Introduction to XSLT - PowerPoint PPT Presentation

Presentation Transcript

Orion Ifland

2008-05-15

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?

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

The X* Ecosystem

XQuery / XPath 2.0 / XSLT 2.0

Kind of jumbled together
XQuery looks more like a mix of XSLT, SQL, and Javascript (including lots of XPath)‏

XMLNS (XML Namespaces)‏

Like programming language namespaces, distinguishes between elements/attributes with the same name
Used by XSLT and many other XML dialects

XML Nodes

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

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

XPath: Addresses for XML

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[@name="The Fourth Civilization"]

/library/book[1]

//book[2]

</library>

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[1]

//book[2]

</library>

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[1]

//book[2]

</library>

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[1]

//book[2]

</library>

Predicate

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[1]

//book[2]

</library>

XPath Expressions

/library

/library/book

/library/book/@name

/library/book[1]

//book[2]

</library>

XPath Node selectors

/library/*

/library/book[1]/text()

/library/node()[1]

.

<book>The Principles of Computer Hardware</book>

</library>

/library/*

/library/node()[1]

.

<book>ThePrinciples of Computer Hardware</book>

</library>

/library/*

/library/node()[1]

.

</library>

/library/*

/library/node()[1]

.

</library>

Selects the "current" node

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>

XPath Axes

/descendent-or-self::book(or //book for short)

</library>

XPath Axes

</library>

XPath Axes

</library>

XPath Axes

/descendent-or-self::book(or //book for short)‏

</library>

XPath Functions

//book[last()]

count(//book)

name(/*)

//book[contains(@name, "C++")]

//book[not(contains(@name, "C++"))]

</library>

XPath Functions

//book[last()]

count(//book)

name(/*)

Returns: 2

</library>

XPath Functions

//book[last()]

count(//book)

name(/*)

Returns: "library"

</library>

XPath Functions

//book[last()]

count(//book)

name(/*)

</library>

XPath Functions

//book[last()]

count(//book)

name(/*)

</library>

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 themExample: translate("ABCD", "BD", "bd")  "AbCd"

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>

XPath Operators

//book[1] | //book[2]

Other operators:

and, =, >, <=, >=, !=, +, -, *, div, mod

</library>

XPath Operators

//book[1] | //book[2]

Other operators:

and, =, >, <=, >=, !=, +, -, *, div, mod

</library>

XPath Operators

//book[1] | //book[2]

Other operators:

and, =, >, <=, >=, !=, +, -, *, div, mod

</library>

Try it out

Make an XML file

Make an XSLT file

Run the transform and view the transformed data

XSLT Basics

<xml />

input

<xsl:… />

transform

<xml />

(or text)

output

Sample XML

<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>

XSLT Basics

Sample XML

</person>

Sample Output

Sample XSLT

said "

<xsl:value-of select="quote" />"

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

</person>

Sample Output

Sample XSLT

said "

<xsl:value-of select="quote"/>"

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

<quote>...one giant leap for 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" />

