Like Bob said, the prefixes used in the document and in the XPath expression
are irrelevent - what matters is the URI that the prefix maps to in the
document and the URI that the prefix is mapped to in the XPath expression.
The NamespaceContext in Jaxen defines what the namespace prefixes map to in
the XPath expression.
So using "x" to map to "someURI" in NamespaceContext should be fine, even if
the namespace prefix is different in the document.
James
----- Original Message -----
From: "Frank Sauer" <[EMAIL PROTECTED]>
To: "'James Strachan'" <[EMAIL PROTECTED]>; "Erwin Bolwidt"
<[EMAIL PROTECTED]>
Cc: "jaxen-interest" <[EMAIL PROTECTED]>
Sent: Friday, September 21, 2001 7:32 PM
Subject: RE: [Jaxen] RE: some followup info
> But that's still not going to work because the xml elements
> don't have the prefix. So even if I add
> a mapping from x to "http://.......";, the XML contains this
> stupid xmlns="http://....."; as a #FIXED attribute declared in
> an offical J2EE DTD..... So the elements don't use a prefix.
> I printed the prefix and URI for the Namespace object I get from
> JDOM in this attempt to solve the problem:
>
> private String eval(Element context, String expr) {
> try {
> XPath xpath = new XPath( expr );
> Namespace ns = context.getNamespace();
> if ((ns != null) && (ns != Namespace.NO_NAMESPACE)) {
> SimpleNamespaceContext nsc = new SimpleNamespaceContext();
> System.err.println("Setting NamespaceContext for " +
ns.getPrefix()
> + " to " + ns.getURI());
> nsc.addNamespace(ns.getPrefix(), ns.getURI());
> xpath.setNamespaceContext(nsc);
> }
> List results = xpath.selectNodes( context );
>
> But you're right, now the functions don't resolve...:
>
> Setting NamespaceContext for to
> http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd
> org.jaxen.UnresolvableException: Function :concat
> at
> org.jaxen.SimpleFunctionContext.getFunction(SimpleFunctionContext.java:43)
> at org.jaxen.ContextSupport.getFunction(ContextSupport.java:114)
> at org.jaxen.Context.getFunction(Context.java:67)
> at
>
org.jaxen.expr.DefaultFunctionCallExpr.evaluate(DefaultFunctionCallExpr.java
> :122)
> at org.jaxen.expr.DefaultXPath.asList(DefaultXPath.java:46)
> at org.jaxen.JaXPath.jaSelectNodes(JaXPath.java:35)
> at org.jaxen.BaseXPath.selectNodes(BaseXPath.java:22)
> at
>
com.trcinc.xmltalk.xml.dtd.DTDCatalog$CatalogEntry.eval(DTDCatalog.java:150)
>
>
> By the way, I thought I saw in earlier versions of Jaxen an
> addNamespaceContext so
> Frank Sauer
> The Technical Resource Connection, Inc.
> a wholly owned subsidiary of Perot Systems
> Tampa, FL
> http://www.trcinc.com
> -----------------------------------------------
> Java: The best argument for Smalltalk since C++
>
>
> -----Original Message-----
> From: James Strachan [mailto:[EMAIL PROTECTED]]
> Sent: Friday, September 21, 2001 11:16 AM
> To: Erwin Bolwidt
> Cc: Frank Sauer; 'bob mcwhirter'; jaxen-interest
> Subject: Re: [Jaxen] RE: some followup info
>
>
> From: "Erwin Bolwidt" <[EMAIL PROTECTED]>
> > On Fri, 21 Sep 2001, James Strachan wrote:
> >
> > > You can bind the empty prefix to a namespace URI. Its often called the
> > > 'default namespace'.
> > >
> > > e.g.
> > >
> > > <foo xmlns="someURI">
> > > <bar/>
> > > </foo>
> > >
> > > In the above document the XPath expression /foo/bar will not work
unless
> you
> > > explicitly setup a NamespaceContext to set the default namespace URI
to
> be
> > > "someURI". If you map empty prefix, "", to "someURI" in your
> > > NamespaceContext then /foo/bar will work.
> >
> > That would have been convenient if it were possible, but there are two
> > problems:
> >
> > * xpath explicitly disallows it, in section 2.3:
> > "A QName in the node test is expanded into an expanded-name using the
> > namespace declarations from the expression context. This is the same way
> > expansion is done for element type names in start and end-tags except
> > that the default namespace declared with xmlns is not used: if the
> > QName does not have a prefix, then the namespace URI is null (this is
the
> > same way attribute names are expanded). It is an error if the QName has
a
> > prefix for which there is no namespace declaration in the expression
> > context."
> >
> > * a practical one: functions and variables are also qualified names; if
> > you were to rebind the empty prefix to some namespace, then you wouldn't
> > be able to call any of the built-in xpath functions, since they have no
> > namespace URI. Jaxen simply won't be able to find the functions or
> > variables.
>
> Ah OK. Thats a huge shame but I guess to work with non-namespaced
functions
> and variables it has to be like that.
>
> Thanks for clearing that up - I stand corrected. The only way to properly
> evaluate that XPath expression is then this ugly huge thing...
>
> /*[local-name()='foo' and namespace-uri()='someURI']//*[local-name()='bar'
> and namespace-uri()='someURI']/
>
> Though I suppose you could map your own new prefix to the URI instead. So
> rather than mapping "" to "someURI" you could map "x" to "someURI" and
then
> do
>
> /x:foo/x:bar
>
> which should work.
>
> James
>
>
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