XSLT eXtensible Stylesheet Language Transformations

1
XSLTeXtensible Stylesheet Language
Transformations

• Advanced Internet Dev COMP 431
• Frank McCown
• Spring 2004
• Modified slides from www.corewebprogramming.com

2
Agenda

• XSLT overview
• Understanding XPath notation
• Processing elements in XSLT templates
• Example

3
XSLT Overview

• W3C technology for transforming an XML document
  into some other text-based form XML, HTML, WML,
  etc.
• XSLT Versions
• XSLT 1.0 (Nov 1999)
• XSLT 2.0 (Nov 2002)
• Official web sitehttp//www.w3c.org/Style/XSL

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eXtensible Stylesheet Language (XSL)

• XSL is a language for expressing stylesheets.
• XSLT
• Transforming XML document
• Xpath
• Expression language used by XSLT to locate
  elements and attributes in an XML doc.
• XSL-FO (Formatting Objects)
• Specifies formatting properties for rendering the
  doc to some other format.

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XSLT Advantages Disadvantages

• Advantages
• Easy display formatted XML data in browser.
• Easier to modify when XML data format changes
  than to modify DOM and SAX parsing code.
• Can be used with database queries that return
  XML.

• Disadvantages
• Memory intensive, performance hit.
• Difficult to implement complex business rules.
• Have to learn new language.

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XSLT Processors

• Apache Xalanhttp//xml.apache.org/xalan
• SAXONhttp//saxon.sourceforge.net
• Microsofts XML Parser 4.0 (MSXML)http//www.micr
  osoft.com/xml

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XSLT and Java

• JDK 1.4 contains all necessary classes
• See javax.xml.transform package.
• Lower versions require downloading XSLT processor
  and SAX parser.

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XML Transformation Example
hello.xml
HTML
hello.xsl
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lt?xml version"1.0" ?gt lt!-- hello.xml
--gt lt?xmlstylesheet type"text/xsl"
href"hello.xsl"?gt ltmyMessagegt ltmessagegtHello
XSLT!lt/messagegt lt/myMessagegt
lthtmlgt ltbodygt lth1gtHello XSLT!lt/h1gt lt/bodygt lt/htmlgt
lt?xml version"1.0" ?gt lt!-- hello.xsl
--gt ltxslstylesheet version"1.0"
xmlnsxsl"http//www.w3.org/1999/XSL/Transform"gt
ltxsltemplate match"myMessage"gt
lthtmlgtltbodygt lth1gtltxslvalue-of
select"message"/gtlt/h1gt lt/bodygtlt/htmlgt
lt/xsltemplategt lt/xslstylesheetgt
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Running Example

• Load hello.xml into IE.
• Run Xalan from the command linejava
  org.apache.xalan.xslt.Process -in hello.xml -xsl
  hello.xsl
• Run our Transform.java from the command line.

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XPath

• XPath is an expression language used to
• Find nodes and attributes (location paths) in the
  XML file
• Test boolean conditions
• Manipulate strings
• Perform numerical calculations

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Location Paths

• Example ltxsltemplate matchentry/address/
  street/gt lt/xsltemplategt
• Can be relative or absolute
• Each step in path separated by / or //
• Evaluated in reference to the current node

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Location Paths (cont.)

• Match root node
• ltxsltemplate match//gt
  lt/xsltemplategt
• Match all children
• ltxsltemplate match/gt
  lt/xsltemplategt

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Location Paths (cont.)

• Match an element
• Use // to indicate zero or more elements may
  occur between slashes
• ltxsltemplate matchentry//street/gt
  lt!-- Match all street elements that are
• grandchildren of entry. --gt
  lt/xsltemplategt
• ltxsltemplate matchorder//item/gt lt!--
  Match all item elements that are
• descendants of order. --gt
• lt/xsltemplategt

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Location Paths (cont.)

