SOAPHeaderElement securityHeader = (SOAPHeaderElement) iterator.next();
iterator = securityHeader.getChildElements(new QName("http://www.w3.org/2000/09/xmldsig#", "Signature"));
assertTrue("No signature header", iterator.hasNext());
ByteArrayOutputStream bos = new ByteArrayOutputStream();
message.writeTo(bos);
MimeHeaders mimeHeaders = new MimeHeaders();
mimeHeaders.addHeader("Content-Type", "text/xml");
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());