Parse xml response from PL/SQL

Question

Can anyone please help me parse the xml below?
DECLARE
   l_response     CLOB;
   g_system_id    VARCHAR2 (255);
   g_session_id   VARCHAR2 (255);
   g_user_id      VARCHAR2 (255);
BEGIN
   l_response :=
      '--uuid:18cb22a2-11cc-43f4-bfea-c213da179d30+id=156
Content-ID: <http://tempuri.org/0>
Content-Transfer-Encoding: 8bit
Content-Type: application/xop+xml;charset=utf-8;type="application/soap+xml"
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing"><s:Header><a:Action s:mustUnderstand="1">http://tempuri.org/ILoginService/LoginByUserNameResponse</a:Action><a:RelatesTo>urn:uuid:cf410a05-23d4-4b92-a22c-329cbc19fbe7</a:RelatesTo></s:Header><s:Body><LoginByUserNameResponse xmlns="http://tempuri.org/"><LoginByUserNameResult xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:x="http://www.w3.org/2001/XMLSchema"><XObject.m_element i:type="x:string" xmlns="">&lt;OnlineContext SystemId="{19E0DDB4-5FA5-41EE-B624-AEA762865A6C}" SessionId="{F23D32A4-B325-4BFA-9E90-39CA253E843C}" UserId="{2C6ABE4C-D356-46F0-B4BE-9C4F0A36A522}" /&gt;</XObject.m_element></LoginByUserNameResult></LoginByUserNameResponse></s:Body></s:Envelope>
--uuid:18cb22a2-11cc-43f4-bfea-c213da179d30+id=156--';
      SELECT systemid, sessionid, userid
        INTO g_session_id, g_system_id, g_user_id
        FROM XMLTABLE (
                xmlnamespaces ('http://www.w3.org/2003/05/soap-envelope' AS "data"),
                'data:LoginByUserNameResponse/LoginByUserNameResult/XObject.m_element/OnlineContext'
                PASSING xmltype (l_response)
                COLUMNS systemid VARCHAR2 (50) PATH '@OnlineContext',
                        sessionid VARCHAR2 (50) PATH '@OnlineContext',
                        userid VARCHAR2 (50) PATH '@OnlineContext') xt;
   DBMS_OUTPUT.put_line (
         'Session id '
      || g_session_id
      || ' System id '
      || g_system_id
      || ' User id '
      || g_user_id);
END;
Thanks.

Answer 1

This gets you a little bit closer
declare 
-- Local variables here
l_response     CLOB;
g_system_id    VARCHAR2 (255);
g_session_id   VARCHAR2 (255);
g_user_id      VARCHAR2 (255);
begin
-- Test statements here
l_response := '<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing"> 
<s:Header>
    <a:Action s:mustUnderstand="1">http://tempuri.org/ILoginService/LoginByUserNameResponse</a:Action> 
    <a:RelatesTo>urn:uuid:cf410a05-23d4-4b92-a22c-329cbc19fbe7</a:RelatesTo>
</s:Header>
<s:Body>
    <LoginByUserNameResponse xmlns="http://tempuri.org/"> 
       <LoginByUserNameResult xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:x="http://www.w3.org/2001/XMLSchema"> 
          <XObject.m_element i:type="x:string" xmlns=""><OnlineContext SystemId="{19E0DDB4-5FA5-41EE-B624-AEA762865A6C}" SessionId="{F23D32A4-B325-4BFA-9E90-39CA253E843C}" UserId="{2C6ABE4C-D356-46F0-B4BE-9C4F0A36A522}" /></XObject.m_element>
          </LoginByUserNameResult>
      </LoginByUserNameResponse>
  </s:Body>
</s:Envelope>';
    SELECT systemid, sessionid, userid
      INTO g_session_id, g_system_id, g_user_id
      FROM XMLTABLE (
              xmlnamespaces ('http://www.w3.org/2003/05/soap-envelope' AS "s", 
                             'http://tempuri.org/' as "data"), 
              's:Envelope/s:Body/data:LoginByUserNameResponse/data:LoginByUserNameResult/XObject.m_element/OnlineContext'
              PASSING xmltype (l_response)
              COLUMNS systemid VARCHAR2 (50) PATH '@SystemId',
                      sessionid VARCHAR2 (50) PATH '@SessionId',
                      userid VARCHAR2 (50) PATH '@UserId') xt;
DBMS_OUTPUT.put_line (
       'Session id '
    || g_session_id
    || ' System id '
    || g_system_id
    || ' User id '
    || g_user_id);
end;    
You will need to manually parse that CLOB and pull out the XML string itself from the response.  That can be done via SUBSTR and INSTR looking for the first < and last > in what you showed at least.  Updated from previous version to work properly with the xmlns="", which resets the default namespace back to the default value.  The XPath was corrected to reflect proper prefix usage.