<xsl:key> tag element specifies a named name-value pair assigned to a specific element in an XML document. This key is used with the key() function in XPath expressions to access the assigned elements in an XML document.
Declaration
Following is the syntax declaration of <xsl:key> element.
<xsl:key name = QName match = Pattern use = Expression > </xsl:key>
Attributes
| S.No | Name & Description |
|---|---|
| 1 | NameName of the key to be used. |
| 2 | MatchPatterns used to identify a node that holds this key. |
| 3 | UseXPath expression to identify the value of the nodes of xml document. |
Elements
| Number of Occurrences | Unlimited |
| Parent elements | xsl:stylesheet |
| Child elements | None |
Demo Example
This example creates a table of <student> element with its attribute rollno and its child <firstname>, <lastname>, <nickname>, and <marks> by iterating over each student. It checks key as firstname to be one of the student’s name and then prints the student details.
students.xml
<?xml version = "1.0"?>
<?xml-stylesheet type = "text/xsl" href = "students.xsl"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vaneet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
students.xsl
<xsl:stylesheet version = "1.0"
xmlns:xsl = "http://www.w3.org/1999/XSL/Transform">
<xsl:key name = "firstname-search" match = "student" use = "firstname"/>
<xsl:template match = "/">
<html>
<body>
<h2>Students</h2>
<table border = "1">
<tr bgcolor = "#9acd32">
<th>Roll No</th>
<th>First Name</th>
<th>Last Name</th>
<th>Nick Name</th>
<th>Marks</th>
</tr>
<xsl:for-each select = "key('firstname-search', 'Dinkar')">
<tr>
<td><xsl:value-of select = "@rollno"/></td>
<td><xsl:value-of select = "firstname"/></td>
<td><xsl:value-of select = "lastname"/></td>
<td><xsl:value-of select = "nickname"/></td>
<td><xsl:value-of select = "marks"/></td>
</tr>
</xsl:for-each>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
Output
