Introductionto xslt

2
Introduction to XSLT
Agenda
The X* Ecosystem (XSL, XPath, XQuery...)
XML Refresh/Terminology
XPath: Addresses for XML documents
XSLT Basics: template and value-of
XSLT Loops: apply-templates and for-each
XSLT Decisions: if and choose
XSLT Variables: variable and param
XSLT Extras: sort, copy-of, document…
Why/When XSLT?

3
The X* Ecosystem
• XSL(T): Extensible Stylesheet Language
(Transforms)
– Like a giant function with a domain of XML and a
range of XML, HTML and Text
– XSL-FO (Formatting Objects) is a related,
graphics/print-oriented language
• XPath: XML Path (addressing)
– Like a filesystem path in an XML document
– Also like RegEx
– a language for navigating in XML documents

4
XML Nodes
 Processing instruction: <?pi ... ?>
 Element: <element /> or
<element></element>
 Attribute: <element attribute="value" />
 Comment: 
 Entity: &
 Text node (just plain text)

5
XML Syntax Rules
 Escape < > & (turn them into entities <
> &)
 Every document has exactly one root element
 Attribute values are always quoted
 Elements are case-sensitive (and are typically
lowercase)
 You don't have to put an xml processing
instruction at the top of your document

6
XPath: Addresses for XML
XPath Expressions
/library
/library/book
/library/book/@name
/library/book[@name="The
Fourth Civilization"]
/library/book[1]
//book[2]
<library>
<book name="C++ How to
Program" />
<book name="The Fourth
Civilization"
/>
</library>

7
XPath Expressions
/library
/library/book
/library/book/@name
/library/book[1]
//book[2]
<library>
Program" />
Civilization"
/>
</library>

8
XPath Expressions
/library
/library/book
/library/book/@name
/library/book[1]
//book[2]
<library>
Program" />
Civilization"
/>
</library>

9
XPath Expressions
/library
/library/book
/library/book/@name
/library/book
[@name="The Fourth
Civilization"]
/library/book[1]
//book[2]
<library>
Program" />
Civilization"
/>
</library>

10
XPath Expressions
/library
/library/book
/library/book/@name
/library/book[1]
//book[2]
<library>
Program" />
Civilization"
/>
</library>

11
XPath Expressions
/library
/library/book
/library/book/@name
/library/book[1]
//book[2]
<library>
Program" />
Civilization"
/>
</library>

12
XPath Node
selectors
/library/*
/library/book[1]/text()
/library/node()[1]
.
<library>

<book>The Principles of
Computer
Hardware</book>
Civilization"
/>
</library>

13
XPath Node
selectors
/library/*
/library/node()[1]
.
<library>

Computer
Hardware</book>
Civilization"
/>
</library>

14
XPath Node
selectors
/library/*
/library/node()[1]
.
<library>

Computer
Hardware</book>
Civilization"
/>
</library>

15
XPath Node
selectors
/library/*
/library/node()[1]
.
<library>

Computer
Hardware</book>
Civilization"
/>
</library>

16
XPath Axes
/library/child::book
(or /library/book for short)
/descendent-or-self::book
(or //book for short)
//book[1]/parent::*
(or //book[1]/.. for short)
//book[2]/preceding-
sibling::book
//book[1]/attribute::name
(or //book[1]/@name for
short)
<library>
Program" />
Civilization"
/>
</library>

17
XPath Axes
/descendent-or-
self::book
//book[1]/parent::*
sibling::book
short)
<library>
Program" />
Civilization"
/>
</library>

18
XPath Axes
//book[1]/parent::*
sibling::book
short)
<library>
Program" />
Civilization"
/>
</library>

19
XPath Axes
//book[1]/parent::*
sibling::book
short)
<library>
Program" />
Civilization"
/>
</library>

20
XPath Axes
//book[1]/parent::*
sibling::book
//book[1]/
attribute::name
short)
<library>
Program" />
Civilization"
/>
</library>

21
XPath Functions
//book[last()]
count(//book)
name(/*)
//book[contains(@name,
"C++")]
//book[not(contains(
@name, "C++"))]
<library>
Program" />
Civilization"
/>
</library>

22
XPath Functions
//book[last()]
count(//book)
name(/*)
"C++")]
@name, "C++"))]
Returns: 2
<library>
Program" />
Civilization"
/>
</library>

