Re: [xsl] Why doesn't this simple XSLT (Identity transform) work?

[<ohaya@xxxxxxx>]

Hi Ken,

Thanks, not just for the solution, but for the VERY detailed explanation.  I know that I'll have to re-re-read your post, probably several more times, but if I'm understanding, basically the problem was that the match I was using was not matching anything, so that xsl:template was not "catching", and the reason for not matching was because of the namespace.

Is that right?

Thanks again,
Jim

 


---- "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx> wrote: 
> At 2009-12-01 19:43 -0500, ohaya@xxxxxxx wrote:
> >It's been awhile since I've worked with XSLT, but I'm having to 
> >implement one that removes an element (<Signature>) from the 
> >incoming (SOAP) message.
> 
> Actually, you want to remove the element:
> 
>   {http://www.w3.org/2000/09/xmldsig#}Signature
> 
> ... regardless of the prefix used in the syntax of the input XML.
> 
> >I know that this should be simple, and I know that I have written 
> >similar XSLT before, but for some reason, I can get this to work.
> 
> You are forgetting that XSLT matches on the expanded name of a node 
> and not the specified name of the node.  Prefixes are irrelevant 
> (other than playing the role of associating the namespace URI string 
> for the expanded name).
> 
> >Here's an example SOAP message:
> >...
> >And, here's the XSLT that I'm using:
> >...
> 
> Thank you for providing the plug-and-play.
> 
> >What the XSLT seems to be doing is just doing the Identity 
> >transform, and copying everything from the input message to the 
> >output, i.e., the "<xsl:template match="//Signature">" is not 
> >getting processed at all.
> 
> Right.  And, BTW, the "//" isn't needed, but that isn't what is wrong.
> 
> >I've tried different things for that template match, including just 
> >"Signature", a "fully-qualified" match term, etc.
> 
> You didn't try a qualified name match.  A qualified name has as its 
> lexical space the specified name for the element and as its value 
> space the expanded name for the element.  Two qualified names are 
> compared by their expanded names.  A qualified name is exposed and 
> written using the specified name and the in-scope namespaces for the 
> prefix used or not by the specified name.
> 
> >I have the impression that the XSLT processing should always use the 
> >more specific match (i.e., the one above, and not the Identity 
> >transform), but it doesn't seem to be working :(...
> 
> That isn't true in general but happens to be true in this case, you 
> just haven't named the element properly.
> 
> Some of the detail relevant to your situation is that every match 
> pattern that is more complex than a simple name has the same inferred 
> priority of 0.5, without any kind of "increasing level of complexity 
> based on length", just 0.5 full stop.  A simple name has the inferred 
> priority of 0.  A wild card has the inferred priority of 
> -0.5.  (There are a couple others not in play here)  Since all of 
> your template rules that match the Signature element have different 
> priorities, the one that is highest (the simple name) trumps the 
> lower one (the element wild card).
> 
> >I'm sure that I am missing something really obvious here,
> 
> The qualified element name in your XSLT has to match the qualified 
> element name in the XML (in the value space, not in the lexical 
> space, thus the expanded names must be equal).
> 
> The specified element name in your XSLT has no relation to the 
> specified element name in the XML (the lexical space).
> 
> I hope the solution below illustrates this for you.
> 
> . . . . . . . . . . Ken
> 
> t:\ftemp>type ohaya.xml
> <SOAP:Envelope xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion" 
> xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol" 
> xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/"; 
> xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"; 
> xmlns:env="http://schemas.xmlsoap.org/soap/envelope/";>
>      <SOAP:Header>
>          <wsse:Security SOAP:mustUnderstand="1">
>              <saml:Assertion MajorVersion="1" MinorVersion="1" 
> AssertionID="ID46a342be-9d3a-437a-8a26-85fcd72a723d" 
> Issuer="http://foo.com"; IssueInstant="2009-12-01T21:55:13Z">
>                  <saml:Conditions NotBefore="2009-12-01T21:54:58Z" 
> NotOnOrAfter="2009-12-01T22:10:28Z"/>
>                  <saml:AuthenticationStatement 
> AuthenticationMethod="urn:oasis:names:tc:SAML:1.0:am:unspecified" 
> AuthenticationInstant="2009-12-01T21:55:13Z">
>                  .....
>                  </saml:AuthenticationStatement>
>               <Signature xmlns="http://www.w3.org/2000/09/xmldsig#";>
>                    ...
>               </Signature></saml:Assertion></wsse:Security>
> </SOAP:Header>
> <env:Body>
>          <m:hello xmlns:m="http://services";>
>              <m:x>123</m:x></m:hello>
> </env:Body>
> </SOAP:Envelope>
> 
> t:\ftemp>call xslt ohaya.xml ohaya.xsl
> <?xml version="1.0" encoding="utf-8"?><SOAP:Envelope 
> xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/"; 
> xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion" 
> xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol" 
> xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"; 
> xmlns:env="http://schemas.xmlsoap.org/soap/envelope/";>
>      <SOAP:Header>
>          <wsse:Security SOAP:mustUnderstand="1">
>              <saml:Assertion MajorVersion="1" MinorVersion="1" 
> AssertionID="ID46a342be-9d3a-437a-8a26-85fcd72a723d" 
> Issuer="http://foo.com"; IssueInstant="2009-12-01T21:55:13Z">
>                  <saml:Conditions NotBefore="2009-12-01T21:54:58Z" 
> NotOnOrAfter="2009-12-01T22:10:28Z"/>
>                  <saml:AuthenticationStatement 
> AuthenticationMethod="urn:oasis:names:tc:SAML:1.0:am:unspecified" 
> AuthenticationInstant="2009-12-01T21:55:13Z">
>                  .....
>                  </saml:AuthenticationStatement>
>               </saml:Assertion></wsse:Security>
> </SOAP:Header>
> <env:Body>
>          <m:hello xmlns:m="http://services";>
>              <m:x>123</m:x></m:hello>
> </env:Body>
> </SOAP:Envelope>
> t:\ftemp>type ohaya.xsl
> <?xml version="1.0" encoding="utf-8"?>
> <xsl:stylesheet version="1.0" 
> xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; 
> xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"; 
> xmlns:dp="http://www.datapower.com/extensions";
>      xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/";
>      xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion"
>      xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol"
>      xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd";
>      xmlns:sig="http://www.w3.org/2000/09/xmldsig#";
>  >
>      <xsl:output method="xml"/>
> 
>      <xsl:template match="node()|@*">
>          <xsl:copy>
>              <xsl:apply-templates select="node()|@*"/>
>          </xsl:copy>
>      </xsl:template>
> 
>      <xsl:template match="sig:Signature">
>      </xsl:template>
> 
> </xsl:stylesheet>
> 
> t:\ftemp>rem Done!
> 
> 
> 
> --
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