Base64 in wsdl maps to java as byte[] . So convert the Document to a
string and then to bytes:

public static final String getDocumentAsString(Document document)
       throws XMLHelperException {
       try {
           // Create source and result objects
           Source source = new DOMSource(document);
           StringWriter out = new StringWriter();
           Result result = new StreamResult(out);
           TransformerFactory tFactory =
TransformerFactory.newInstance();
           Transformer transformer = tFactory.newTransformer();
           transformer.transform(source, result);
           return out.toString();
       } catch (Exception ex) {
           throw new XMLHelperException("XML Document to String
Error", ex);
       }
   }

Just place in a line:

out.toString().getBytes(); and change the return type to byte[] .

Re-reading your post I think you may need to do the reverse - byte[] to
document. That would be:

new String (out.toString().getBytes());

IOW, create a new string with the byte array. Then:

public static final Document getDocument(String xmlString)
       throws XMLHelperException {
       try {
           String nstr = null;
           //cannot have whitespace in the beginning of an xml
document
           if (xmlString.charAt(0) != ' ') {
               nstr = removeInitialWS(xmlString);
           } else {
               nstr = xmlString;
           }

           DocumentBuilderFactory factory =
               DocumentBuilderFactory.newInstance();
           factory.setNamespaceAware(true);
           factory.setIgnoringElementContentWhitespace(false);
           DocumentBuilder builder = factory.newDocumentBuilder();

           InputSource isXml = new InputSource(new
StringReader(nstr));
           return builder.parse(isXml);
       } catch (Exception ex) {
           throw new XMLHelperException("String to XML Document Error
for "
                 + "String:\n\n " + xmlString + " ", ex);
       }
   }

HTH,
iksrazal
http://www.braziloutsource.com/

Either you base64 code it, specify it as a XMLString type or you can use
a CDATA enclosement. I prefer the latter one is it will not create any
more problems, which the others possibly can do.

Tip:
XMLString will become a much larger string than CDATA because everything
that is xml syntax must be escaped.

/tom