I found it is possible to do such a thing using the
javax.xml.validation package of Java 1.5:

private class ValidationErrorHandler extends DefaultHandler {
   private List exList = new ArrayList();
   public SAXParseException getFirstSaxParseException() {
       return
(exList.size()==0?null:(SAXParseException)exList.get(0));
   }
   public boolean validationError() {
       return (exList.size()> 0);
   }
   public void error(SAXParseException exception) throws SAXException
{
       exList.add(exception);
   }
   public void fatalError(SAXParseException exception) throws
SAXException {
       exList.add(exception);
   }
   public void warning(SAXParseException exception) throws
SAXException {
   }
}

public void validateDocument(Document doc, String xsd) throws
SAXException, IOException {
   SchemaFactory factory = SchemaFactory.newInstance

(XMLConstants.W3C_XML_SCHEMA_NS_URI);
   Source schemaFile = new StreamSource(new File(xsd));
   Schema schema = factory.newSchema(schemaFile);
   Validator validator = schema.newValidator();
   ValidationErrorHandler errHandler = new ValidationErrorHandler();
   validator.setErrorHandler(errHandler);
   validator.validate(new DOMSource(doc));
   if (errHandler.validationError()) {
       throw errHandler.getFirstSaxParseException();
   }
}