XSLT Basic

XSLT Tutorial

XSL stands for EXtensible Stylesheet Language, and is a style sheet language for XML documents.
XSLT stands for XSL Transformations. In this tutorial you will learn how to use XSLT to transform XML documents into other formats, like XHTML.

XSL Languages

It Started with XSL

XSL stands for EXtensible Stylesheet Language.

The World Wide Web Consortium (W3C) started to develop XSL because there was a need for an XML-based Stylesheet Language.

CSS = Style Sheets for HTML

HTML uses predefined tags, and the meaning of each tag is well understood.

The <table> tag in HTML defines a table - and a browser knows how to display it.

Adding styles to HTML elements are simple. Telling a browser to display an element in a special font or color, is easy with CSS.

XSL = Style Sheets for XML

XML does not use predefined tags (we can use any tag-names we like), and therefore the meaning of each tag is not well understood.

A <table> tag could mean an HTML table, a piece of furniture, or something else - and a browser does not know how to display it.

XSL describes how the XML document should be displayed!

XSL - More Than a Style Sheet Language

XSL consists of three parts:

XSLT - a language for transforming XML documents
XPath - a language for navigating in XML documents
XSL-FO - a language for formatting XML documents

This Tutorial is About XSLT

The rest of this tutorial is about XSLT - the language for transforming XML documents.

To learn more about XPath and XSL-FO, visit our XPath Tutorial and our XSL-FO Tutorial.

XSLT Introduction

XSLT is a language for transforming XML documents into XHTML documents or to other XML documents.

XPath is a language for navigating in XML documents.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML / XHTML
XML / XML Namespaces
XPath

If you want to study these subjects first, find the tutorials on our Home page.

What is XSLT?

XSLT stands for XSL Transformations
XSLT is the most important part of XSL
XSLT transforms an XML document into another XML document
XSLT uses XPath to navigate in XML documents
XSLT is a W3C Recommendation

XSLT = XSL Transformations

XSLT is the most important part of XSL.

XSLT is used to transform an XML document into another XML document, or another type of document that is recognized by a browser, like HTML and XHTML. Normally XSLT does this by transforming each XML element into an (X)HTML element.

With XSLT you can add/remove elements and attributes to or from the output file. You can also rearrange and sort elements, perform tests and make decisions about which elements to hide and display, and a lot more.

A common way to describe the transformation process is to say that XSLT transforms an XML source-tree into an XML result-tree.

XSLT Uses XPath

XSLT uses XPath to find information in an XML document. XPath is used to navigate through elements and attributes in XML documents.

If you want to study XPath first, please read our XPath Tutorial.

How Does it Work?

In the transformation process, XSLT uses XPath to define parts of the source document that should match one or more predefined templates. When a match is found, XSLT will transform the matching part of the source document into the result document.

XSLT is a W3C Recommendation

XSLT - Transformation

Example study: How to transform XML into XHTML using XSLT.

The details of this example will be explained in the next chapter.

Correct Style Sheet Declaration

The root element that declares the document to be an XSL style sheet is <xsl:stylesheet> or <xsl:transform>.

Note: <xsl:stylesheet> and <xsl:transform> are completely synonymous and either can be used!

The correct way to declare an XSL style sheet according to the W3C XSLT Recommendation is:

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

or:

<xsl:transform version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

To get access to the XSLT elements, attributes and features we must declare the XSLT namespace at the top of the document.

The xmlns:xsl="http://www.w3.org/1999/XSL/Transform" points to the official W3C XSLT namespace. If you use this namespace, you must also include the attribute version="1.0".

Start with a Raw XML Document

We want to transform the following XML document ("cdcatalog.xml") into XHTML:

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>
<cd>
    <title>Empire Burlesque</title>
    <artist>Bob Dylan</artist>
    <country>USA</country>
    <company>Columbia</company>
    <price>10.90</price>
    <year>1985</year>
</cd>
.
.
</catalog>

Create an XSL Style Sheet

Then you create an XSL Style Sheet ("cdcatalog.xsl") with a transformation template:

Link the XSL Style Sheet to the XML Document

Add the XSL style sheet reference to your XML document ("cdcatalog.xml"):

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/xsl" href="cdcatalog.xsl"?>
<catalog>
<cd>
    <title>Empire Burlesque</title>
    <artist>Bob Dylan</artist>
    <country>USA</country>
    <company>Columbia</company>
    <price>10.90</price>
    <year>1985</year>
</cd>
.
.
</catalog>

If you have an XSLT compliant browser it will nicely transform your XML into XHTML.

