XSLT Developer¶

Last Updated: May 2026 | Version: 1.10.0

Note (Phase 10c): The standalone XSLT Developer tab has been retired. Its capabilities now live in the Unified Shell's Transform panel (stylesheet, input, output method, parameters, XPath/XQuery) together with the advanced tools in the panel's ⋮ (overflow) menu — Debug XSLT… (the interactive debugger with breakpoints, step, variables, call stack, watch), Batch Transform…, Profile run, and Trace run. Open the Transform panel from the Transform icon in the activity bar; results appear in the OUTPUT panel docked below the editor. The feature description below is retained for reference; the controls now live in the Unified Shell rather than a dedicated tab.

The XSLT Developer is a full-featured development environment for creating and testing XSLT stylesheets and XQuery scripts. It includes live transformation, parameter support, batch processing, and debugging tools.

Overview¶

XSLT Developer Overview The XSLT Developer with editors, parameters, and result panels

The XSLT Developer provides:

Full code editors for XML, XSLT, and XQuery
Live Transform mode for instant feedback
XSLT Parameters for reusable stylesheets
Multi-file batch processing using XQuery
Performance metrics and debugging
Favorites integration for quick access

Interface Layout¶

Left Panel: Input Editors¶

The left panel contains tabbed editors for your source files:

Tab	Description
XML Source	The XML document to transform
XSLT Stylesheet	Your XSLT transformation code
XQuery Script	XQuery code for queries and transformations
Parameters	Define parameters to pass to XSLT

Right Panel: Results¶

Tab	Description
Result	The transformation output
Live Preview	Real-time HTML rendering
Performance	Execution metrics and statistics
Debug	Messages, warnings, and execution trace

Button	Shortcut	Description
Open XML	-	Load an XML source file
Transform	F5 or Ctrl+R	Execute the transformation
Live	Ctrl+L	Toggle live transform mode
Add Favorite	Ctrl+D	Save current file to favorites
Favorites	Ctrl+Shift+D	Show/hide favorites panel
Help	F1	Open help

Getting Started¶

Step 1: Load Your Files¶

Click Open XML in the toolbar to load your source XML
Switch to the XSLT Stylesheet tab
Click Open to load an XSLT file, or type directly in the editor

Step 2: Transform¶

Click Transform (or press F5) to run the transformation.

Step 3: View Results¶

The output appears in the Result tab. For HTML output, switch to Live Preview to see the rendered page.

Live Transform Mode¶

Enable Live Transform to automatically re-run the transformation whenever you make changes to the XML, XSLT, or XQuery.

Click the Live button in the toolbar (or press Ctrl+L)
The button highlights when live mode is active
Make changes to any input - results update automatically

This is ideal for developing and debugging stylesheets.

Using XSLT Parameters¶

XSLT stylesheets can accept parameters to make them more flexible. The Parameters tab lets you define these values.

Defining Parameters in XSLT¶

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

  <!-- Define a parameter with a default value -->
  <xsl:param name="title" select="'Default Title'"/>
  <xsl:param name="show-prices" select="true()"/>
  <xsl:param name="currency" select="'EUR'"/>

  <xsl:template match="/">
    <html>
      <head><title><xsl:value-of select="$title"/></title></head>
      <body>
        <h1><xsl:value-of select="$title"/></h1>
        <xsl:if test="$show-prices">
          <!-- Show prices in the specified currency -->
        </xsl:if>
      </body>
    </html>
  </xsl:template>

</xsl:stylesheet>

Setting Parameter Values¶

Switch to the Parameters tab
Click Add to create a new parameter
Enter the parameter name (e.g., title)
Enter the value (e.g., My Custom Report)
Select the type: String, Number, or Boolean

Parameters are passed to the XSLT processor during transformation.

XQuery Development¶

The XQuery Script tab provides a full XQuery editor. XQuery is powerful for querying and transforming XML data.

Basic XQuery Example¶

for $book in /books/book
where $book/price > 30
order by $book/title
return <result>{$book/title}</result>

Built-in XQuery Examples¶

Click the Examples button to insert sample queries:

Example	Description
Simple Query	Basic element selection
FLWOR Expression	For-Let-Where-Order-Return
HTML Report	Generate HTML output
Data Quality Check	Validate data completeness

Multi-File Batch Processing¶

Process multiple XML files at once using XQuery and the collection() function.

