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Delphi: How to parse an HTML page with XPath?
Hi there!
What I need is an working example that loads an HTML web page (e.g. with TIdHttp) and applies an XPath expression to retrieve a result.
Use for example: http://de.wikipedia.org/wiki/Physik
XPath expression: //*[@id="toc"]/ul/li[2]/ul
The expression should return: Mathematische Physik
Regards,
Dirk.
What I need is an working example that loads an HTML web page (e.g. with TIdHttp) and applies an XPath expression to retrieve a result.
Use for example: http://de.wikipedia.org/wiki/Physik
XPath expression: //*[@id="toc"]/ul/li[2]/ul
The expression should return: Mathematische Physik
Regards,
Dirk.
Asked:
-
4
2
1 Solution
Sorry, I'm not aware of external link agreement until now. Links I posted here was a "fast" help - some users complain about slowness. I'm not encourage giving
So still .... made working example:
Example is using windows MSXML2 interface which you can get here:
MSXML2_TLB.pas
Use XMLHTTPRequest to get http page (instead of TIdHttp) and pass response to my ParseHTM4String function and XPath search string.
Usage:
Line
working example- asker will do copy paste - but what is behind ....
So still .... made working example:
uses ActiveX, MSXML2_TLB;
...
function ParseHTM4String(sTextToParse, sXPath: String; var sResponse: String;
var sError: String): Boolean;
var
XMLDomDoc: IXMLDOMDocument2;
XMLDomNode: IXMLDOMNode;
begin
Result := False;
sResponse := '';
sError := '';
XMLDomDoc := CoDOMDocument30.Create;
try
try
XMLDomDoc.setProperty('ProhibitDTD', 'False');
XMLDomDoc.async := False;
XMLDomDoc.PreserveWhitespace := True;
XMLDomDoc.ResolveExternals := True;
XMLDomDoc.ValidateOnParse := False;
if XMLDomDoc.loadXML(sTextToParse) then
begin
XMLDomDoc.setProperty('SelectionLanguage', 'XPath');
XMLDomDoc.setProperty('SelectionNamespaces', 'xmlns:x=''http://www.w3.org/1999/xhtml''');
XMLDomNode := XMLDomDoc.selectSingleNode(sXPath);
if XMLDomNode<>nil then
begin
sResponse := XMLDomNode.text;
Result := True;
end;
end
else
sError := Trim(XMLDomDoc.parseError.reason);
except
end;
finally
XMLDomDoc := nil;
end;
end;
function GetHTMLInfo(sURI, sXPath: String; var sResponse: String; var sError: String): Boolean;
const
COMPLETED = 4;
OK = 200;
var
XMLHTTPRequest : IXMLHTTPRequest;
begin
Result := False;
sResponse := '';
sError := '';
XMLHTTPRequest := CoXMLHTTP.Create;
try
XMLHTTPRequest.open('GET', sURI, False, EmptyParam, EmptyParam);
XMLHTTPRequest.send(EmptyParam);
if (XMLHTTPRequest.readyState = COMPLETED) and (XMLHTTPRequest.status = OK) then
begin
Result := ParseHTM4String(XMLHTTPRequest.responseText, sXPath, sResponse, sError);
end
else
sError := Trim(XMLHTTPRequest.statusText);
finally
XMLHTTPRequest := nil;
end;
end;
initialization
CoInitialize(nil);
finalization
CoUninitialize;
Example is using windows MSXML2 interface which you can get here:
MSXML2_TLB.pas
Use XMLHTTPRequest to get http page (instead of TIdHttp) and pass response to my ParseHTM4String function and XPath search string.
Usage:
GetHTMLInfo('http://de.wikipedia.org/wiki/Physik',
Edit1.Text, sResult, sError);
//sResult is result ....
Line
XMLDomDoc.setProperty('SelectionLanguage', 'XPath');
@sinisav
Excellent stuff! Thank you very much.
Unfortunately, it does not work with a different web page. Your code gives the error "The character '>' was expected". I checked the web page with a HTML validator and it validates ok. Do you have an idea what is going wrong?
I attached my program so you can ran it straight away.
Regards,
Dirk.
XPath.zip
Excellent stuff! Thank you very much.
Unfortunately, it does not work with a different web page. Your code gives the error "The character '>' was expected". I checked the web page with a HTML validator and it validates ok. Do you have an idea what is going wrong?
I attached my program so you can ran it straight away.
Regards,
Dirk.
XPath.zip
until now I have no success too.
I remove dtd checking by remove first line of html (this will speed up parsing too):
Now I get:
Maybe is something wrong on this site (set in XPath.zip source)....
I remove dtd checking by remove first line of html (this will speed up parsing too):
sHTM := XMLHTTPRequest.responseText;
Delete(sHTM, 1, Pos('<html', sHTM)-1);
Result := ParseHTM4String(sHTM, sXPath, sResponse, sError);
Now I get:
End tag 'head' does not match the start tag 'link'.
Maybe is something wrong on this site (set in XPath.zip source)....
I wrote my program now in C# and it works like a charm. So I suppose there is nothing wrong on the site; there is rather a bug in the XPath parser.
This is unfortunate for me since I'd prefer to have this program written in Delphi.
But anyway, this site was not part of my question and your program solved it. Therefore, thank you vey much for your effort.
This is unfortunate for me since I'd prefer to have this program written in Delphi.
But anyway, this site was not part of my question and your program solved it. Therefore, thank you vey much for your effort.
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I tried so many things which didn't work. That's why I need a working sample not just a link to a weg page that has something about XML and XPath on it.
For example that fails:
var
lXmlDoc: IXMLDOMDocument;
lPage: String; // Web site content
begin
lXmlDoc := CoDOMDocument.Create;
lXmlDoc.load(lPage);