extensible stylesheet language (xsl)

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XSLXSL is a standard that consists of three parts:XPath (navigation in documents)

XPath was taught in the DB course, so it will not be taught

XSLT (transformation of documents)XSLFO (FO for formatting objects)

This is a rather complex language for typesetting (i.e., preparing text for printing)

It will not be taught

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XSLTXSLT is a language for transforming XML

documents into other XML documentsFor example, XHTML, RSS, KML, GML,

MathML, WMLCan also transform XML to text documents,

e.g., SQL programsAn XSLT program is itself an XML document

(called an XSL stylesheet) that describes the transformation process for input documents

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Text

WML

DTD

XSLT Processors

XML

XSL

XSLT Processor

XHTML

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Web PageWeb Page

LayoutLayout

Doc. Doc. StructureStructure

DataData

Web Pages – The Whole Picture

XMLXML

XSLXSL

XHTMLXHTML

StyleStyle

KnowledgeKnowledge

CSSCSS

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<?xml version="1.0" encoding="ISO-8859-1"?><catalog> <cd country="UK"> <title>Dark Side of the Moon</title> <artist>Pink Floyd</artist> <price>10.90</price> </cd> <cd country="UK"> <title>Space Oddity</title> <artist>David Bowie</artist> <price>9.90</price> </cd> <cd country="USA"> <title>Aretha: Lady Soul</title> <artist>Aretha Franklin</artist> <price>9.90</price> </cd> </catalog>

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<?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> <head><title>cd catalog</title></head> <body><h1>This is a cd catalog!</h1></body> </html> </xsl:template></xsl:stylesheet>

Valid XML!Commands are XML elements

with the namespace xslIncludes XHTML elements

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Applying XSL Stylesheets to XMLThere are several ways of applying an XSL stylesheet to an XML document:Directly applying an XSLT processor to the XML

document and the XSL stylesheetCalling an XSLT processor from within a programAdding to the XML document a link to the XSL

stylesheet and letting the browser do the transformation

The resulting XHTML document is shown instead of the original XML

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Processing XSL in JavaYou can use the XALAN package of Apache in order to process XSL transformations

java org.apache.xalan.xslt.Process -IN myXmlFile.xml -XSL myXslFile.xsl -OUT myOutputFile.html

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How Does XSLT Work?An XSL stylesheet is a collection of templates that

are applied to source nodes (i.e., nodes of the given XML)

Each template has a match attribute that specifies to which source nodes the template can be applied

Each source node has at a template that matches itThe current source node is processed by applying a

template that matches this nodeWhen processing a node, it is possible (but not

necessary) to recursively process other nodes, e.g., the children of the processed node

The XSLT processor processes the document root (/)

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TemplatesA template has the form

<xsl:template match="pattern"> ...</xsl:template>

The content of a template consists of XML elements (e.g., XHTML) and text that are

copied to the resultXSL elements (<xsl:…>) that are actually

instructionsThe pattern syntax is a subset of XPath

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<?xml version="1.0" encoding="ISO-8859-1"?><?xml-stylesheet type="text/xsl"

href="catalog1.xsl"?><catalog> <cd country="UK"> <title>Dark Side of the Moon</title> <artist>Pink Floyd</artist> <price>10.90</price> </cd> <cd country="UK"> <title>Space Oddity</title> <artist>David Bowie</artist> <price>9.90</price> </cd> <cd country="USA"> <title>Aretha: Lady Soul</title> <artist>Aretha Franklin</artist> <price>9.90</price> </cd> </catalog> catalog1.xml

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The Result<html> <head> <META http-equiv="Content-Type" content="text/html;

charset=UTF-8"> <title>cd catalog</title> </head> <body> <h1>This is a cd catalog!</h1> </body></html>

In XALAN, automatically added to <head>

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Examples of Match Attributesmatch="cd",

