs from the web (which is preferable anyway, for obvious reasons), it only gives me the string, "<!DOCTYPE".

Is there no way to get back the values inside the DOCTYPE?

I'm using the default parser which ships with the JRE, in case that matters.

Answer 1

I know it's an old post but I couldn't find an answer on the Web until I've found your question which pointed me in the right direction.

Here the external unparsed entities for a DTD are retrieved by switching on the value given by the XMLEvent#getEventType() method.

XMLInputFactory factory = XMLInputFactory.newInstance();
factory.setXMLResolver(new XMLResolver() {
    @Override
    public Object resolveEntity(String publicID, String systemID,
            String baseURI, String namespace) throws XMLStreamException {
        //return a closed input stream if external entities are not needed
        return new InputStream() {
            @Override
            public int read() throws IOException {
                return -1;
            }
        };
    }
});

XMLEventReader reader = factory.createXMLEventReader( . . . );
try {
    while(reader.hasNext()) {
        XMLEvent event = reader.nextEvent();
        switch (event.getEventType()) {
            case XMLStreamConstants.DTD:
                List<EntityDeclaration> entities = ((DTD)event).getEntities();
                if (entities != null) {
                    for (EntityDeclaration entity : entities)
                        System.out.println(entity.getName() + " = " + entity.getSystemId());
                }
                break;
            case . . .
        }
    }
} finally {
    reader.close();
}