Xpath and parameters

Question

I am relatively new to XSL and I think this is a basic question. So I better get my apologies in early!

Basically, I would like to use a value-of function. This will be in a template and I would like to pass part of the xpath as a parameter.

<xsl:variable name="TEST_VAR">"h:elementA/elementB"</xsl:variable>

... and then use the variable  (or passed in param) as all (or part) of the xpath:

<xsl:element name="transformedElement"><xsl:value-of select=$TEST_VAR/></xsl:element>

I would really like to have the xpath to be a mixture of string literals and the vlue of TEST_VAR.

Thanks in advance

Answer 1

What you want to do can't be done. You cannot interpret plain strings as XPath expressions within an XSL transform.

But you shouldn't have to, anyway. By the looks of it you can replace your example with the following to get what you want:

<xsl:variable name="TEST_VAR" select="h:elementA/elementB"/>
<xsl:element name="transformedElement">
  <xsl:value-of select="$TEST_VAR"/>
</xsl:element>

But I suspect you've dumbed down your example to the point that it's too simple to see what you actually want.

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Answer 2

Pass the desired XPath expression as a global <xsl:param>. If the name of this global parameter is vQuery then you can use code like this:

<xsl:element name="transformedElement"> 
  <xsl:value-of select=
     "*[name() = substring-before($vQuery, '/')]
                 /*[name() = substring-after($vQuery, '/')]"/> 
</xsl:element>

Such technique generally requires that you have a lot of knowledge about the XPath expression that will be passed. In this case it relies on the fact that this is a relative XPath expression with exactly two location steps and no predicates in them.