23
XPath Functions
//book[last()]
count(//book)
name(/*)
"C++")]
@name, "C++"))]
Returns: "library"
<library>
Program" />
Civilization"
/>
</library>

24
XPath Functions
//book[last()]
count(//book)
name(/*)
//book[contains(
@name, "C++")]
@name, "C++"))]
<library>
Program" />
Civilization"
/>
</library>

25
XPath Functions
//book[last()]
count(//book)
name(/*)
"C++")]
@name, "C++"))]
<library>
Program" />
Civilization"
/>
</library>

26
Other Useful XPath Functions
position() – provides the position in a list (nice for numbering a
sequence of nodes)
sum(xpath) – takes a sequence of nodes and adds up their
numerical values – see also avg(), min(), max()
concat(string, string, …) – exactly what you think
string-length(string) – returns the number of characters
substring(string, start[, length]) – the first char is at 1
translate(source-string, find-string, replace-string) – looks
for individual chars and replaces them
Example: translate("ABCD", "BD", "bd")  "AbCd"

27
XPath Operators
//book[last() or
contains(@name,
"C++")]
//book[string-
length(@name) > 5]
//book[1] | //book[2]
Other operators:
and, =, >, <=, >=, !=, +,
-, *, div, mod
Don't forget to escape < >!
<library>
Program" />
Civilization"
/>
</library>

28
XPath Operators
//book[last() or
contains(@name,
"C++")]
//book[string-
length(@name) > 5]
//book[1] | //book[2]
Other operators:
and, =, >, <=, >=, !=, +,
-, *, div, mod
<library>
Program" />
Civilization"
/>
</library>

29
XPath Operators
//book[last() or
contains(@name,
"C++")]
//book[string-
length(@name) > 5]
//book[1] | //book[2]
Other operators:
and, =, >, <=, >=, !=, +,
-, *, div, mod
<library>
Program" />
Civilization"
/>
</library>

30
XPath Operators
//book[last() or
contains(@name,
"C++")]
//book[string-
length(@name) > 5]
//book[1] | //book[2]
Other operators:
and, =, >, <=, >=, !=,
+, -, *, div, mod
<library>
Program" />
Civilization"
/>
</library>

31
XSLT Basics
• Try it out
– Make an XML file
– Make an XSLT file
– Run the transform and
view the transformed
data
<xml />
input
<xsl:… />
transform
<xml />
(or text)
output

• <xsl:template> Element
– It details what items from the source document it should
handle and uses its content to specify what should be added to
the output when it is executed
– match attribute is used to associate a template with an XML
element and define a template for the entire document. E.g
emptyXSL.xsl
• <xsl:value-of> Element
– used to evaluate an expression and add the result to the
output
– used to extract the value of an XML element and add it to the
output stream of the transformation
• <xsl:for-each> Element
– used to select every XML element of a specified node-set
• <xsl:apply-templates> Element
– responsible for deciding which items in the source document
should be processed; they are then handled by the appropriate
template

33
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
<quote>...one giant leap for
mankind.</quote>
</person>
Sample Output
Neil Armstrong said "...one giant
leap for mankind."
Sample XSLT
<xsl:stylesheet version="1.0" xmlns:xsl=
"http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" />
<xsl:template match="/person">
<xsl:value-of select="concat(
name/@first, ' ', name/@last)"
/>
said "
<xsl:value-of select="quote" />"
</xsl:template>
</xsl:stylesheet>

34
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind.</quote>
</person>
Sample Output
leap for mankind."
Sample XSLT
/>
said "
</xsl:template>
</xsl:stylesheet>

35
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind.</quote>
</person>
Sample Output
leap for mankind."
Sample XSLT
/>
said "
</xsl:template>
</xsl:stylesheet>

36
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
Sample Output
<html><head><title>Neil
Armstrong</title>
</head>
<body><blockquote>…one giant
leap for mankind.</blockquote>
</body></html>
Sample XSLT  HTML
<xsl:output method="html" />
<html><head><title>
name/@first, ' ', name/@last)" />
</title></head><body>
<blockquote><xsl:value-of
select="quote" /></blockquote>
</body></html>
</xsl:template>
</xsl:stylesheet>

37
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
Sample Output
<html><head><title>Neil
Armstrong</title>
</head>
<body><blockquote>…one giant
leap for mankind.</blockquote>
</body></html>
<html><head><title>
name/@first, ' ', name/@last)" />
</title></head><body>
<blockquote><xsl:value-of
select="quote" /> </blockquote>
</body></html>
</xsl:template>
</xsl:stylesheet>

