How to read XML file in Delphi?

Question

Here is the thing I want to do. My program is working fine with this:

XMLText =  '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' +
'<book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">' +
  '<title>Harry Potter</title>' +
  '<author>J. K. Rowling.</author>' +
  '<length>400</length>' +
'</book>';


procedure TForm1.Button1Click(Sender: TObject);
var
XMLDoc: IXMLDOMDocument;
Node, SibNode: IXMLDOMNode;
begin
  Memo1.Clear;
  XMLDoc := CoDOMDocument.Create;
  XMLDoc.loadXML(XMLText);
end;

Now I want to import XML file with 6000 books (books.xml) from the same folder where project is, instead of const XMLText. How can I do that?

Thank you! :)

Answer 1

Option 1: load directly from disk

IXMLDomDocument has a load method that accepts a filename. You can use that method instead of loadXML, which you are currently using.

Option 2: load the file into a string first

Alternatively, you can load your file into a string first. I can hardly find any reason to do so in this case, but it can never hurt to know. :)

Take a look at TStringStream, which has a LoadFromFile method to load a file from disk. You can use it to load the entire books.xml into memory. After loading the file, you can pass the stringstreams's DataString property to the loadXML method. This property returns the entire contents of the stream (containing the XML) as a string.

Answer 2

Use the Delphi XML Data Binding Wizard for this.

It will generate a unit with Delphi wrapper objects around your XML file (or if you have it an XSD file describing the XML).

Those wrappers are based on the IXMLDocument which is very similar to the IXMLDOMDocument you are using now, and add a layer around it that allows you to access your data with more support from the Delphi compiler usually making the process of handling the data inside the XML much easier than using plain IXMLDocument or IXMLDOMDocument.

The unit contains methods to load the XML from either a file or a string.

There is a good tutorial and a nice video on using this wizard.

Answer 3

Just change the loadXML to load('YourFileName.xml'):

procedure TForm1.Button1Click(Sender: TObject);
var
  XMLDoc: IXMLDOMDocument;
begin
  XMLDoc := CoDOMDocument.Create;
  XMLDoc.load('MyBooks.xml');
  Memo1.Lines.Text := XMLDoc.xml;
end;