The details of the example above will be explained in the next chapters.

XSLT <xsl:template> Element

An XSL style sheet consists of one or more set of rules that are called templates.

A template contains rules to apply when a specified node is matched.

The <xsl:template> Element

The <xsl:template> element is used to build templates.

The match attribute is used to associate a template with an XML element. The match attribute can also be used to define a template for the entire XML document. The value of the match attribute is an XPath expression (i.e. match="/" defines the whole document).

Ok, let's look at a simplified version of the XSL file from the previous chapter:

Example

Example Explained

Since an XSL style sheet is an XML document, it always begins with the XML declaration: <?xml version="1.0" encoding="ISO-8859-1"?>.

The next element, <xsl:stylesheet>, defines that this document is an XSLT style sheet document (along with the version number and XSLT namespace attributes).

The <xsl:template> element defines a template. The match="/" attribute associates the template with the root of the XML source document.

The content inside the <xsl:template> element defines some HTML to write to the output.

The last two lines define the end of the template and the end of the style sheet.

The result from this example was a little disappointing, because no data was copied from the XML document to the output. In the next chapter you will learn how to use the <xsl:value-of> element to select values from the XML elements.

XSLT <xsl:value-of> Element

The <xsl:value-of> element is used to extract the value of a selected node.

The <xsl:value-of> Element

The <xsl:value-of> element can be used to extract the value of an XML element and add it to the output stream of the transformation:

Example

Example Explained

Note: The select attribute in the example above, contains an XPath expression. An XPath expression works like navigating a file system; a forward slash (/) selects subdirectories.

The result from the example above was a little disappointing; only one line of data was copied from the XML document to the output. In the next chapter you will learn how to use the <xsl:for-each> element to loop through the XML elements, and display all of the records.

XSLT <xsl:for-each> Element

The <xsl:for-each> element allows you to do looping in XSLT.

The <xsl:for-each> Element

The XSL <xsl:for-each> element can be used to select every XML element of a specified node-set:

Example

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">     // dxu: “/”   match the root element “catalog” <html>
<body>
<h2>My CD Collection</h2>
<table border="1">
    <tr bgcolor="#9acd32">
      <th>Title</th>
      <th>Artist</th>
    </tr>
    <xsl:for-each select="catalog/cd">      //dxu: loop through all “cd” elements of “catalog”.    <tr>
      <td><xsl:value-of select="title"/></td>    //dxu: find the value of element “title”
      <td><xsl:value-of select="artist"/></td>
    </tr>
    </xsl:for-each>
</table>
</body>
</html>
</xsl:template>

</xsl:stylesheet>

Note: The value of the select attribute is an XPath expression. An XPath expression works like navigating a file system; where a forward slash (/) selects subdirectories.

Filtering the Output

We can also filter the output from the XML file by adding a criterion to the select attribute in the <xsl:for-each> element.

<xsl:for-each select="catalog/cd[artist='Bob Dylan']">

Legal filter operators are:

= (equal)
!= (not equal)
< less than
> greater than

Take a look at the adjusted XSL style sheet:

Example

XSLT <xsl:sort> Element

The <xsl:sort> element is used to sort the output.

Where to put the Sort Information

To sort the output, simply add an <xsl:sort> element inside the <xsl:for-each> element in the XSL file:

Example

Note: The select attribute indicates what XML element to sort on.

XSLT <xsl:if> Element

The <xsl:if> element is used to put a conditional test against the content of the XML file.

The <xsl:if> Element

To put a conditional if test against the content of the XML file, add an <xsl:if> element to the XSL document.

Syntax

<xsl:if test="expression">
...some output if the expression is true...
</xsl:if>

Where to Put the <xsl:if> Element

To add a conditional test, add the <xsl:if> element inside the <xsl:for-each> element in the XSL file:

Example

Note: The value of the required test attribute contains the expression to be evaluated.