All elements with tag name cd

match="//cd", match="/catalog/cd/artist"All matches of the absolute XPath

match="cd/artist"All artist nodes that have a cd parent

match="catalog//artist"All artist nodes that have a catalog ancestor

match="cd[@country='UK']/artist"

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Processing starts by applying a template to the root If no specified template matches the root, then

one is inserted by default (see the next slide)The XSL stylesheet must specify explicitly

whether templates should be applied to descendants of a node

It is done by putting inside a template the instruction:

<xsl:apply-templates select="xpath"/>In xpath, the current processed node is used as

the context nodeWithout the select attribute, this

instruction processes all the children of the current node (including text nodes)

<xsl:apply-templates><xsl:apply-templates>

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Default TemplatesXSL provides implicit built-in templates

that match every element and text nodes

Templates we write always override these built-in templates (when they match)

<xsl:template match="/|*"><xsl:apply-templates/>

</xsl:template>

<xsl:template match="text()|@*"><xsl:value-of select="."/>

</xsl:template>

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

<?xml version="1.0" encoding="UTF-8"?> Dark Side of the Moon Pink Floyd 10.90 Space Oddity David Bowie 9.90 Aretha: Lady Soul Aretha Franklin 9.90

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In XALAN and in IE (it yields an empty page in Firefox)

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<?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="cd"> <h2>A cd!</h2> </xsl:template></xsl:stylesheet>

<h2>A cd!</h2> <h2>A cd!</h2> <h2>A cd!</h2>

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<?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="cd[@country='UK']"> <h2>A cd!</h2></xsl:template></xsl:stylesheet>

<h2>A cd!</h2> <h2>A cd!</h2> Aretha: Lady Soul Aretha Franklin9.90

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<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:apply-templates select="catalog/cd[@country='UK']/artist"/> </xsl:template> <xsl:template match="artist"> <h2>An artist!</h2> </xsl:template></xsl:stylesheet>

<h2>An artist!</h2> <h2>An artist!</h2>

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<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:apply-templates select="cd[@country='UK']/artist"/> </xsl:template> <xsl:template match="artist"> <h2>An artist!</h2> </xsl:template></xsl:stylesheet>

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<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:apply-templates mode=“first” select="catalog/cd[@country='UK']/artist"/> <xsl:apply-templates mode=“second” select="catalog/cd[@country='UK']/artist"/> </xsl:template>

<xsl:template mode=“first” match="artist"> <h2>An artist!</h2> </xsl:template> <xsl:template mode=“second” match="artist"> <h2>The artist is coming back!</h2> </xsl:template></xsl:stylesheet>

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The Most Frequently Used Elements of XSL<xsl:value-of select="xpath"/>

This element extracts the value of a node from the nodelist located by xpath

<xsl:for-each select="xpath"/>This element loops over all the nodes in the

node list located by xpath

<xsl:if test="cond"/>, <xsl:if test="xpath"/>, etc.This element is for conditional processing

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<?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><head><title>cd catalog</title></head> <body> <h1>CD catalog</h1> <ul> <xsl:for-each select="catalog/cd">

<li><xsl:value-of select="title"/> [<xsl:value-of select="artist"/>]</li> </xsl:for-each> </ul></body></html> </xsl:template></xsl:stylesheet>

Currently selected element is the context (current) node

Example 1


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<li><xsl:apply-templates select="."/></li> </xsl:for-each> </ul></body></html> </xsl:template>

Example 2


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<xsl:template match="cd"> <b><xsl:value-of select="artist"/></b>: <xsl:value-of select="title"/> <xsl:if test="price<10"> (<em>now on sale: $<xsl:value-of select="price"/> </em>) </xsl:if> </xsl:template></xsl:stylesheet>

Example 2 (cont.)

