XPATH: Selecting multiple records with Wildcard Namespaces

问题

I am fairly new to XPATH and need to return a value from multiple XML objects when a certain node is equal to one of two values. The solution also needs to be namespace agnostic using local-name(). Given the following XML, I am looking to return all of the values of "B" where "A" is equal to either "4" or "5".

<?xml version="1.0"?>
    <element>
        <A>3</A>
        <B>Value 1</B>
    </element>
    <element>
        <A>4</A>
        <B>Value 2</B>
    </element>
    <element>
        <A>5</A>
        <B>Value 3</B>
    </element>

I have tried many iterations of the following expression but cannot seem to get the syntax correct when I try to add the second value for "A". I just can't seem to figure out the correct syntax for an "or" expression. I have also considered the use of a union and couldn't get that syntax correct either.

This works for when "A" equals a single value of "4" but how to I add the test for a value of "5" so that the result returns two values for "B" ("Value 2" and "Value 3")?

//*[local-name()='element'][*[local-name()='A']='4']/*[local-name()='B']/text()

Thank you. Any help would be very much appreciated!

回答1:

Try this:

//*[local-name() = 'element']/*[local-name() = 'A' and (. = 4 or . = 5)]
    /../*[local-name() = 'B']

This expression selects Value 2 and Value 3.

回答2:

The proper way of treating namespaces is to register them with your XPath API and to ...use them in the XPath expression:

Use:

//x:element[x:A = 4 or x:A = 5]/x:B

XSLT - based verification:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:x="some:default NS">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="/">
     <xsl:copy-of select="//x:element[x:A = 4 or x:A = 5]/x:B"/>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the following XML document (the provided fragment, wrapped by a single top element that has a default namespace definition):

<t xmlns="some:default NS">
    <element>
        <A>3</A>
        <B>Value 1</B>
    </element>
    <element>
        <A>4</A>
        <B>Value 2</B>
    </element>
    <element>
        <A>5</A>
        <B>Value 3</B>
    </element>
</t>

the XPath expression is evaluated and the result (selected nodes) of this evaluation is copied to the output:

<B xmlns="some:default NS">Value 2</B>
<B xmlns="some:default NS">Value 3</B>

回答3:

You can nest predicates.

//*[
  local-name() = 'element' and *[local-name() = 'A' and (. = 4 or . = 5)]
]/*[
  local-name() = 'B'
]/text()

But in reality you should be using namespace-aware XPath:

//ns1:element[ns2:A[. = 4 or . = 3]]/ns2:B/text()

来源：https://stackoverflow.com/questions/13463871/xpath-selecting-multiple-records-with-wildcard-namespaces

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xml

xpath

selection

record