在XPATH表达式中像变量一样使用元素的值？

Question

So I'm just trying to figure out whether its possible to select the value of element inside xpath like a variable? Is this possible? If not what are some user friendly method of achieving this?

XML

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="grades.xsl"?>
<school>
 <subject Id="3311">
 <className>English</className>
 <studentList>
 <student id="1001">Lisa Simpson</student>
 <student id="1002">Barney Rubble</student>
 <student id="1003">Donald Duck</student>
 </studentList>
 <classwork>
 <assignment name="Final Exam">
 <mark studId="1001">38</mark>
 <mark studId="1002">21</mark>
 <mark studId="1003">20.5</mark>
 </assignment>
 </classwork>
 </subject>
</school>

XSL

    <td><xsl:value-of select="@sid"/></td>
    <td><xsl:value-of select="//assignment/mark[@studId='@sid']"/></td>

Answer 1

I suspect you real question is how to get the student's marks from the context of student .

This can be done using:

<xsl:value-of select="//assignment/mark[@studId=current()/@id]"/>

---

A better answer is to define a key at the top level of your stylesheet as:

<xsl:key name="marks" match="mark" use="@studId" />

then use the expression key('mark', @id) to get the related marks.

For example, the following stylesheet:

XSLT 1.0

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="utf-8" indent="yes"/>

<xsl:key name="marks" match="mark" use="@studId" />

<xsl:template match="/school">
    <table border="1">
        <xsl:for-each select="subject/studentList/student">
            <tr>
                <td>
                    <xsl:value-of select="."/>
                </td>
                <td>
                    <xsl:value-of select="key('marks', @id)"/>
                </td>
            </tr>
        </xsl:for-each>
    </table>
</xsl:template>

</xsl:stylesheet>

applied to your input example, will show:

---

Not that the examples assume each student has at most one mark.