XML Parsing with Default Namespaces via PL/SQL

In my previous post I covered parsing of XML where a namespace prefix existed for each namespace. What happens when you have to parse XML where some of the XML is in a default namespace? Make up a namespace prefix. No W3C complaint parser will care about what the prefix is in the XML and the prefix in the XPath is as long as the URI (the stuff within the " quotes) is the same for the node in question. Here is a simple example based off the ongoing example

DECLARE
  l_doc       VARCHAR2(2000);
  l_domdoc    dbms_xmldom.DOMDocument;
  l_nodelist  dbms_xmldom.DOMNodeList;
  l_node      dbms_xmldom.DOMNode;
  l_value     VARCHAR2(30);
  l_a_ns      VARCHAR2(30);
  l_both_ns   VARCHAR2(60);

  l_xmltype   XMLTYPE;
  l_empx      XMLTYPE;
  l_index     PLS_INTEGER;
  l_col_ind   PLS_INTEGER;
BEGIN
  l_doc := '<employees xmlns="abc.com/123" xmlns:b="xyz.net/456">
 <emp>
  <name>Scott</name>
  <b:favorites>
   <b:color>red</b:color>
   <b:color>orange</b:color>
  </b:favorites>
 </emp>
 <emp>
  <name>John</name>
  <b:favorites>
   <b:color>blue</b:color>
   <b:color>green</b:color>
  </b:favorites>
 </emp>
</employees>';

  l_a_ns := 'xmlns:a="abc.com/123"';  -- assign random prefix to namespace
  -- assigning a different prefix to this namespace
  l_both_ns := l_a_ns || ' xmlns:c="xyz.net/456"'; -- separated by a space

  l_xmltype := XMLTYPE(l_doc);

  -- Method 4
  dbms_output.new_line;
  dbms_output.put_line('Method 4');
  l_value := l_xmltype.extract('/employees/emp[2]/name/text()', 'xmlns="abc.com/123"').getStringVal();
  dbms_output.put_line('Emp Name: '||l_value);

  -- Method 5
  dbms_output.new_line;
  dbms_output.put_line('Method 5');
  l_index := 1;
  WHILE l_xmltype.Existsnode('/a:employees/a:emp[' || To_Char(l_index) || ']', l_a_ns) > 0
  LOOP
   l_empx := l_xmltype.extract('/a:employees/a:emp[' || To_Char(l_index) || ']', l_a_ns);
   l_col_ind := 1;
   WHILE l_empx.Existsnode('/a:emp/c:favorites/c:color[' || To_Char(l_col_ind) || ']', l_both_ns) > 0
   LOOP
      l_value := l_empx.extract('/a:emp/c:favorites/c:color[' || To_Char(l_col_ind) || ']/text()', l_both_ns).getStringVal();
      dbms_output.put_line('Color: '||l_value);
      l_col_ind := l_col_ind + 1;
   END LOOP;
   l_index := l_index + 1;
  END LOOP;
END;

In the XML, we have a default namespace of "abc.com/123" for the elements and the previous "xyz.net/456" namespace. In the code, I randomly picked a prefix of "a" for the default namespace and so anytime an element in the default namespace is referenced, the corresponding prefix is used.

As Method 4 shows, you could just provide the default namespace as is for the third parm and then there is no need to include a prefix in the XPath itself. I prefer to go the route of method 5 as I have encountered XML where the "default" namespace has changed several nodes deep in the XML. Since the default changes, you need to specify a namespace prefix to keep things in order with the namespace each node resides in.