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- Move site/ Hugo source from gh-pages to main so the workflow can trigger correctly - Fix publish-hugo.yml: now in main, builds and deploys to gh-pages:docs/ via peaceiris/actions-gh-pages - Add 3 new SEO articles: XSLT 3.0 features, beginners guide, template matching - Add llms.txt to blog and frontend so ChatGPT/Gemini can recommend the tool better - Remove stale /site mkdocs ignore rule, add site/public to gitignore instead Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
132 lines
4.2 KiB
Markdown
132 lines
4.2 KiB
Markdown
---
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title: "XSLT for beginners: your first transformation"
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description: "Learn XSLT from scratch with practical examples. Transform XML step by step using templates, match patterns, and value-of."
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date: 2025-02-20T00:00:00Z
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tags: ["beginners", "xslt", "tutorial"]
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---
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XSLT is a language for transforming XML documents into other formats — another XML structure, HTML, plain text, or JSON. If you are new to it, the learning curve can feel steep because XSLT is declarative and template-driven, which is different from procedural languages. This guide walks you through the core ideas with working examples you can run in [XSLT Playground](https://xsltplayground.com) right now.
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## What XSLT does
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You start with an XML source document. You write a stylesheet that describes rules for transforming it. The processor reads both and produces an output document. The stylesheet does not loop through the input line by line — instead, it defines templates that match nodes, and the processor calls those templates as it traverses the document tree.
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## Your first stylesheet
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Start with a simple XML document:
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<catalog>
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<book id="b1">
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<title>Design Patterns</title>
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<author>Gang of Four</author>
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<price>45.00</price>
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</book>
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<book id="b2">
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<title>Clean Code</title>
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<author>Robert Martin</author>
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<price>38.00</price>
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</book>
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</catalog>
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```
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Now write a stylesheet that turns this into an HTML table:
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<xsl:stylesheet version="2.0"
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xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
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<xsl:output method="html" indent="yes"/>
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<xsl:template match="/">
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<html>
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<body>
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<table border="1">
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<tr>
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<th>Title</th>
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<th>Author</th>
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<th>Price</th>
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</tr>
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<xsl:apply-templates select="catalog/book"/>
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</table>
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</body>
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</html>
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</xsl:template>
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<xsl:template match="book">
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<tr>
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<td><xsl:value-of select="title"/></td>
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<td><xsl:value-of select="author"/></td>
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<td><xsl:value-of select="price"/></td>
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</tr>
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</xsl:template>
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</xsl:stylesheet>
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```
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Paste both into [XSLT Playground](https://xsltplayground.com) and run it. You will see an HTML table with the book data.
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## Understanding templates
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The `<xsl:template match="/">` rule fires when the processor reaches the document root. Inside it, `<xsl:apply-templates select="catalog/book"/>` tells the processor to find all `book` elements inside `catalog` and call the matching template for each one.
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The second template `<xsl:template match="book">` fires once per `book` element. Inside it, `<xsl:value-of select="title"/>` extracts the text content of the `title` child.
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This is the core loop of XSLT: match, apply, select.
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## XPath selects nodes
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The `select` and `match` attributes use XPath, a path language for navigating XML trees. A few rules you will use constantly:
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| XPath | Meaning |
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|---|---|
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| `catalog/book` | `book` children of `catalog` |
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| `//book` | All `book` elements anywhere in the document |
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| `book/@id` | The `id` attribute of `book` |
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| `book[price > 40]` | Books whose price exceeds 40 |
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| `.` | The current node |
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| `..` | The parent of the current node |
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## Filtering with predicates
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Add a predicate to the `apply-templates` call to show only books over 40:
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```xml
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<xsl:apply-templates select="catalog/book[price > 40]"/>
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```
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Or use `xsl:if` inside the template:
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```xml
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<xsl:template match="book">
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<xsl:if test="price > 40">
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<tr>
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<td><xsl:value-of select="title"/></td>
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</tr>
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</xsl:if>
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</xsl:template>
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```
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## Sorting output
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Use `xsl:sort` to control the order:
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```xml
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<xsl:apply-templates select="catalog/book">
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<xsl:sort select="price" data-type="number" order="ascending"/>
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</xsl:apply-templates>
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```
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## What to try next
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Once you are comfortable with templates and XPath:
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- Learn `xsl:for-each` for inline iteration
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- Explore `xsl:choose` for multi-branch conditionals
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- Try `xsl:variable` to store intermediate values
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- Look at `xsl:param` to pass values into your stylesheet from outside
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All of these work in XSLT 1.0, 2.0, and 3.0. The [XSLT Playground](https://xsltplayground.com) lets you set the version and experiment without installing anything.
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