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From Tim Stephenson <tstep...@tibco.com>
Subject How to specify namespace context for jstl x tags?
Date Wed, 15 Apr 2009 23:25:57 GMT

> Hi,
>
> I have a feeling this must be a common problem but I'm afraid I can't 
> find the answer...
>
> I am trying to use the JSTL x tags in v1.1.2 of the 'standard' tag 
> library. Something like this:
>    <c:import   url="WorkItem.xml"    var="url" />
>    <x:parse       xml="${url}"     var="doc"   />
>    <x:out     select="$doc/ap:ActionResult"  />
>
> The problem is the namespace in my XPath query and it results in the 
> error:       
> com.sun.org.apache.xpath.internal.domapi.XPathStylesheetDOM3Exception: 
> Prefix must resolve to a namespace: ap
>
> Fair enough. But how can I tell the x:out tag about the namespace?
>
> In Java I would write a NamespaceContext implementation and supply 
> that to the XPath engine. Something like this:
>                NamespaceContext ctx = new NamespaceContext() {
>                public String getNamespaceURI(String prefix) {
>                    String uri;
>                    if (prefix.equals("ap"))
>                        uri = "http://example.com/ap";
>                    else
>                        uri = null;
>                    return uri;
>                }
>
>                // Dummy implementation - not used!
>                public Iterator getPrefixes(String val) {
>                    return null;
>                }
>
>                // Dummy implemenation - not used!
>                public String getPrefix(String uri) {
>                    return null;
>                }
>            };
>
>            // Now the XPath expression
>            String xpathStr = "/ap:ActionResult";
>            XPathFactory xpathFact = XPathFactory.newInstance();
>            XPath xpath = xpathFact.newXPath();
>            xpath.setNamespaceContext(ctx);
>            String result = xpath.evaluate(xpathStr, doc);
>
> In JSTL it seems there is no equivalent? Is there any 'under the 
> radar' way to supply the namespace context to the tag?
>
> Seems a real shame to have to write a new taglib just to support this...
> thanks for your suggestions,
> Tim
>

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