XSLT xsl:choose

In XSLT (Extensible Stylesheet Language Transformations), the xsl:choose element is used to perform conditional processing. It is part of the XSLT control structures and allows you to choose one of several alternative blocks of code to execute based on specific conditions.

The xsl:choose element is often used in conjunction with xsl:when and xsl:otherwise elements to define the different conditional branches. Here’s the basic syntax of the xsl:choose element:

<xsl:choose>
  <xsl:when test="condition-1">
    <!-- Code block to execute when condition-1 is true -->
  </xsl:when>
  <xsl:when test="condition-2">
    <!-- Code block to execute when condition-2 is true -->
  </xsl:when>
  <!-- More <xsl:when> blocks can be added as needed -->
  <xsl:otherwise>
    <!-- Code block to execute if none of the conditions are true -->
  </xsl:otherwise>
</xsl:choose>

In this structure:

• The xsl:when elements are used to define individual conditions. Each xsl:when element has a test attribute that specifies the XPath expression for evaluating the condition.
• The xsl:otherwise element is optional and provides a default code block to execute if none of the conditions in the xsl:when elements are true.

The xsl:choose element evaluates the conditions in order and executes the code block corresponding to the first true condition. If none of the conditions are true and there is an xsl:otherwise element, its code block will be executed.

Here’s an example of using xsl:choose to handle different salary ranges:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/">
    <xsl:choose>
      <xsl:when test="salary &lt; 30000">
        <xsl:text>Low salary.</xsl:text>
      </xsl:when>
      <xsl:when test="salary &lt; 50000">
        <xsl:text>Medium salary.</xsl:text>
      </xsl:when>
      <xsl:otherwise>
        <xsl:text>High salary.</xsl:text>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>
</xsl:stylesheet>

In this example, if the value of the “salary” element in the XML input is less than 30,000, it will output “Low salary.” If it is between 30,000 and 50,000, it will output “Medium salary.” Otherwise, it will output “High salary.”

xsl:choose is a powerful construct in XSLT that allows you to handle complex conditional logic and tailor the transformation output based on specific conditions in the input data.