Entities replace characters price<10 → price<10

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<xsl:choose> <xsl:when test="price < 9"> (<em>Special price!</em>) </xsl:when> <xsl:when test="price>9 and price<=10"> (<i>Good price!</i>) </xsl:when> <xsl:otherwise> (Normal price.) </xsl:otherwise></xsl:choose>

Example 3

<xsl:choose>:

Switch syntax for conditions

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The <xsl:sort> ElementThe <xsl:sort> element is used to sort the

list of nodes that are looped over by the <xsl:for-each> element

Thus, the <xsl:sort> must appear inside the <xsl:for-each> element

The looping is done in sorted order

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<xsl:sort select="title"/> <li><xsl:value-of select="title"/></li> </xsl:for-each> </ul></body></html> </xsl:template></xsl:stylesheet>

CDs are iterated in ascending order of the titles


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Setting Values in AttributesThe <xsl:value-of> element cannot be used

within attribute valueHowever, we can insert expressions into

attribute values, by putting the expression inside curly braces ({})

Alternatively, we can use <xsl:element> in order to construct XML elements

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An ExampleIn the following example, we add to each

CD entitled t a link to the URL /showcd.jsp?title=t

<xsl:template match="cd"> <b><xsl:value-of select="artist"/></b>: <a href="/showcd.jsp?title={./title}">

<xsl:value-of select="title"/> </a>

</xsl:template>

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Using <xsl:element>

<xsl:template match="cd"> <b><xsl:value-of select="artist"/></b>: <xsl:element name="a"> <xsl:attribute name="href"> /showcd.jsp?title=<xsl:value-of select="title"/> </xsl:attribute> <xsl:value-of select="title"/> </xsl:element> </xsl:template>

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On XSL CodeTypically, an XSLT program can be written in

several, very different waysTemplates can sometime replace loops and

vice versaConditions can sometimes be replaced with

XPath predicates (e.g., in the select attribute) and vice versa

A matter of convenience and elegancy

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On Recursive TemplatesIt is not always possible to avoid recursive

templatesThat is, use only the template of the root

Suppose that we want to write an XSL stylesheet that generates a copy of the source documentIt is rather easy to do it when the structure of the

source XML document is knownCan we write an XSL stylesheet that does it for

every possible XML document?Yes! (see next slide)

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

<xsl:output method="xml"/>

<xsl:template match="*"> <xsl:element name="{name()}"> <xsl:for-each select="@*"> <xsl:attribute name="{name()}"> <xsl:value-of select="."/> </xsl:attribute> </xsl:for-each> <xsl:apply-templates/> </xsl:element> </xsl:template>

</xsl:stylesheet>

Identity TransformationStylesheet

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Generating Valid XHTMLBy default, the documents that XSL

stylesheets generate are not valid XHTMLNext, we will show how XSL stylesheet can

be changed in order to generate valid XHTML

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The Original XSL Example

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<html> <head> <META http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>cd catalog</title> </head> <body> <h1>This is a cd catalog!</h1> </body></html>

Uppercase tag name, unclosed element

No DOCTYPE

The Original Transformation Result

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<?xml version="1.0" encoding="ISO-8859-1"?><xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml"> <xsl:output method="html" doctype-public="-//W3C//DTD XHTML 1.0 Strict//EN"

doctype-system= "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"/> <xsl:template match="/"> …

Modifying the XSL Example

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>cd catalog</title> </head> <body> <h1>This is a cd catalog!</h1> </body></html> META is not inserted

The Transformation Result

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Some Other XSL ElementsThe <xsl:text> element inserts free text in

the outputThe <xsl:copy-of select="xpath"> creates

a copy of the specified nodes (deep copy, i.e., copies the entire subtree)

The <xsl:copy select="xpath"> creates a copy of the specified nodes (does not copy children or attributes)

The <xsl:comment> element creates a comment node in the result tree

The <xsl:variable> element defines a variable (local or global) that can be used within the program

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ExampleTransform this list of number to be

SortedAlternatingly red and blue

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Example of Using a Variable

Using Variables and FunctionsUsing names, templates can be called

directly and serve as functionsIt is possible to use variables and function in

XSL to perform computationsReturned values of functions can be set to

variables<xsl:variable name=“v"> <xsl:call-template name=“f"> <xsl:with-param name=“n" select=“3"/> </xsl:call-template></xsl:variable>

v=f(3)

