How to import MSXML2_TLB

2017-03-13 15:07  msxml2    [permalink]

O my god I can't believe this isn't somewhere on the net already! I come across this question and ofcourse there's the default discussion about Indy and OpenSSL/LibreSSL, and Arnaud is very (very!) right about proposing to use WinHTTP. I personally would see if I could do it with MSXML2's XMLHTTP object. Contrary to what it looks like, it doesn't really have to do much about XML, and you can do really almost all of what you need out of a HTTP request with open, setRequestHeader, send and responseText or responseStream, with a much more straight-forward syntax. (If you can live with COM.)

Plus there's another pretty sound reason: back in the days, when using WinHTTP and/or VBScript (for the RegExp component...) you would make it very clear it would only work if you got Internet Explorer version 5.5 or newer installed. "How much back was this?" I hear you ask? It depends, but it's so far back that pretty much all of XML things came after, and XML being to closely related to data-processing, Microsoft needed to put MSXML*.dll deeper into the system than its web-browser. If it's tied to the MDAC or the actual core system I'm, not sure, but years of use and the success of AJAX caused it to get very many security updates. I suspect a far bit more than the DLL that handles your WinHTTP calls...

So, without further ado, do as I do and import the "Microsoft XML" type library in the most recent version you can find on your system:

On old Delphi versions (e.g. the venerable version 7) open 'Projects' on the main menu, then 'Import Type Library...', then select "Microsoft XML, v?.0 (Version ?.0)" from the list. Your system may have multiple versions installed, pick the highest version number (in my case 6.0). Uncheck "Generate Component Wrapper" as usually you don't need this, and actually have the added benefit of automatic reference counting when you use interface references to keep track of COM object instances.

On newer Delphi versions, I've noticed the import functionality has centralised, and is now under the 'Components' menu, the 'Import Component...' option and you need to select "Import a Type Library" from the first list, and then search for "Microsoft XML".

This will result in a automatically generated MSXML2_TLB.pas that you otherwise don't need to worry about. Except perhaps include it in all of your projects you'd launch HTTP requests from.
Use the CoXMLHTTP.Create class function to get a new XMLHTTP instance, and it's open and send methods to make magic happen.

uses MSXML2_TLB;
  
procedure TForm1.Button1Click(Sender: TObject);
var
  r:XMLHTTP;
begin
  r:=CoXMLHTTP.Create;
  r.open('GET','http://www.google.com/search?q=hello+world',false,EmptyParam,EmptyParam);
  r.send(EmptyParam);
  Memo1.Text:=r.responseText;
end;

There's more ofcourse. This is just the basics. Depending on what you need to do there's HTTP POST and ways to correctly encode values into the request body you pass to send, using setRequestHeader. And if you need to handle larger chuncks of data, you should check out responseBody and perhaps TOleStream declared in AxCtrls.pas.

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