[xsde-users] Extract remaining subtree

[Boris Kolpackov]

Hi Markus,

Markus Kohler <MarkusK at microsol.ie> writes:

> given a XML file and using the embedded parser xsde can I retrieve a 
> certain part of the XML tree as string. Example:
> 
> <somexml>
> 	<somelement>
> 	         <subtree>
> 	               <I>
>                             <want/>
> 			   <this/>
>                            <subtree-as-string/>
>                      </I>
>                   </subtree>
>          </someelement>
> </somexml>

The easiest way would be to override the low-level XML parsing 
callbacks and re-serialize the XML fragment to string, something
along these lines:

class someelement_pimpl: public someelement_pskel
{
public:
   virtual void
   pre ()
   {
     str_.clear ();
   }

   virtual void
   _start_element (const xml_schema::ro_string& ns,
                   const xml_schema::ro_string& name)
   {
     str_ += "<";
     str_ += name;
     open_ = true;
   }

   virtual void
   _end_element (const xml_schema::ro_string& ns,
                 const xml_schema::ro_string& name)
   {
     if (open_)
     {
       str_ += "/>";
       open_ = false;
     }
     else
     {
       str_ += "</";
       str_ += name;
       str_ += ">";
     }
   }   

   virtual void
   _attribute (const xml_schema::ro_string& ns,
               const xml_schema::ro_string& name,
               const xml_schema::ro_string& value)
   {
     str_ += " ";
     str_ += name;
     str_ += " = \"";
     str_ += value;
     str_ += "\"";
   }

   virtual void
   _characters (const xml_schema::ro_string& s)
   {
     if (open_)
     {
       str_ += ">";
       open_ = false;
     }

     str_ += s;
   }

   virtual void
   post_someelement ()
   {
     // fragment is in str_
   }

private:
  bool open_;
  string str_;
};

Note that this will only work for simple XML which doesn't contain
special characters that need escaping. If you need a more robust
solution then you can use the underlying XML serializer that is
used in the C++/Serializer mapping. See libxsde/xsde/c/genx/ for
more information.


Boris