Computing Fibonacci Numbers

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

<?xml-stylesheet type="text/xsl" href="fib.xsl"?>

<val>8

</val>

Given value

Style sheet

<?xml version="1.0"?><xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:template name="fib"> <xsl:param name="n"/> <xsl:choose> <xsl:when test="$n < 2"> <xsl:value-of select="1"/> </xsl:when> <xsl:otherwise> <xsl:variable name="f1"> <xsl:call-template name="fib"> <xsl:with-param name="n" select="$n -1"/>

</xsl:call-template> </xsl:variable> <xsl:variable name="f2"> <xsl:call-template name="fib"> <xsl:with-param name="n" select="$n -2"/>

</xsl:call-template> </xsl:variable> <xsl:value-of select="$f1+$f2"/> </xsl:otherwise> </xsl:choose></xsl:template>

if n<=2 return 1

f1=fib(n-1)

f2=fib(n-2)

return f1+f2

<xsl:template match="/"> <html><head><title>Fibonacci</title></head> <body> <xsl:variable name="val"> <xsl:value-of select="/val"/> </xsl:variable> The Fibonacci number at position <xsl:value-of select="$val"/> is <xsl:call-template name="fib"> <xsl:with-param name="n" select="$val"/> </xsl:call-template> </body> </html> </xsl:template></xsl:stylesheet>

val = the value in <val> </val>

return fib(val)

Transforming XML to XHTML, in the BrowserUse JavaScriptCheck what is the current browser before

applying the transformation (different browsers use a slightly different DOM)

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<html> <head> <script> function loadXMLDoc(fname) { var xmlDoc; // code for IE if (window.ActiveXObject) { xmlDoc=new ActiveXObject("Microsoft.XMLDOM"); }

// code for Mozilla, Firefox, Opera, etc. else if (document.implementation && document.implementation.createDocument) { xmlDoc=document.implementation.createDocument("","",null); } else { alert('Your browser cannot handle this script'); } xmlDoc.async=true; xmlDoc.load(fname); return(xmlDoc); }

XML to XHTML in Browser

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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 id="example" onLoad="displayResult()"> </body> </html>

XML to XHTML in Browser

Applying Xalan from Java ProgramsThe following example illustrate how to apply

Xalan on a given XML and XSL from within a Java program

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// Instantiate a DocumentBuilderFactory. javax.xml.parsers.DocumentBuilderFactory dfactory = javax.xml.parsers.DocumentBuilderFactory.newInstance();

// Use the DocumentBuilderFactory to provide access to a DocumentBuilder. javax.xml.parsers.DocumentBuilder dBuilder = dfactory.newDocumentBuilder();

// Use the DocumentBuilder to parse the XML input. org.w3c.dom.Document inDoc = dBuilder.parse("foo.xml");

1. Generate a document builder

2. Parse the XML document

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// Generate a Transformer. javax.xml.transform.Transformer transformer

= tFactory.newTransformer(new javax.xml.transform.stream.StreamSource("foo.xsl")); // Create an empy DOMResult object for the output. javax.xml.transform.dom.DOMResult domResult = new javax.xml.transform.dom.DOMResult(); // Perform the transformation. transformer.transform(new javax.xml.transform.dom.DOMSource(inDoc), domResult); // Now you can get the output Node from the DOMResult. org.w3c.dom.Node node = domResult.getNode();

1. Generate a transformer2. Create an empty DOM

result3. Apply the transformation4. Get the output node

transformer.transform(new DOMSource(inDoc), new StreamResult(new FileOutputStream(“result.html")));

To produce HTML,replace

LinksW3C Recommendation:

http://www.w3.org/TR/xslthttp://www.xml.com/pub/a/2000/08/holman/

index.htmlhttp://www.w3schools.com/xsl/default.asphttp://xml.apache.org/xalan-j/apidocs/

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extensible stylesheet language (xsl)

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