The code above will only output the title and artist elements of the CDs that has a price that is higher than 10.

XSLT <xsl:choose> Element

The <xsl:choose> element is used in conjunction with <xsl:when> and <xsl:otherwise> to express multiple conditional tests.

The <xsl:choose> Element

Syntax

<xsl:choose>
<xsl:when test="expression">
... some output ...
</xsl:when>
<xsl:otherwise>
... some output ....
</xsl:otherwise>
</xsl:choose>

Where to put the Choose Condition

To insert a multiple conditional test against the XML file, add the <xsl:choose>, <xsl:when>, and <xsl:otherwise> elements to the XSL file:

Example

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
<html>
<body>
<h2>My CD Collection</h2>
<table border="1">
    <tr bgcolor="#9acd32">
      <th>Title</th>
      <th>Artist</th>
    </tr>
    <xsl:for-each select="catalog/cd">
    <tr>
      <td><xsl:value-of select="title"/></td>
      <xsl:choose>
        <xsl:when test="price > 10">
          <td bgcolor="#ff00ff">
          <xsl:value-of select="artist"/></td>
        </xsl:when>
        <xsl:otherwise>
          <td><xsl:value-of select="artist"/></td>
        </xsl:otherwise>
      </xsl:choose>
    </tr>
    </xsl:for-each>
</table>
</body>
</html>
</xsl:template>

</xsl:stylesheet>

The code above will add a pink background-color to the "Artist" column WHEN the price of the CD is higher than 10.

Another Example

Here is another example that contains two <xsl:when> elements:

Example

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
<html>
<body>
<h2>My CD Collection</h2>
<table border="1">
    <tr bgcolor="#9acd32">
      <th>Title</th>
      <th>Artist</th>
    </tr>
    <xsl:for-each select="catalog/cd">
    <tr>
      <td><xsl:value-of select="title"/></td>
      <xsl:choose>
        <xsl:when test="price > 10">
          <td bgcolor="#ff00ff">
          <xsl:value-of select="artist"/></td>
        </xsl:when>
        <xsl:when test="price > 9">
          <td bgcolor="#cccccc">
          <xsl:value-of select="artist"/></td>
        </xsl:when>
        <xsl:otherwise>
          <td><xsl:value-of select="artist"/></td>
        </xsl:otherwise>
      </xsl:choose>
    </tr>
    </xsl:for-each>
</table>
</body>
</html>
</xsl:template>

</xsl:stylesheet>

The code above will add a pink background color to the "Artist" column WHEN the price of the CD is higher than 10, and a grey background-color WHEN the price of the CD is higher than 9 and lower or equal to 10.

XSLT <xsl:apply-templates> Element

The <xsl:apply-templates> element applies a template to the current element or to the current element's child nodes.

The <xsl:apply-templates> Element

The <xsl:apply-templates> element applies a template to the current element or to the current element's child nodes.

If we add a select attribute to the <xsl:apply-templates> element it will process only the child element that matches the value of the attribute. We can use the select attribute to specify the order in which the child nodes are processed.

Look at the following XSL style sheet:

Example

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
<html>
<body>
<h2>My CD Collection</h2>
<xsl:apply-templates/>
</body>
</html>
</xsl:template>

<xsl:template match="cd">
<p>
<xsl:apply-templates select="title"/>
<xsl:apply-templates select="artist"/>
</p>
</xsl:template>

<xsl:template match="title">
Title: <span style="color:#ff0000">
<xsl:value-of select="."/></span>
<br />
</xsl:template>

<xsl:template match="artist">
Artist: <span style="color:#00ff00">
<xsl:value-of select="."/></span>
<br />
</xsl:template>

</xsl:stylesheet>

XSLT Advanced

XSLT - On the Client

If your browser supports it(DXU: XSLT), XSLT can be used to transform the document to XHTML in your browser.

DXU: all three files (XML, XSLT and HTML files are on server, but transform from XML to HTML is done on Client side by Browser via Javascript that is embedded in the HTML file)

A JavaScript Solution

In the previous chapters we have explained how XSLT can be used to transform a document from XML to XHTML. We did this by adding an XSL style sheet to the XML file and let the browser do the transformation.