Switching to Batch Mode¶

In the XML Source tab, select Multiple Files (Batch)
The interface changes to show a file list

Adding Files¶

Action	Description
Add Files	Select individual XML files
Add Directory	Add all XML files from a folder
Remove Selected	Remove checked files from the list
Clear All	Remove all files
Select All	Check/uncheck all files

Writing XQuery for Batch Processing¶

Use collection() to access all selected files:

Example 1: List All Root Elements

for $doc in collection()
return $doc/*/local-name()

Example 2: Extract Data from All Files

for $doc in collection()
for $order in $doc//order
return <result>
  <file>{document-uri($doc)}</file>
  <orderId>{$order/@id/string()}</orderId>
  <total>{$order/total/string()}</total>
</result>

Example 3: Count Elements Across Files

<summary>
  <totalFiles>{count(collection())}</totalFiles>
  <totalOrders>{count(collection()//order)}</totalOrders>
</summary>

Example 4: Find Files with Specific Content

for $doc in collection()
where $doc//status = "pending"
return document-uri($doc)

Example 5: Aggregate Data

<report>
  <totalAmount>{sum(collection()//amount)}</totalAmount>
  <averageValue>{avg(collection()//value)}</averageValue>
  <fileCount>{count(collection())}</fileCount>
</report>

Viewing Batch Results¶

After processing, choose how to view results:

Mode	Description
Combined	All results merged together
Per File	Select individual file results from dropdown

Saving Batch Results¶

Save - Save the combined output as a single file
Save All - Save each file's result separately with _result suffix

XSLT 3.0 Examples¶

FreeXmlToolkit supports XSLT 3.0 via Saxon HE. Here are some advanced patterns:

For-Each-Group (XSLT 2.0/3.0)¶

Group items without the Muenchian method:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="html" indent="yes"/>

  <xsl:template match="/">
    <html>
      <body>
        <h1>Books by Author</h1>
        <xsl:for-each-group select="books/book" group-by="author">
          <xsl:sort select="current-grouping-key()"/>
          <h2><xsl:value-of select="current-grouping-key()"/></h2>
          <ul>
            <xsl:for-each select="current-group()">
              <li><xsl:value-of select="title"/></li>
            </xsl:for-each>
          </ul>
        </xsl:for-each-group>
      </body>
    </html>
  </xsl:template>

</xsl:stylesheet>

Using Maps and Arrays (XSLT 3.0)¶

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:map="http://www.w3.org/2005/xpath-functions/map">

  <xsl:output method="text"/>

  <xsl:variable name="config" select="map {
    'title': 'Report',
    'format': 'detailed',
    'max-items': 100
  }"/>

  <xsl:template match="/">
    <xsl:text>Title: </xsl:text>
    <xsl:value-of select="map:get($config, 'title')"/>
  </xsl:template>

</xsl:stylesheet>

JSON Output (XSLT 3.0)¶

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="json" indent="yes"/>

  <xsl:template match="/">
    <xsl:map>
      <xsl:map-entry key="'books'">
        <xsl:array>
          <xsl:for-each select="books/book">
            <xsl:map>
              <xsl:map-entry key="'title'" select="string(title)"/>
              <xsl:map-entry key="'author'" select="string(author)"/>
              <xsl:map-entry key="'price'" select="number(price)"/>
            </xsl:map>
          </xsl:for-each>
        </xsl:array>
      </xsl:map-entry>
    </xsl:map>
  </xsl:template>

</xsl:stylesheet>

Text Value Templates (XSLT 3.0)¶

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                expand-text="yes">

  <xsl:output method="html" indent="yes"/>

  <xsl:template match="/">
    <html>
      <body>
        <xsl:for-each select="books/book">
          <p>{title} by {author} - ${price}</p>
        </xsl:for-each>
      </body>
    </html>
  </xsl:template>

</xsl:stylesheet>

Performance Tab¶

Monitor transformation performance:

Metric	Description
Execution Time	Total transformation time in milliseconds
Compilation Time	Time to compile the XSLT stylesheet
Memory Usage	Memory consumed during transformation
Output Size	Size of the generated output

The XSLT Features Used list shows which XSLT features were detected in your stylesheet.

Debug Tab¶

Use debugging features to troubleshoot transformations:

Messages & Warnings¶

Shows all <xsl:message> output and Saxon warnings.

