Validate XML against DTD? XSD OK. SSCCE.

"Andrew Thompson" <u32984@uwe>
Wed, 03 Oct 2007 12:25:35 GMT
This example* shows how to validate XML against XSD.

What I would *like* to do is also offer validation
against DTD. Unforutnately, when the 'DTD' XMLConstant
is selected in the last dialog (bottom option, I get the output..

"Create schema from ''.
Exception in thread "main" java.lang.IllegalArgumentException:
No SchemaFactory that implements the schema language specified by: could be loaded
  at javax.xml.validation.SchemaFactory

Does anybody demonstrate how to validate against DTD?

BTW - A quick search on ..
..did not reveal 'much', so I am thinking I
have 'got this all wrong'.


import javax.swing.JOptionPane;
import javax.swing.JComboBox;

import javax.xml.XMLConstants;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Schema;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;

import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

import org.w3c.dom.Document;

/** Simple example of validating a structured document (XML)
against a schema (XSD).
Can anybody change this to code that will successfully
validate against a DTD? */
class XMLValidate {

  public static void main(String[] args) throws

    String[] contentOptions =
      // The Player JNLP is meant to pop the Java Control Panel
      // It was never intended to be valid accoring to the spec.,
      // as such, it is a good 'target' for validation, as it will
      // most likely remain 'invalid' according to the DTD/XSD
      // Sun's Java2D Demo - valid at time of check
      // example of loading file from same directory

    String content = null;

    String[] definitionOptions =
      // the XSD from the PhySci site
      // DTD for the Sun JNLP format
      // **can we create a schema from this?**
      // for access from local file-system

    String definition = null;

    String[] languageOptions =
      // XML
      // RelaxNG
      // XPath
      // DTD
      // No SchemaFactory that implements the schema language ..
    String language = null;

    XMLErrorHandler errorHandler = new XMLErrorHandler();

    if (args.length==2) {
      content = args[0];
      definition = args[1];
    } else if (args.length==0) {
      JComboBox contentChoice = new JComboBox (contentOptions);
        "XML URL (document)",
      content = (String)contentChoice.getSelectedItem();

      JComboBox definitionChoice = new JComboBox (definitionOptions);
        "XSD(/DTD) URL (schema definition)",
      definition = (String)definitionChoice.getSelectedItem();

      JComboBox languageChoice = new JComboBox (languageOptions);
        "Language - see XMLConstants",
      language = (String)languageChoice.getSelectedItem();
    } else {
        "Usage: java XMLValidate "+
        "file:./the.xml file:./the.xsd XMLConstants.languages");
        "Usage: java XMLValidate (will prompt for params)");
    DocumentBuilderFactory factory =
    factory.setFeature("", true);
true) ;

    System.out.println("Create schema from '" + definition + "'.");
    SchemaFactory schemaFactory = SchemaFactory.newInstance(language);
    Schema schema = schemaFactory.newSchema( new StreamSource(definition) );
    factory.setSchema( schema );
    System.out.println("Schema created successfully.");

    DocumentBuilder documentBuilder = factory.newDocumentBuilder();
    documentBuilder.setErrorHandler( errorHandler );

    System.out.println("Validate content from '" +
      content +
      "' against schema.");
    try {
      Document document = documentBuilder.parse( content );
    } catch (SAXException e) {
      System.err.println( e.getMessage() );
      System.err.println( "Validation failed.." );
      "Total (warning, error, fatal) errors detected: " +
      errorHandler.getErrorCount() );

class XMLErrorHandler extends DefaultHandler {

  private int errorCount=0;

    public void warning(SAXParseException exception)
      throws SAXException {

    public void error(SAXParseException exception)
      throws SAXException {

    public void fatalError(SAXParseException exception)
      throws SAXException {

    public void processException(SAXParseException exception) {

    public int getErrorCount() {
    return errorCount;

Andrew Thompson

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