xml-canonicalizer.md

XMLCanonicalizer

A VFP class to canonicalize an XML document, according to W3C specifications (although not fully).

The class stands on the XMLSerializer class, which is required to prepare a VFP version of the document that will be canonicalized.

The main purpose of canonical XML it to provide a basis for the creation and validation of signed documents.

Part of VFP XML library set.

Usage

*!* install the library
DO LOCFILE("xml-canonicalizer.prg")
*!* instantiate an object
m.XMLCanon = CREATEOBJECT("XMLCanonicalizer")
*!* call methods...

Components

• xml-canonicalizer.prg

Dependencies

• XMLSerializer

Methods

Canonicalize()

m.XML = m.XMLCanon.Canonicalize (m.Source[, m.XPath[, m.Namespaces]])

Reads an XML document from a string, a URL, a file, or a DOM node, and returns its canonicalized form, as a text. The canonicalization may start at the point determined by the m.XPath expression (the m.Namespaces parameter may be used to reference namespaces in the expression, and may take the form of a string or a collection of namespaces, keyed by their prefixes).

Example (from W3C test cases):

<!DOCTYPE doc [<!ATTLIST e9 attr CDATA "default">]>
<doc>
   <e1   />
   <e2   ></e2>
   <e3   name = "elem3"   id="elem3"   />
   <e4   name="elem4"   id="elem4"   ></e4>
   <e5 a:attr="out" b:attr="sorted" attr2="all" attr="I'm"
      xmlns:b="http://www.ietf.org"
      xmlns:a="http://www.w3.org"
      xmlns="http://example.org"/>
   <e6 xmlns="" xmlns:a="http://www.w3.org">
      <e7 xmlns="http://www.ietf.org">
         <e8 xmlns="" xmlns:a="http://www.w3.org">
            <e9 xmlns="" xmlns:a="http://www.ietf.org"/>
         </e8>
      </e7>
   </e6>
</doc> 

results in a canonicalized XML document (EXC-C14N)

<doc>
   <e1></e1>
   <e2></e2>
   <e3 id="elem3" name="elem3"></e3>
   <e4 id="elem4" name="elem4"></e4>
   <e5 xmlns="http://example.org" xmlns:a="http://www.w3.org" xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e5>
   <e6>
      <e7 xmlns="http://www.ietf.org">
         <e8 xmlns="">
            <e9 attr="default"></e9>
         </e8>
      </e7>
   </e6>
</doc>

or, inclusively, in (C14N)

<doc>
   <e1></e1>
   <e2></e2>
   <e3 id="elem3" name="elem3"></e3>
   <e4 id="elem4" name="elem4"></e4>
   <e5 xmlns="http://example.org" xmlns:a="http://www.w3.org" xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e5>
   <e6 xmlns:a="http://www.w3.org">
      <e7 xmlns="http://www.ietf.org">
         <e8 xmlns="">
            <e9 xmlns:a="http://www.ietf.org" attr="default"></e9>
         </e8>
      </e7>
   </e6>
</doc>

SetMethod()

m.XMLCanon.SetMethod(m.MethodURI)

Sets the canonicalization method, according to its algorithm URI.

SetInclusiveNamespaces()

m.XMLCanon.SetInclusiveNamespaces(m.PrefixList)

Sets the list of namespaces that will be canonicalized inclusively during an exclusive canonicalization.

SetOption()

m.XMLCanon.SetOption(m.Option)

Sets (by activating) canonicalization options.

Options

• "Default" (reset all options)
• "Exclusive" (defaults to true)
• "Inclusive" (defaults do false)
• "Comments" (defaults to false)
• "No-Comments" (defaults to true)
• "Trim" (defaults to false)