XSLT Copy Element Example

XSLT, or Extensible Stylesheet Language Transformations, is a powerful language used for transforming XML documents into other formats such as HTML, plain text, or even other XML structures. One of its fundamental capabilities is the ability to manipulate XML elements, including the ability to copy elements from one location to another or to duplicate them. This article will guide you through the concept of copying elements using XSLT, highlighting examples and practical use cases for better understanding.

I. Introduction

A. Definition of XSLT

XSLT is a declarative language designed for transforming XML documents. It utilizes stylesheets written in XML to define how to process and generate data. XSLT allows developers to manipulate data from XML sources, making it possible to convert XML into different formats or structures.

B. Purpose of Copying Elements in XSLT

The ability to copy elements serves various purposes, such as maintaining the structure of an XML document while altering its contents or creating transformed outputs where certain elements are needed multiple times in different contexts. This feature helps in generating dynamic XML structures seamlessly.

II. The xsl:copy Element

A. Overview

The xsl:copy element is a crucial part of XSLT, allowing for the replication of elements from the source XML to the output. It copies the current element along with all its attributes, effectively duplicating any part of an XML document during transformation.

B. Attributes of xsl:copy

Attribute	Description
select	Specifies the node to be copied. If not specified, it copies the current node being processed.
namespace	Used to define the namespace for the copied element.

III. XSLT Copy Example

A. Source XML Document

Let us consider a sample XML document representing a collection of books:


<library>
    <book title="1984" author="George Orwell">
        <publisher>Secker & Warburg</publisher>
        <year>1949</year>
    </book>
    <book title="Brave New World" author="Aldous Huxley">
        <publisher>Chatto & Windus</publisher>
        <year>1932</year>
    </book>
</library>

B. XSLT Stylesheet for Copying Elements

Next, we will create an XSLT stylesheet that copies the entire structure of the library element and its child elements:


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

    <xsl:template match="/library">
        <xsl:copy>
            <xsl:apply-templates select="*"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="*">
        <xsl:copy>
            <xsl:apply-templates select="@*"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="@*">
        <xsl:copy>
            <xsl:value-of select="."/>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

C. Output Result

When applying the above XSLT to our source XML document, the resulting output will look like this:


<library>
    <book title="1984" author="George Orwell">
        <publisher>Secker & Warburg</publisher>
        <year>1949</year>
    </book>
    <book title="Brave New World" author="Aldous Huxley">
        <publisher>Chatto & Windus</publisher>
        <year>1932</year>
    </book>
</library>

IV. Practical Use Cases

A. Use in Transforming XML Data

Using the xsl:copy element allows developers to retain the structure of documents while transforming the data contained in them. For example, if you need to extract certain elements from an XML document and replicate them in another format or structure, xsl:copy is invaluable.

B. Benefits of Using xsl:copy

Preservation of original XML structure.
Easy modification and transformation of data while retaining attributes.
Streamlining complex transformations with minimal code.

V. Conclusion

A. Recap of Key Points

In summary, XSLT is a powerful tool for transforming XML documents, and the xsl:copy element plays a vital role in copying elements and maintaining the integrity of the original structure. By understanding how to apply copying within your XSLT stylesheets, you can effectively manage and transform XML data.

B. Further Reading and Resources

To deepen your understanding of XSLT and copying techniques, consider exploring resources on XML and XSLT specifications, tutorials, or documentation.

FAQ Section

What is XSLT used for?

XSLT is primarily used to transform XML data into different formats, such as HTML for web pages, plain text, or other XML structures.

Can I copy only specific attributes using xsl:copy?

No, the xsl:copy element copies all attributes of the element being replicated. However, you can create templates to control which attributes to copy if necessary.

How does xsl:copy differ from xsl:copy-of?

xsl:copy copies the current node, while xsl:copy-of copies nodes selected by an XPath expression. Use xsl:copy for individual nodes and xsl:copy-of for a set of nodes.

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