Если DTD не указан в файле XML, вы можете использовать Transformer, чтобы добавить его и затем проанализировать, как показано ниже:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder db = factory.newDocumentBuilder();
//parse file into DOM
Document doc = db.parse(new File("file.xml"));
DOMSource source = new DOMSource(doc);
//now use a transformer to add the DTD element
TransformerFactory tf = TransformerFactory.newInstance();
Transformer transformer = tf.newTransformer();
transformer.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, "/path/to/file.dtd");
StringWriter writer = new StringWriter();
StreamResult result = new StreamResult(writer);
transformer.transform(source, result);
//finally parse the result.
//this will throw an exception if the doc is invalid
db.parse(new InputSource(new StringReader(writer.toString())));