Problem reading from XMLDoc

[RedOctober]

PLATFORM:

Lazarus 1.8.4, indyHTTP 10.6.2.0, OS: Windows Server 2016 (latest updates)

BACKGROUND:

I am converting an old Delphi XE3 project to Lazarus.  The Delphi XE3 project is able to get XML data from Data 24/7 and CDyne via HTTPS using Indy.  All works correctly.

PROBLEM:

I am unable to read specific nodes.  For example, I want to read the value of the "status" node.  Can't do it.

I am following the example here: https://wiki.freepascal.org/XML_Tutorial
I have loaded the XMLDoc as follows:  (Assume all try..excepts and try..finally 's and .Free 's are in place)

Code: Pascal  [Select][+][-]

1.  
2. uses
3.     Classes, SysUtils, StdCtrls, Forms, Controls,
4.     idHTTP, idSSLOpenSSL, idURI,
5.     DOM, laz2_DOM, laz2_XMLRead, laz2_XMLWrite, laz2_XMLCfg, laz2_XMLUtils, XMLStreaming, ...;
6.  
7.  
8.  
9. var
10.   XMLNode: TDOMNode;
11.   XMLDoc: TXMLDocument;
12.   xml_mem_strm: TMemoryStream;  
13.   str_strm: TStringStream;
14.  
15. begin
16. ...
17.     xml_mem_strm := TMemoryStream.Create;
18.     str_strm := TStringStream.Create('');
19. ...
20.    xHTTP.Get(GlobalVars.TxtMsg.https_get_cmd, xml_mem_strm);
21.    xml_mem_strm.Position := 0;
22.  
23.    ReadXMLFile(XMLDoc, xml_mem_strm);
24.  
25.  

This line converts the memory stream to a string and reveals that ALL the data EXISTS in the returned memory stream.

Code: Pascal  [Select][+][-]

1.     prc_log.Lines.Add(MemoryStreamToString(xml_mem_strm));
2.  

The resulting string from the above line is:

Code: Pascal  [Select][+][-]

1. <?xml version="1.0"?><response><results><result item="1"><status>OK</status><number>15555555555</number><wless>n</wless><carrier_name>Telus Communications, Inc.</carrier_name><carrier_id>50106</carrier_id><sms_address> </sms_address><mms_address> </mms_address></result></results></response>
2.  

HERE IS WHAT I HAVE TRIED:

Code: Pascal  [Select][+][-]

1.  
2.     // Status Node  Attempt 1  - Fails
3.     idx := prc_log.Lines.Add('Selecting Status Node...');
4.     Application.ProcessMessages;
5.     XMLNode := XMLDoc.DocumentElement.FindNode('results/result(item=1)/status');  
6.     if not Assigned(XMLNode) then
7.       begin
8.         prc_log.Lines[idx] := prc_log.Lines[idx] + 'Can''t find it. Exiting now.';
9.         snd_err := True;
10.         Application.ProcessMessages;
11.         Exit;
12.       end;
13.     GlobalVars.TxtMsg.xml_status := XMLNode.FirstChild.NodeValue;
14.     prc_log.Lines[idx] := prc_log.Lines[idx] + 'Got it: '  + GlobalVars.TxtMsg.xml_status;
15.     Application.ProcessMessages;
16.  
17.     // Status Node  Attempt 2 - Fails
18.     idx := prc_log.Lines.Add('Selecting Status Node...');
19.     Application.ProcessMessages;
20.     XMLNode := XMLDoc.DocumentElement.FindNode('/response/results/result[@item=''1'']/status');    
21.     if not Assigned(XMLNode) then
22.       begin
23.         prc_log.Lines[idx] := prc_log.Lines[idx] + 'Can''t find it. Exiting now.';
24.         snd_err := True;
25.         Application.ProcessMessages;
26.         Exit;
27.       end;
28.     GlobalVars.TxtMsg.xml_status := XMLNode.FirstChild.NodeValue;
29.     prc_log.Lines[idx] := prc_log.Lines[idx] + 'Got it: '  + GlobalVars.TxtMsg.xml_status;
30.     Application.ProcessMessages;
31.  
32.     // Status Node  Attempt 3 - Fails
33.     idx := prc_log.Lines.Add('Selecting Status Node...');
34.     Application.ProcessMessages;
35.     XMLNode := XMLDoc.DocumentElement.FindNode('status');    
36.     if not Assigned(XMLNode) then
37.       begin
38.         prc_log.Lines[idx] := prc_log.Lines[idx] + 'Can''t find it. Exiting now.';
39.         snd_err := True;
40.         Application.ProcessMessages;
41.         Exit;
42.       end;
43.     GlobalVars.TxtMsg.xml_status := XMLNode.FirstChild.NodeValue;
44.     prc_log.Lines[idx] := prc_log.Lines[idx] + 'Got it: '  + GlobalVars.TxtMsg.xml_status;
45.     Application.ProcessMessages;
46.  
47.  

