Installation and Usage of TXmlScanner in Borland C++Builder

By Rajeev Rajan (Qualcomm Inc, USA)

Version: Borland C++ Builder ver 5 (BCB5) Integrated Development Environment (IDE).

Installation

• In the BCB5 IDE, I selected the Component | Install Component menu option, and then the "Into new package" tab.
• I browsed the "Unit files" and selected the "LibXmlComps.pas" and "LibXmlParser.pas" files (which are the Pascal component files for the TXmlScanner component)
• I then supplied a new name for the package, which will contain the component.
• The BCB IDE, then comes up with a message like "Creating and Installing Package". If successful, you should now see the "XmlScanner" component in it's own XML tab, in the BCB IDE's component palette.

Compilation problems

• In the LibXmlComps.hpp file, the TExternalEvent property (on line 131), doesn't get properly resolved, and the compiler complains about an improper type name of something.
  (I just commented this line. I did not pursue it further. What the comment does is that even if a call-back is associated with the "OnLoadExternal" property in the BCB's Object Inspector, for the TXmlScanner object, it won't be called.)
  [This was fixed with the release of 2001-02-28. Please inform me if you still have problems. Stefan Heymann]
• There are also some overloading ambiguities between a few elements of the TXmlScanner and the TXmlParser classes, like:
  typedef TAttrList TAttrList;
  and TXmlParser* usage.
  (I just changed the name of the first typedef, and qualified the TXmlParser* with Libxmlparser::TXmlParser.)

Due to paucity of time, I haven't pursued the above problems further, but just hacked around them. I guess I will pursue them, when the need arises or something fishy happens. If someone else does before me, please let me know the solutions. :-)

Usage

Usage of the TXmlScanner object

• Drop the XmlScanner into your form.
• Associate your application code with the various event call-backs. (For example : OnContent, OnEndTag etc.)
• Use the parser as follows:
  For example: If xmlScanner is the name of your TXmlScanner object.

  //-- Load the input xml file, and call execute.
  xmlScanner->LoadFromFile("c:\\myfile.xml");
  xmlScanner->Execute();

• That's it, as your file is parsed, your various event call-back functions will be automatically called.

Usage of the TXmlParser object from TXmlScanner

If you want to use the TXmlParser component from within TXmlScanner, a pointer to the same is available in the TXmlScanner object. I've given some sample code below on how to use it.

For example:
If XmlScanner1 is the name of your TXmlScanner object:

  //-- Load the input xml file..
  XmlScanner1->LoadFromFile("c:\\myfile.xml");

  //-- Init the scanning.
  XmlScanner1->XmlParser->StartScan();

  //-- Loop thru the file for each item.
  AnsiString s;
  while (XmlScanner1->XmlParser->Scan())
  {
     switch (XmlScanner1->XmlParser->CurPartType)
     {
        case  ptStartTag :      //-- Got Start tag.
          s = XmlScanner1->XmlParser->CurName;
          break;

        case  ptContent :       //-- Got content.
          s = XmlScanner1->XmlParser->CurContent;
          break;

        //-- Add other cases here as required..

        default :
          break;
     }
  }

2000-07-27 Rajeev Rajan
2001-02-28 Stefan Heymann: Added a note on the OnLoadExternal problem