38
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
Sample Output
<quote><speaker firstname="Neil"
lastname="Armstrong"/>
<text>…one giant leap for
mankind.</text>
</quote>
Sample XSLT  XML
<xsl:output method="xml" />
<quote><speaker
firstname="{name/@first}"
lastname="{name/@last}"/>
<text><xsl:value-of select="quote"
/></text>
</quote>
</xsl:template>
</xsl:stylesheet>

39
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
Sample Output
mankind.</text>
</quote>
Sample XSLT  XML
<quote><speaker
/></text>
</quote>
</xsl:template>
</xsl:stylesheet>

40
XSLT Basics
Sample XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
Sample Output
mankind.</text>
</quote>
Sample XSLT  XML
<quote><speaker
/></text>
</quote>
</xsl:template>
</xsl:stylesheet>

41
XSLT Loops: for-each
Sample XML
<zoo>
<birds>
<albatross pop="4" />
<buzzard pop="2" />
<chickadee pop="12" />
</birds>
<mammals>
<aardvark pop="5" />
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
<xsl:template match="/zoo">
<html><head><title>Zoo</title>
</head><body>
<xsl:for-each select="*">
<h1>
<xsl:value-of select="name(.)" />
</h1>
</xsl:for-each>
</body></html>
</xsl:template>
</xsl:stylesheet>

42
Sample XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
</head><body>
<h1>
birds
</h1>
<h1>
mammals
</h1>
</body></html>

43
Sample XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
</head><body>
<h1><xsl:value-of select="name(.)" /></h1>
<ul><xsl:for-each select="*">
<li><xsl:value-of select="name(.)" />
(<xsl:value-of select="@pop">)</li>
</xsl:for-each></ul>
</xsl:for-each>
</body></html>
</xsl:template>
</xsl:stylesheet>

44
Sample XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
</head><body>
<h1>birds</h1>
<ul>
<li>albatross (4)</li>
…
</ul>
<h1>mammals</h1>
<ul>
<li>aardvark (5)</li>
…
</ul>
</body></html>

45
XSLT Loops: apply-templates
<xsl:template
match="birds | mammals">
<h1><xsl:value-of select="name(.)"
/></h1>
<ul>
<li><xsl:value-of
select="name(.)" />
(<xsl:value-of
select="@pop"/>)</li>
</xsl:for-each>
</ul>
</xsl:template>
</xsl:stylesheet>
Sample XSLT
<html>
<head><title>Zoo</title></head>
<body>
<xsl:apply-templates
select="*" />
</body>
</html>
</xsl:template>

46
XSLT Decisions: if
XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
XSLT
…
<xsl:template match="birds | mammals">
<h1><xsl:value-of select="name(.)" /> </h1>
<p>We have more than 2...</p>
<xsl:if test="*[@pop > 2]">
<ul>
<xsl:for-each select="*[@pop > 2]">
<li><xsl:value-of select="name(.)" /></li>
</xsl:for-each>
</ul>
</xsl:if>
</xsl:template>
…

47
XSLT Decisions: if
Sample XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
<html><head><title>Zoo</title></head><body>
<h1>birds</h1>
<ul>
<li>albatross</li>
<li>chickadee</li>
</ul>
<h1>mammals</h1>
<ul>
<li>aardvark</li>
<li>bat</li>
</ul>
</body></html>

48
XSLT Decisions: choose
XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
XSLT fragment
(<xsl:choose>
<xsl:when test="@pop = 2">a
couple</xsl:when>
<xsl:when test="@pop <= 5">a
few</xsl:when>
<xsl:otherwise>many</xsl:otherwise>
</xsl:choose>)
</li>
</xsl:template>

49
XSLT Decisions: choose
Sample XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
<ul>
<li>albatross (a few)</li>
<li>buzzard (a couple)</li>
<li>chickadee (many)</li>
</ul>
<ul>
<li>aardvark (a few)</li>
<li>bat (many)</li>
<li>cheetah (a couple)</li>
</ul>
</body></html>

50
XSLT Variables: variable
XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
XSLT fragment
<xsl:variable name="total-animals"
select="sum(*/@pop)" />
(<xsl:value-of select="round(100 * @pop div
$total-animals)"/>% of all <xsl:value-of
select="name(..)"/>)
</li>
</xsl:template>

