Using dbms_xmlgen.convert to capture URL

Question

I am using a web service that returns XML response (see result below). I need to capture the URL in the 'GetIEPUrlWithAuditResult' tag. I tried this code but get a ORA-30625: method dispatch on NULL SELF argument is disallowed. Is my dbms_xmlgen.convert path to the tag correct?
l_xml := xmltype.createxml(l_clob);
l_val := dbms_xmlgen.convert(l_xml.extract('//GetIEPUrlWithAuditResult/text()').getclobval(),1);
RESULT
<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><GetIEPUrlWithAuditResponse xmlns="http://www.iepdirect.com/CentrisWebServices/IEPViwer"><GetIEPUrlWithAuditResult>https://www.iepdirect.com/lettersandreports/maintenance/iepviewer.aspx?auditinfo=TEST&amp;viewertoken=cn097c5e6c69a94fbc9dffcd70bd88f2b9|||d0Gpyh6ZEelbL6lMz+ZDWBTyMqsfjkDFPlat6T+8vMQ=</GetIEPUrlWithAuditResult></GetIEPUrlWithAuditResponse></soap:Body></soap:Envelope>

Answer 1

Is my dbms_xmlgen.convert path to the tag correct?Half correct.
You're missing the namespace mapping, and you'll need to add the text() node to the XPath expression in order to retrieve the value instead of the whole element.
l_val := dbms_xmlgen.convert(
            l_xml.extract(
              '//GetIEPUrlWithAuditResult/text()'
            , 'xmlns="http://www.iepdirect.com/CentrisWebServices/IEPViwer"'
            ).getstringval()
          , 1
          );But, in this case, it's better to use extractValue (as it performs the necessary conversions for us) :
select extractvalue(
          l_xml
        , '//GetIEPUrlWithAuditResult'
        , 'xmlns="http://www.iepdirect.com/CentrisWebServices/IEPViwer"'
into l_val
from dual;