How to query HTML with x XPath expression in C++? - c++

Question

I have a webbrowser and I use DocumentComplete to read the current document from the WebBrowser (as IHTMLDocument2).
What's the easiest way to run xpath queries in that html doc? I am looking for something easy to use and lightweight.
I am using Visual Studio C++ 2010.

Answer 1

What's the easiest way to run xpath
queries in that html doc? I am looking
for something easy to use and
lightweight.
I am using Visual Studio C++ 2010.
Generally, XPath expressions cannot be evaluated against HTML documents.
However, if the HTML document is also an XHTML document (which is by definition a well-formed XML document), then XPath expressions can be evaluated against it.
In particular using MS Visual C++, one can use code like this:
#include <stdio.h>
#import <msxml3.dll>
using namespace MSXML2;
void dump_com_error(_com_error &e);
int main(int argc, char* argv[])
{
CoInitialize(NULL);
try{
IXMLDOMDocument2Ptr pXMLDoc = NULL;
HRESULT hr = pXMLDoc.CreateInstance(__uuidof(DOMDocument30));
// Set parser property settings
pXMLDoc->async = VARIANT_FALSE;
// Load the sample XML file
hr = pXMLDoc->load("hello.xsl");
// If document does not load report the parse error
if(hr!=VARIANT_TRUE)
{
IXMLDOMParseErrorPtr pError;
pError = pXMLDoc->parseError;
_bstr_t parseError =_bstr_t("At line ")+ _bstr_t(pError->Getline())
+ _bstr_t("\n")+ _bstr_t(pError->Getreason());
MessageBox(NULL,parseError, "Parse Error",MB_OK);
return 0;
}
// Otherwise, build node list using SelectNodes
// and returns its length as console output
else
pXMLDoc->setProperty("SelectionLanguage", "XPath");
// Set the selection namespace URI if the nodes
// you wish to select later use a namespace prefix
pXMLDoc->setProperty("SelectionNamespaces",
"xmlns:xsl='http://www.w3.org/1999/XSL/Transform'");
IXMLDOMElementPtr pXMLDocElement = NULL;
pXMLDocElement = pXMLDoc->documentElement;
IXMLDOMNodeListPtr pXMLDomNodeList = NULL;
pXMLDomNodeList = pXMLDocElement->selectNodes("//xsl:template");
int count = 0;
count = pXMLDomNodeList->length;
printf("The number of <xsl:template> nodes is %i.\n", count);
}
catch(_com_error &e)
{
dump_com_error(e);
}
return 0;
}
void dump_com_error(_com_error &e)
{
printf("Error\n");
printf("\a\tCode = %08lx\n", e.Error());
printf("\a\tCode meaning = %s", e.ErrorMessage());
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
printf("\a\tSource = %s\n", (LPCSTR) bstrSource);
printf("\a\tDescription = %s\n", (LPCSTR) bstrDescription);
}
Read more about this code example here.