51
XSLT Variables: variable
Source XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
<ul>
<li>albatross (22% of all birds)</li>
<li>buzzard (11% of all birds)</li>
<li>chickadee (67% of all birds)</li>
</ul>
<ul>
<li>aardvark (2% of all mammals)</li>
<li>bat (97% of all mammals)</li>
<li>cheetah (1% of all mammals)</li>
</ul>
</body></html>

52
XSLT Variables: parameter
<xsl:template name="animal">
<xsl:param name="total" />
<li>
(<xsl:value-of select="round(100 *
@pop div $total)"/>%)
</li>
</xsl:template>
XSLT fragments
<xsl:template match="birds |
mammals">
<xsl:variable name="total-
animals" select="sum(*/@pop)"
/>
<xsl:call-template
name="animal">
<xsl:with-param name="total"
value="$total-animals">
</xsl:call-template>
</xsl:template>

53
XSLT Variables: param
<xsl:template name="animal">
<xsl:param name="total" />
<li>
(<xsl:value-of select="round(100 *
@pop div $total)"/>%)
</li>
</xsl:template>
XSLT fragments
<xsl:template match="birds |
mammals">
<xsl:variable name="total-
animals" select="sum(*/@pop)"
/>
<xsl:call-template
name="animal">
<xsl:with-param
name="total" value="$total-
animals">
</xsl:call-template>
</xsl:template>

54
XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
XSLT fragment
<xsl:param name="minimum-population" select="5" />
<ul>
<xsl:for-each select="*[@pop >= $minimum-
population]">
(<xsl:value-of select="@pop"/>)
</li>
</xsl:template>

55
Source XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
<ul>
<li>chickadee (12)</li>
</ul>
<ul>
<li>bat (200)</li>
</ul>
</body></html>

56
XSLT Extras: sort
XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
XSLT fragment
<ul>
<xsl:sort select="@pop" order="descending" data-
type="number" />
(<xsl:value-of select="@pop"/>)
</li>
</xsl:template>

57
XSLT Extras: sort
Source XML
<zoo>
<birds>
<buzzard pop="2" />
</birds>
<mammals>
<bat pop="200" />
<cheetah pop="2" />
</mammals>
</zoo>
Result HTML
<ul>
<li>chickadee (12)</li>
<li>albatross (4)</li>
<li>buzzard (2)</li>
</ul>
<ul>
<li>bat (200)</li>
<li>cheetah (2)</li>
</ul>
</body></html>

58
XSLT Extras: copy-of
Source XML
<person>
<name first="Neil"
last="Armstrong" />
mankind. </quote>
</person>
XML Output
<quote><name first="Neil"
last="Armstrong"/> <text>…one
giant leap for mankind.</text>
</quote>
Sample XSLT  XML
<quote><xsl:copy-of select="name"
/>
/></text>
</quote>
</xsl:template>
</xsl:stylesheet>

59
XSLT Extras: more elements
• xsl:text – writes literal text to the output
(useful for controlling whitespace or forcing
exact, unescaped output)
• xsl:processing-instruction – writes a PI like
<?php… ?> or <?xml-stylesheet… ?> to the
output
• xsl:import and xsl:include – used to combine
stylesheets (useful for XSLT libraries)

60
XSLT Extras: more functions
• document(url) – opens an XML document at the
given location, returning its nodes as data that
can be used by the template
Example:
document('zoo.xml')/zoo//*[@pop = 2]
• current() – similar to "." except that it always
refers to the current node, even when used inside
predicates
Example:
//*[@pop = current()/@pop]

61
XSLT Extras: xml-stylesheet
To make an XML document show itself in a
transformed format, add this to the top:
<?xml-stylesheet type="text/xsl"
href="path/to/transform.xslt" ?>
This is particularly useful for XML like RSS

62
Why/When XSLT?
 Web Standard
 XSLT v 1.0 Recommended by W3C almost 10
years ago (it's stable and well understood)
 Dozens of implementations and host
languages (Java, .NET, PHP, C++…)
 Wide tool support (Firefox, IE, Visual Studio,
many text editors, full IDEs…)
 No vendor lock-in

63
Why/When XSLT?
Very good at converting XML to XML,
XHTML/HTML, or plain text
 Makes it easy to keep things well-formed
 Uses XML syntax, so the only real new syntax
is XPath (which is also used elsewhere)
 XPath is far more compact than similar DOM
code in JS/Java/C#/etc.
 Can be interpreted (for quick development)
or compiled (for maximum performance)

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