Question

I am validating an in-memory DOM object using the javax.xml.validation.Validator class against an XSD schema. I am getting a SAXParseException being thrown during the validation whenever there is some data corruption in the information I populate my DOM from.

An example error:

org.xml.SAXParseException: cvc-datatype-valid.1.2.1: ‘???”??[?????G?>???p~tn??~0?1]’ is not a valid valud for ‘hexBinary’.

What I am hoping is that there is a way to find the location of this error in my in-memory DOM and print out the offending element and its parent element. My current code is:

public void writeDocumentToFile(Document document) throws XMLWriteException {
  try {
    // Validate the document against the schema
    Validator validator = getSchema(xmlSchema).newValidator();
    validator.validate(new DOMSource(document));

    // Serialisation logic here.

  } catch(SAXException e) {
    throw new XMLWriteException(e); // This is being thrown
  } // Some other exceptions caught here.
}

private Schema getSchema(URL schema) throws SAXException {
  SchemaFactory schemaFactory = 
    SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

  // Some logic here to specify a ResourceResolver

  return schemaFactory.newSchema(schema);
}

I have looked into the Validator#setErrorHandler(ErrorHandler handler) method but the ErrorHandler interface only gives me exposure to a SAXParseException which only exposes the line number and column number of the error. Because I am using an in-memory DOM this returns -1 for both line and column number.

Is there a better way to do this? I don’t really want to have to manually validate the Strings before I add them to the DOM if the libraries provide me the function I’m looking for.

I’m using JDK 6 update 26 and JDK 6 update 7 depending on where this code is running.

EDIT: With this code added –

validator.setErrorHandler(new ErrorHandler() {
  @Override
  public void warning(SAXParseException exception) throws SAXException {
    printException(exception);
    throw exception;
  }

  @Override
  public void error(SAXParseException exception) throws SAXException {
    printException(exception);
    throw exception;
  }

  @Override
  public void fatalError(SAXParseException exception) throws SAXException {
    printException(exception);
    throw exception;
  }

  private void printException(SAXParseException exception) {
    System.out.println("exception.getPublicId() = " + exception.getPublicId());
    System.out.println("exception.getSystemId() = " + exception.getSystemId());
    System.out.println("exception.getColumnNumber() = " + exception.getColumnNumber());
    System.out.println("exception.getLineNumber() = " + exception.getLineNumber());
  }
});

I get the output:

exception.getPublicId() = null
exception.getSystemId() = null
exception.getColumnNumber() = -1
exception.getLineNumber() = -1

Answer 1

If you are using Xerces (the Sun JDK default), you can get the element that failed validation through the http://apache.org/xml/properties/dom/current-element-node property:

...
catch (SAXParseException e)
{
    Element curElement = (Element)validator.getProperty("http://apache.org/xml/properties/dom/current-element-node");

    System.out.println("Validation error: " + e.getMessage());
    System.out.println("Element: " + curElement);
}   

Example:

String xml = "<root xmlns=\"http://www.myschema.org\">\n" +
             "<text>This is text</text>\n" +
             "<number>32</number>\n" +
             "<number>abc</number>\n" +
             "</root>";

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
Document doc = dbf.newDocumentBuilder().parse(new ByteArrayInputStream(xml.getBytes("UTF-8")));
Schema schema = getSchema(getClass().getResource("myschema.xsd"));

Validator validator = schema.newValidator();
try
{
    validator.validate(new DOMSource(doc));
}
catch (SAXParseException e)
{
    Element curElement = (Element)validator.getProperty("http://apache.org/xml/properties/dom/current-element-node");

    System.out.println("Validation error: " + e.getMessage());
    System.out.println(curElement.getLocalName() + ": " + curElement.getTextContent());

    //Use curElement.getParentNode() or whatever you need here
}         

If you need to get line/column numbers from the DOM, this answer has a solution to that problem.