Even if this works fine, it is not always desirable to include a style sheet reference in an XML file (e.g. it will not work in a non XSLT aware browser.)

A more versatile solution would be to use a JavaScript to do the transformation.

By using a JavaScript, we can:

do browser-specific testing
use different style sheets according to browser and user needs

That is the beauty of XSLT! One of the design goals for XSLT was to make it possible to transform data from one format to another, supporting different browsers and different user needs.

XSLT transformation on the client side is bound to be a major part of the browsers work tasks in the future, as we will see a growth in the specialized browser market (Braille, aural browsers, Web printers, handheld devices, etc.)

The XML File and the XSL File

Look at the XML document that you have seen in the previous chapters:

And the accompanying XSL style sheet:

Notice that the XML file does not have a reference to the XSL file.

IMPORTANT: The above sentence indicates that an XML file could be transformed using many different XSL style sheets.

Transforming XML to XHTML in the Browser

Here is the source code needed to transform the XML file to XHTML on the client:

Example

<html>
<head>
<script>
function loadXMLDoc(dname){
if (window.XMLHttpRequest)
{
xhttp=new XMLHttpRequest();
}
else
{
xhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xhttp.open("GET",dname,false);
xhttp.send("");
return xhttp.responseXML;
}

function displayResult(){
xml=loadXMLDoc("cdcatalog.xml");
xsl=loadXMLDoc("cdcatalog.xsl");// code for IE
if (window.ActiveXObject)
{
ex=xml.transformNode(xsl);
document.getElementById("example").innerHTML=ex;
}
// code for Mozilla, Firefox, Opera, etc.
else if (document.implementation && document.implementation.createDocument)
{
xsltProcessor=new XSLTProcessor();
xsltProcessor.importStylesheet(xsl);
resultDocument = xsltProcessor.transformToFragment(xml,document);
document.getElementById("example").appendChild(resultDocument);
}
}
</script>
</head>
<body onload="displayResult()">
<div id="example" />
</body>
</html>

Tip: If you don't know how to write JavaScript, you can study our JavaScript tutorial.

Example Explained:

The loadXMLDoc() Function

The loadXMLDoc() function is used to load the XML and XSL files.

It checks what kind of browser the user has and loads the file.

The displayResult() Function

This function is used to display the XML file styled by the XSL file.

Load XML and XSL file
Test what kind of browser the user has
If the user has a browser supporting the ActiveX object:

Use the transformNode() method to apply the XSL style sheet to the xml document
Set the body of the current document (id="example") to contain the styled xml document

If the user has a browser that does not support the ActiveX object:

Create a new XSLTProcessor object and import the XSL file to it
Use the transformToFragment() method to apply the XSL style sheet to the xml document
Set the body of the current document (id="example") to contain the styled xml document

XSLT - On the Server

Since not all browsers support XSLT, one solution is to transform the XML to XHTML on the server.

DXU: transform from XML to HTML is done on the server side by ASP pages, which are also

on the server. Basically everything is on server, it’s just a matter of who is doing the transform, by Browser via javascript or by server via ASP.

A Cross Browser Solution

In the previous chapter we explained how XSLT can be used to transform a document from XML to XHTML in the browser. We created a JavaScript that used an XML parser to do the transformation. The JavaScript solution will not work in a browser that doesn't have an XML parser.

To make XML data available to all kind of browsers, we must transform the XML document on the SERVER and send it as XHTML back to the browser.

That's another beauty of XSLT. One of the design goals for XSLT was to make it possible to transform data from one format to another on a server, returning readable data to all kinds of browsers.

The XML File and the XSLT File

Look at the XML document that you have seen in the previous chapters:

And the accompanying XSL style sheet:

<?xml version="1.0" encoding="ISO-8859-1"?

Deyong Xu's blogs

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Tuesday, April 1, 2014

xslt basic

XSLT Basic

XSLT Tutorial

XSL Languages

XSLT <xsl:sort> Element

XSLT <xsl:if> Element

The <xsl:if> Element

Syntax

Where to Put the <xsl:if> Element

Example

XSLT <xsl:choose> Element

The <xsl:choose> Element

Syntax

Where to put the Choose Condition

Example

Another Example

Example

XSLT Advanced

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