MY QUESTION:

What is the proper syntax to pull out the various node values, by using their node name, from the XML in the XMLDoc?

Thanks in advance.

[wp]

FindNode does not search recursively, only the direct children of a node. But you can easily extend it (there are probably better ways, but this one came to my mind first):

Code: Pascal  [Select][+][-]

1. var
2.   path: String;       // path of nodes, e.g. "ProjectOptions/BuildModes/Item1"
3.   sa: TStringArray;
4.   node: TDOMNode;
5.   i: Integer;
6. ...
7.   sa := path.Split('/');  
8.   node := doc.DocumentElement;
9.   i := 0;
10.   while (node <> nil) and (i < Length(sa)) do
11.   begin
12.     node := node.FindNode(sa[i]);
13.     inc(i);
14.   end;
15.   if node <> nil then
16.   begin
17.      // found...

[RedOctober]

Hi wp,

I have downloaded your example and it works.  However, I am now stuck trying to figure out the syntax for my "Telco" xml file using your example. Here is the xml structure:

Code: Pascal  [Select][+][-]

1. <?xml version="1.0"?>
2. <response>
3.   <results>
4.     <result item="1">
5.       <status>OK</status>
6.       <number>15555555555</number>
7.       <wless>n</wless>
8.       <carrier_name>Telus Communications, Inc.</carrier_name>
9.       <carrier_id>50106</carrier_id>
10.       <sms_address> </sms_address>
11.       <mms_address> </mms_address>
12.     </result>
13.   </results>
14. </response>

Here is what I have tried, none of these returns the status value, which should be "OK".  I just get "NOT FOUND'

response/results/result/status
response/results/result[@item=''1'']/status
response/results/result item=''1"/status
response/results/result/status

What is the correct syntax to use, to get the "OK" from the status node?

Thanks in advance.

[dsiders]

Here is what I have tried, none of these returns the status value, which should be "OK".  I just get "NOT FOUND'

response/results/result/status
response/results/result[@item=''1'']/status
response/results/result item=''1"/status
response/results/result/status

What is the correct syntax to use, to get the "OK" from the status node?

Thanks in advance.

Those are XPath expressions, so you can use:

/response/results/result[@item="1"]/status[text()] or
/response/results/result[1]/status[text()]

[RedOctober]

Hmmm.. neither of these work ....

[bytebites]

Hi wp,

I have downloaded your example and it works.  However, I am now stuck trying to figure out the syntax for my "Telco" xml file using your example. Here is the xml structure:

Code: Pascal  [Select][+][-]

1. <?xml version="1.0"?>
2. <response>
3.   <results>
4.     <result item="1">
5.       <status>OK</status>
6.       <number>15555555555</number>
7.       <wless>n</wless>
8.       <carrier_name>Telus Communications, Inc.</carrier_name>
9.       <carrier_id>50106</carrier_id>
10.       <sms_address> </sms_address>
11.       <mms_address> </mms_address>
12.     </result>
13.   </results>
14. </response>

Here is what I have tried, none of these returns the status value, which should be "OK".  I just get "NOT FOUND'

response/results/result/status
response/results/result[@item=''1'']/status
response/results/result item=''1"/status
response/results/result/status

What is the correct syntax to use, to get the "OK" from the status node?

Thanks in advance.

Try without root: results/result/status

[RedOctober]

Works now.  Since the status node has no attributes and I just wanted the text, I used:   

Code: Pascal  [Select][+][-]

1.   Listbox1.Items.Add(XMLNode.TextContent);
2.  

to display the text "OK".  Thanks for your detailed help on this.  Project is back on track now.

[wp]

Sorry, I did not see the xml sample of your first post.

Glad that it works now. But you will have a problem when there are several "result" nodes with different "item" attributes, e.g.

Code: XML  [Select][+][-]

1. <?xml version="1.0"?>
2. <response>
3.   <results>
4.     <result item="1">
5.       <status>OK</status>
6.     </result>
7.     <result item="2">
8.       <status>OK</status>
9.     </result>
10.   </results>
11. </response>

My code will always return only the first one...

The attached modified version iterates through all child nodes of "results" until it finds the one with the attribute 'item="1"'.

[RedOctober]

I'm working with CDYNE and Data 24/7.  The HTTP requests I make always result in the same output, so your code with my mods will always work.  Thanks for the help.