<xsl:message>Processing book: <xsl:value-of select="title"/></xsl:message>

Template Execution Trace¶

Enable Debug Mode to see the sequence of template calls.

Tips for Debugging¶

Use <xsl:message> to output debug information
Check the Debug tab for warnings about unused variables or templates
Enable Debug Mode for detailed execution trace
Click Clear to reset the debug output

Interactive Live Debugger¶

The XSLT Developer includes a full interactive debugger that lets you pause a transformation, step through your stylesheet, and inspect state - similar to debugging in an IDE.

Setting Breakpoints¶

Click the slot in the editor's left margin (gutter) next to a line to toggle a red breakpoint.
Or place the caret on a line and press F9 (the Breakpoint toolbar button).
The Breakpoints panel lists every breakpoint with an enable/disable checkbox and a delete button. Double-click an entry to jump to that line.

Step Controls¶

The debug toolbar provides standard execution controls:

Control	Shortcut	Description
Run-Debug	F5	Start a debug run from the beginning
Continue	F8	Resume until the next breakpoint
Pause	-	Pause at the next instruction (best-effort on Saxon HE)
Step Into	F7	Step into the current instruction
Step Over	F10	Execute the current instruction without descending
Step Out	Shift+F11	Run until the current template/function returns
Stop	-	Terminate the debug session

A green arrow in the gutter marks the line currently executing; a hit breakpoint shows a yellow arrow over the red circle.

Inspecting State¶

When execution is paused, four panels show the live state of the transformation:

Panel	Shows
Variables	Name, value, type, and scope (global/local) of every visible variable, plus the context item
Call Stack	Active template/function frames with file name and line; double-click a frame to jump to it
Watch Expressions	Custom XPath expressions you add to monitor specific values
Breakpoints	All breakpoints, persisted across sessions

Output Options¶

Configure the transformation output:

Option	Values	Description
Output Format	XML, HTML, Text, JSON	The expected output format
Encoding	UTF-8, ISO-8859-1, etc.	Character encoding for output
Indent Output	On/Off	Pretty-print the output

Keyboard Shortcuts¶

Shortcut	Action
F5	Execute transformation
Ctrl+R	Execute transformation
Ctrl+L	Toggle live transform
Ctrl+D	Add to favorites
Ctrl+Shift+D	Show/hide favorites
Ctrl+Shift+C	Copy result
Ctrl+Alt+S	Save result
F1	Help

XQuery Examples¶

Data Extraction¶

(: Extract all customer emails :)
for $customer in /customers/customer
return <email>{$customer/email/text()}</email>

Transformation¶

(: Transform to HTML table :)
<table>
  <tr><th>Name</th><th>Email</th></tr>
  {
    for $c in /customers/customer
    return <tr>
      <td>{$c/name/text()}</td>
      <td>{$c/email/text()}</td>
    </tr>
  }
</table>

Aggregation¶

(: Calculate statistics :)
let $orders := /orders/order
return <stats>
  <count>{count($orders)}</count>
  <total>{sum($orders/amount)}</total>
  <average>{avg($orders/amount)}</average>
  <min>{min($orders/amount)}</min>
  <max>{max($orders/amount)}</max>
</stats>

Conditional Logic¶

(: Categorize items :)
for $item in /items/item
return <categorized>
  <name>{$item/name/text()}</name>
  <category>{
    if ($item/price > 100) then "Premium"
    else if ($item/price > 50) then "Standard"
    else "Budget"
  }</category>
</categorized>

Tips¶

Start with Live Mode off for large files to avoid slow updates
Use the Examples menu to insert working XQuery templates
Check Performance tab if transformations are slow
Save your work to favorites for quick access later
Use batch mode for processing multiple files efficiently
Enable Debug Mode when troubleshooting complex stylesheets
Only process trusted stylesheets - see Security Features for details on XSLT extension security

Troubleshooting¶

Problem	Solution
No output	Check that XML and XSLT/XQuery are both loaded
Syntax error	Check the Debug tab for error details
Slow transformation	Check Performance tab; consider simplifying
Batch results empty	Ensure files are selected (checkboxes checked)
Parameters not working	Verify parameter names match exactly
Java extension function not found	Java extensions are disabled by default for security. See Security Features

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