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Re: XSL/XPath to generate a list of ancestors?

Subject: Re: XSL/XPath to generate a list of ancestors?
From: Nathan Potter <ndp@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 12 May 2008 09:54:24 -0700
Re:  XSL/XPath to generate a list of ancestors?
On May 12, 2008, at 9:13 AM, Michael Kay wrote:


<xsl:template match="*" name="fullNameWorker" mode="fullName"> <xsl:if test=".!=/"> <xsl:apply-templates select=".." mode="fullName"/> <xsl:if test="..!=/">.</xsl:if> <xsl:value-of select="@name"/> </xsl:if> </xsl:template>

Never use != to compare node identity. It can be very expensive and it gives
the wrong answer. For example if your document is


<doc><subdoc>
    ...
  </subdoc></doc>

then doc and subdoc both compare equal to "/", and if the document is 100Mb
in size then you will be comparing some very long strings to prove it.


In 2.0, use "is". In 1.0, use generate-id(A)=generate-id(B).

I tried this:


     <xsl:template match="*" name="fullNameWorker" mode="fullName">
        <xsl:if test="generate-id(.)!=generate-id(/)">
            <xsl:apply-templates select=".." mode="fullName"/>
            <xsl:if test="generate-id(..)!=generate-id(/)">.</xsl:if>
            <xsl:value-of select="@name"/>
        </xsl:if>
     </xsl:template>

And it just nuked the stack when I tried to apply the transform:

Exception in thread "main" java.lang.StackOverflowError
at org.jdom.Verifier.checkXMLName(Verifier.java:604)
at org.jdom.Verifier.checkAttributeName(Verifier.java:116)
at org.jdom.Attribute.setName(Attribute.java:360)
at org.jdom.Attribute.<init>(Attribute.java:228)
at org.jdom.Attribute.<init>(Attribute.java:276)
at org.jdom.DefaultJDOMFactory.attribute(DefaultJDOMFactory.java:93)
at org.jdom.input.SAXHandler.startElement(SAXHandler.java:544)
at org.xml.sax.helpers.XMLFilterImpl.startElement(XMLFilterImpl.java: 527)
at org.jdom.transform.JDOMResult$DocumentBuilder.startElement (JDOMResult.java:519)
at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.closeStartTag (ToXMLSAXHandler.java:205)
at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.characters (ToXMLSAXHandler.java:524)
at GregorSamsa.constraintTagWorker()
at GregorSamsa.applyTemplates4()
at GregorSamsa.applyTemplates4()


(Which leads me to ask: Why is there a Kafka character lurking in my XSLT implementation?)

Some how the recursion gets out of control.



Some more context for the XSL:


The goal was that when processing an element I need to generate it's linage in a "." separated string. So I need to insert a tag containing this lineage string into the element that is being processed/




    <xsl:template name="fullName">
        <fullName>
            <xsl:call-template name="fullNameWorker" />
        </fullName >
    </xsl:template>

    <xsl:template match="*" name="fullNameWorker" mode="fullName">
        <xsl:if test=".!=/">
            <xsl:apply-templates select=".." mode="fullName"/>
            <xsl:if test="..!=/">.</xsl:if>
            <xsl:value-of select="@name"/>
        </xsl:if>
    </xsl:template>

    <xsl:template match="*">
        <myNewNode>
		<xsl:call-template name="fullName">
	</myNewNode>
    </xsl:template>







Michael Kay http://www.saxonica.com/


============================================================ Nathan Potter Oregon State University, COAS ndp at coas.oregonstate.edu 104 Ocean. Admin. Bldg. 541 737 2293 voice Corvallis, OR 97331-5503 541 737 2064 fax

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