</title></head><body>

</body></html>

</xsl:template>

</xsl:stylesheet>

XSLT Basics

All well-formed

Sample XML

</person>

Sample Output

<html><head><title>Neil Armstrong</title></head>

<body><blockquote>…one giant leap for mankind.</blockquote>

</body></html>

</title></head><body>

</body></html>

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

</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>

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

</person>

Sample Output

</quote>

Sample XSLT  XML

</quote>

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

</person>

Sample Output

</quote>

Sample XSLT  XML

</quote>

</xsl:template>

</xsl:stylesheet>

XSLT Basics

Sample XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

<xsl:template match="/zoo">

<xsl:for-each select="*">

<h1>

<xsl:value-of select="name(.)" />

</h1>

</xsl:for-each>

</body></html>

</xsl:template>

</xsl:stylesheet>

XSLT Loops: for-each

Sample XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

Result HTML

<h1>

birds

</h1>

<h1>

mammals

</h1>

</body></html>

Sample XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

</xsl:for-each></ul>

</xsl:for-each>

</body></html>

</xsl:template>

</xsl:stylesheet>

Sample XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

Result HTML

<h1>birds</h1>

<ul>

<li>albatross (4)</li>

…

</ul>

<h1>mammals</h1>

<ul>

<li>aardvark (5)</li>

…

</ul>

</body></html>

<xsl:template match="birds | mammals">

<ul>

</xsl:for-each>

</ul>

</xsl:template>

</xsl:stylesheet>

XSLT Loops: apply-templates

Sample XSLT

<html>

<body>

<xsl:apply-templates select="*" />

</body>

</html>

</xsl:template>

XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

XSLT

…

<xsl:if test="*[@pop > 2]">

<ul>

<xsl:for-each select="*[@pop > 2]">

</xsl:for-each>

</ul>

</xsl:if>

</xsl:template>

…

XSLT Decisions: if

Sample XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

Result HTML

<h1>birds</h1>

<ul>

<li>albatross</li>

<li>chickadee</li>

</ul>

<h1>mammals</h1>

<ul>

<li>aardvark</li>

</ul>

</body></html>

XSLT Decisions: if

XML

<zoo>

<birds>

</birds>

</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>

XSLT Decisions: choose

Sample XML

<zoo>

<birds>

</birds>

</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>cheetah (a couple)</li>

</ul>

</body></html>

XSLT Decisions: choose

XML

<zoo>

<birds>

</birds>

</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>

XSLT Variables: variable

Source XML

<zoo>

<birds>

</birds>

</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>

XSLT Variables: variable

<xsl:template name="animal">

<xsl:param name="total" />

<li>

<xsl:value-of select="name(.)" /> (<xsl:value-of select="round(100 * @pop div $total)"/>%)

</li>

</xsl:template>

XSLT Variables: parameter

XSLT fragments

<xsl:call-template name="animal">

<xsl:with-param name="total" value="$total-animals">

</xsl:call-template>

</xsl:template>

<xsl:template name="animal">

<xsl:param name="total" />

<li>

<xsl:value-of select="name(.)" /> (<xsl:value-of select="round(100 * @pop div $total)"/>%)

</li>

</xsl:template>

XSLT Variables: param

XSLT fragments

<xsl:call-template name="animal">

<xsl:with-param name="total" value="$total-animals">

</xsl:call-template>

</xsl:template>

XML

<zoo>

<birds>

</birds>

</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>

Source XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

Result HTML

<ul>

<li>chickadee (12)</li>

</ul>

<ul>

</ul>

</body></html>

XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

XSLT fragment

<ul>

<xsl:sort select="@pop" order="descending" data-type="number" />

(<xsl:value-of select="@pop"/>)

</li>

</xsl:template>

XSLT Extras: sort

Source XML

<zoo>

<birds>

</birds>

</mammals>

</zoo>

Result HTML

<ul>

<li>chickadee (12)</li>

<li>albatross (4)</li>

<li>buzzard (2)</li>

</ul>

<ul>

<li>cheetah (2)</li>

</ul>

</body></html>

XSLT Extras: sort

Source XML

</person>

XML Output

<quote><name first="Neil" last="Armstrong"/> <text>…one giant leap for mankind.</text>

</quote>

Sample XSLT  XML

</quote>

</xsl:template>

</xsl:stylesheet>

XSLT Extras: copy-of

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)

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 templateExample: document('zoo.xml')/zoo//*[@pop = 2]
current() – similar to "." except that it always refers to the current node, even when used inside predicatesExample://*[@pop = current()/@pop]

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

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

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)

Questions, Demos, Dialog…Introduction to XSLT

Introduction to XSLT - PowerPoint PPT Presentation

PowerPoint Slideshow about 'Introduction to XSLT' - RexAlvis