delphi read xml element

Question

I'm new to XML and we need to do GeoCoding with the new Bing Spatial Data API. I've managed to get a result back from them in xml format. How would I read specific elements in the response, ie. the Link, Status and ErrorMessages?

<?xml version="1.0" encoding="utf-8"?>
<Response xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://schemas.microsoft.com/search/local/ws/rest/v1">
    <Copyright>Copyright © 2011 Microsoft and its suppliers. All rights reserved. This API cannot be accessed and the content and any results may not be used, reproduced or transmitted in any manner without express written permission from Microsoft Corporation.</Copyright>
    <BrandLogoUri>http://spatial.virtualearth.net/Branding/logo_powered_by.png</BrandLogoUri>
    <StatusCode>201</StatusCode>
    <StatusDescription>Created</StatusDescription>
    <AuthenticationResultCode>ValidCredentials</AuthenticationResultCode>
    <TraceId>ID|02.00.82.2300|</TraceId>
    <ResourceSets>
        <ResourceSet>
            <EstimatedTotal>1</EstimatedTotal>
            <Resources>
                <DataflowJob>
                    <Id>ID</Id>
                    <Link role="self">https://spatial.virtualearth.net/REST/v1/dataflows/Geocode/ID</Link>
                    <Status>Pending</Status>
                    <CreatedDate>2011-03-30T08:03:09.3551157-07:00</CreatedDate>
                    <CompletedDate xsi:nil="true" />
                    <TotalEntityCount>0</TotalEntityCount>
                    <ProcessedEntityCount>0</ProcessedEntityCount>
                    <FailedEntityCount>0</FailedEntityCount>
                </DataflowJob>
            </Resources>
        </ResourceSet>
    </ResourceSets>
</Response>

I'm using Delphi XE.

Regards, Pieter

Answer 1

How about using some simple XPATH to get the requested values?

//Link[1]/node() - selects the first "Link" node from the whole document, and then selects the first child node of any kind. It just happens that the first child node is the unnamed node containing the actual https link.

Assuming the XML document is loaded into Doc: TXMLDocument, you can extract the Link with this code:

(Doc.DOMDocument as IDomNodeSelect).selectNode('//Link[1]/node()').nodeValue

You can find some documentation about XPath reading those XPath Examples on MSDN. You might find better documentation at w3schools. And to top it all up, here's a simple (but complete) console application that uses XPath to extract and display the 3 requested values:

program Project14;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Xmldoc,
  xmldom,
  ActiveX;

var X: TXMLDocument;
    Node: IDOMNode;
    Sel: IDomNodeSelect;

begin
  try
    CoInitialize(nil);

    X := TXMLDocument.Create(nil);
    try

      // Load XML from a string constant so I can include the exact XML sample from this
      // question into the code. Note the "SomeNode" node, it's required to make that XML
      // valid.

      X.LoadFromXML(
        '<SomeNode>'+
        '  <Link role="self">' +
        '    https://spatial.virtualearth.net/REST/v1/dataflows/Geocode/jobid' +
        '  </Link>' +
        '  <Status>Aborted</Status>' +
        '  <ErrorMessage>The data uploaded in this request was not valid.</ErrorMessage>' +
        '</SomeNode>'
      );

      // Shortcut: Keep a reference to the IDomNodeSelect interface

      Sel := X.DOMDocument as IDomNodeSelect;

      // Extract and WriteLn() the values. Painfully simple!

      WriteLn(Sel.selectNode('//Link[1]/node()').nodeValue);
      WriteLn(Sel.selectNode('//Status[1]/node()').nodeValue);
      WriteLn(Sel.selectNode('//ErrorMessage[1]/node()').nodeValue);

      ReadLn;
    finally X.Free;
    end;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.