Re: [xml] XPath Woes

["William M. Brack" <wbrack mmm com hk>]

mt2 wrote:
> Hello all,
>
> I'm working on a very simple project to parse ROAP messages, part of
> the OMA DRM, for the moment. Libxml2 fits the bill for this project,
> so thank you! I am using XPath to query the document:
> /roap:riHello/extensions/extension[ xsi:type="roap:CertificateCaching"].
> I am trying to get a node returned: <extension
> xsi:type="roap:CertificateCaching" />. Unfortunately, I get no results
> from libxml, but I have tested this against MSXML and an online XPath
> environment. If anyone has any ideas, I'd appreciate it!

I tried your xml file and XPath query using the example program
'xpath1' included in libxml2 distribution, and got the following
results (note that the following command should all be on a single
line):

[bill bbxp work]$ ./xpath1 bug.xml
'/roap:riHello/extensions/extension[ xsi:type="roap:CertificateCaching"]'
"xsi=http://www.w3.org/2001/XMLSchema-instance
roap=urn:oma:bac:dldrm:roap-1.0"
Result (1 nodes):
= element node "extension"
[bill bbxp work]$

Perhaps you could analyze what is the difference between your code,
and the way in which this example program behaves (which appears to be
correct)?

> The code:
>  xpathCtx = xmlXPathNewContext(doc);
> xmlXPathRegisterNs(xpathCtx, (xmlChar *)"roap", (xmlChar
> *)"urn:oma:bac:dldrm:roap-1.0");
> xmlXPathRegisterNs(xpathCtx, (xmlChar *)"xsi", (xmlChar
> *)"http://www.w3.org/2001/XMLSchema-instance";);
>
> xpathObj =
> xmlXPathEvalExpression("/roap:riHello/extensions/extension[ xsi:type=\"roap:CertificateCaching\"]",
> xpathCtx);
>
> if (xpathObj->nodesetval->nodeNr > 0)
>
> XML:
> <?xml version="1.0" encoding="utf-8"?>
> <roap:riHello xmlns:roap="urn:oma:bac:dldrm:roap-1.0"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; status="Success"
> sessionId="433211">
>   <selectedVersion>1.0</selectedVersion>
>   <riID>
>     <keyIdentifier xsi:type="roap:X509SPKIHash">
>       <hash>aXENc+Um/9/NvmYKiHDLaErK0gk</hash>
>     </keyIdentifier>
>   </riID>
>   <riNonce>dsaiuiure9sdwerfqwer</riNonce>
>   <trustedAuthorities>
>     <keyIdentifier xsi:type="roap:X509SPKIHash">
>       <hash>aXENc+Um/9/NvmYKiHDLaErK0gk</hash>
>     </keyIdentifier>
>     <keyIdentifier xsi:type="roap:X509SPKIHash">
>       <hash>aXENc+Um/9/NvmYKiHDLaErK0gk</hash>
>     </keyIdentifier>
>   </trustedAuthorities>
>   <extensions>
>     <extension xsi:type="roap:CertificateCaching" />
>   </extensions>
> </roap:riHello>

Bill