XSLT Transform - Coding

What is XSLT Transform?

An XSLT transform is the process of applying an XSLT stylesheet to an XML document to produce a new document or presentation of the data. The XSLT stylesheet contains a set of rules and instructions that define how the transformation should occur.

Syntax:

<!-- Example XSLT stylesheet -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  
  <!-- Template for matching the root element of the XML document -->
  <xsl:template match="">
    <html>
      <body>
        <h2>Transformed Output</h2>
      </body>
    </html>
  </xsl:template>
  
  <!-- Template for matching specific elements in the XML document -->
  <xsl:template match="book">
    <p><xsl:value-of select="title"/></p>
  </xsl:template>

</xsl:stylesheet>

The <xsl:stylesheet> element is the root element that declares the XSLT stylesheet.
The version attribute indicates the XSLT version being used.
The xmlns:xsl attribute defines the XML namespace for XSLT.
<xsl:template> elements define templates for matching specific elements in the XML document.
The match attribute specifies the pattern to match in the XML document.
<xsl:value-of> is used to extract and output the value of a selected element.

Elements used in XSLT Transform:

1. <xsl:stylesheet>: The root element that encapsulates the entire XSLT stylesheet.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

2. <xsl:template>: Defines a template rule that specifies how a particular element or set of elements should be transformed.

<!-- This XSL template is designed to match the root element ("") of the input XML document. -->
<xsl:template match="">
    <html>
        <body>
            <!-- Heading level 2 for the transformed output -->
            <h2>Transformed Output</h2>
        </body>
    </html>
</xsl:template>

3. <xsl:value-of>: Extracts the value of a selected node or expression and includes it in the output.

<!-- This XSL template is designed to match elements with the class "book" in the input XML document. -->
<xsl:template match="book">
    <!-- Div element with the class "book" for styling purposes -->
    <div class="book">
        <!-- Heading level 2 for the book title -->
        <h2><xsl:value-of select="title"/></h2>
        <!-- Paragraph for displaying the author of the book -->
        <p>Author: <xsl:value-of select="author"/></p>
        <!-- Paragraph for displaying the published year of the book -->
        <p>Published Year: <xsl:value-of select="publishedYear"/></p>
    </div>
</xsl:template>

4. <xsl:apply-templates>: Triggers the processing of child nodes using their corresponding templates.

Example: Apply templates to process child nodes.

<!-- This XSL template matches the root element ("") of the input XML document. -->
<xsl:template match="">
    <html>
        <body>
            <!-- Heading level 1 for the transformed content -->
            <h1>Transformed Content</h1>
            <!-- Applying templates to process child elements of the root -->
            <xsl:apply-templates/>
        </body>
    </html>
</xsl:template>

5. <xsl:for-each>: Iterates over a selected set of nodes and applies a template for each item in the node-set.

<!-- xsl:for-each to iterate over 'book' elements -->
<xsl:template match="">
  <html>
    <body>
      <h1>Book List</h1>
      <!-- Use xsl:for-each to iterate over 'book' elements -->
      <xsl:for-each select="library/books/book">
        <div class="book">
          <h2><xsl:value-of select="title"/></h2>
          <p>Author: <xsl:value-of select="author"/></p>
        </div>
      </xsl:for-each>
    </body>
  </html>
</xsl:template>

6. <xsl:if>: Provides conditional processing, allowing certain actions to be taken based on a specified condition.

<!-- xsl:if for conditional processing -->
<xsl:template match="book">
  <div class="book">
    <h2><xsl:value-of select="title"/></h2>
    <p>Author: <xsl:value-of select="author"/></p>
    
    <!-- Use xsl:if to conditionally display a message -->
    <xsl:if test="publishedYear &lt; 2000">
      <p>Older Book</p>
    </xsl:if>
  </div>
</xsl:template>

7. <xsl:choose> and <xsl:when>: Allows multiple conditions to be tested, with different actions taken based on the first condition that evaluates to true.

<!-- xsl:choose and xsl:when for multiple conditions -->
<!-- This XSL template is designed to match elements named "book" in the input XML document. -->
<xsl:template match="book">
    <!-- Styled division for a book with the class "book" -->
    <div class="book">
        <!-- Heading level 2 for the book title -->
        <h2><xsl:value-of select="title"/></h2>
        <!-- Paragraph for displaying the author of the book -->
        <p>Author: <xsl:value-of select="author"/></p>
        
        <!-- xsl:choose to handle multiple conditions based on publishedYear -->
        <xsl:choose>
            <!-- Condition for books published before 2000 -->
            <xsl:when test="publishedYear &lt; 2000">
                <p>Older Book</p>
            </xsl:when>
            <!-- Condition for books published between 2000 and 2010 -->
            <xsl:when test="publishedYear &gt;= 2000 and publishedYear &lt; 2010">
                <p>Published between 2000 and 2010</p>
            </xsl:when>
            <!-- Default condition for recent books -->
            <xsl:otherwise>
                <p>Recent Book</p>
            </xsl:otherwise>
        </xsl:choose>
    </div>
</xsl:template>

8. <xsl:text>: Defines text content to be included in the output.

<!-- xsl:text to output text content -->
<xsl:template match="book">
  <div>
    <h2><xsl:value-of select="title"/></h2>
    <p>Author: <xsl:value-of select="author"/></p>

    <!-- xsl:text to add a line break -->
    <xsl:text>
    </xsl:text>

    <!-- xsl:text to add additional text content -->
    <xsl:text>Published Year: </xsl:text>
    <xsl:value-of select="publishedYear"/>
  </div>
</xsl:template>

9. <xsl:copy>: Copies the current node or a specified node to the output.

<!-- xsl:copy to copy elements -->
<xsl:template match="book">
  <!-- xsl:copy to copy the 'book' element to the output -->
  <xsl:copy>
    <!-- Copy all attributes of the 'book' element -->
    <xsl:copy-of select="@*"/>

    <!-- Add additional elements or modify existing elements if needed -->
    <additionalInfo>Additional Information Here</additionalInfo>

    <!-- Process child nodes of the 'book' element -->
    <xsl:apply-templates/>
  </xsl:copy>
</xsl:template>

10. <xsl:copy-of>: Copies the current node-set or a specified node-set to the output.

<!-- xsl:copy-of to copy nodes -->
<xsl:template match="library">
  <!-- xsl:copy-of to copy all child nodes of 'library' to the output -->
  <xsl:copy-of select="*"/>
</xsl:template>

11. <xsl:message>: Outputs a message to the application or system.

<!-- xsl:message to output messages -->
<xsl:template match="">
  <!-- xsl:message to output a message -->
  <xsl:message>Transformation started!</xsl:message>

  <html>
    <body>
      <h1>Transformed Content</h1>
      <!-- Apply other templates or transformation logic as needed -->
      <xsl:apply-templates/>
    </body>
  </html>

  <!-- xsl:message to output another message -->
  <xsl:message>Transformation completed!</xsl:message>
</xsl:template>

Conclusion

In summary, XSLT transformation serves as a robust mechanism for the stylized presentation of XML data. Proficiency in XSLT enables developers with the ability to convert raw XML data into sophisticated and user-specific outputs. Within the dynamic realm of web development, a distinct comprehension of XSLT has a great significance, serving as an important asset that unlocks a realm of transformative possibilities.

Reffered: https://www.geeksforgeeks.org

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