• Match a specific element
• Use as a predicate filter to select a
  particular element
• ltxsltemplate matchauthor/namemiddle/gt
  lt!-- Match all name elements that have an
  author
• parent and a middle child. --gt
• lt/xsltemplategt
• ltxsltemplate matchentry/phone1/gt lt!--
  Match the first phone element that is a
• child of entry. --gt
• lt/xsltemplategt

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Location Paths (cont.)

• Match a specific attribute
• Use _at_attribute to select a particular attribute
• ltxsltemplate matchphone_at_location/gt lt!--
  Match all phone elements that have a
• location attribute. --gt
• lt/xsltemplategt
• ltxsltemplate matchcatalog/item_at_id123/gt
  lt!-- Match only item elements with id attribute
• of 123. --gt
• lt/xsltemplategt

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XSLT Stylesheet Elements

• Matching and selection templates
• xsltemplate
• xslapply-templates
• xslvalue-of
• Branching elements
• xslfor-each
• xslif
• xslchoose

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XSLT template Element

• xsltemplate matchXPath
• Defines a template rule for producing output
• Is applied only to nodes that match the pattern
• Invoked by using ltxslapply-templates/gt
• ltxsltemplate match"/"gt
• lthtmlgtltbodygt
• ltxslapply-templates/gt
• lt/bodygtlt/htmlgt
• lt/xsltemplategt
• ltxsltemplate matchname"gt
• Your name is ltxslvalue-of select."/gt
• lt/xsltemplategt

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XSLT value-of Element

• xslvalue-of selectexpression
• Evaluates the expression as a string and outputs
  the result
• Applied only to the first match
• . selects the text value of the current node
• ltname prefixMr.gtJohn Doelt/namegt
• _________________________________________________
  
• ltxsltemplate matchname"gt
• Your name is ltxslvalue-of select_at_prefix"/gt
  ltxslvalue-of select."/gt
• lt/xsltemplategt

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XSLT for-each Element

• xslfor-each selectexpression
• Processes each node selected by the XPath
  expression
• Applied only to the first match
• . selects the text value of the current node
• ltclassgt
• ltstudentgtKim Smithlt/studentgt
• ltstudentgtJack Blacklt/studentgt
• lt/classgt
• _________________________________________________
  ______
• ltxsltemplate matchclass"gt
• ltxslfor-each selectstudent"gt
• ltbgtltxslvalue-of select."/gtlt/bgt
• lt/xslfor-eachgt
• lt/xsltemplategt

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XSLT if Element

• xslif testexpression
• Evaluates the expression and if true applies the
  template
• No if-else, use choose instead
• ltxsltemplate matchclass"gt
• lt!-- Select the first node in the set. --gt
• ltxslif selectposition() first()"gt
• ltbgtltxslvalue-of select."/gtlt/bgt
• lt/xslifgt
• lt/xsltemplategt

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XSLT choose Element

• xslchoose
• Selects any number of alternatives
• Use instead of if-else, or switch statement used
  in other programming languages
• ltxslchoosegt
• ltxslwhen testnot(text())"gt
• Missing value!
• lt/xslwhengt
• ltxslotherwisegt
• ltxslvalue-of select./gt
• lt/xslotherwisegt
• lt/xslchoosegt

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XSLT Functions

• Large set of utility functions
• Examples
• count returns the number of nodes in a node
  setltxslvalue-of select"count(/addressbook/e
  ntry)"/gt
• starts-with returns true if string starts with
  a given characterltxslif test"starts-with(_at_loca
  tion, 'h')"gt Starts with hlt/xslifgt

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Address Book Example
ltaddressbookgt ltentrygt ltname
prefix"Mr."gt Zack Blacklt/namegt ltaddressgt
ltstreetgt101 Main Stlt/streetgt
ltcitygtSearcylt/citygt ltstategtARlt/stategt
ltzipgt12345lt/zipgt lt/addressgt ltphone
location"home" number"501-279-9999" /gt
ltphone location"work" number"501-279-1111"
/gt lt/entrygt ltentrygt ltnamegtJohn
Brownlt/namegt ltphone number"501-305-2222" /gt
lt/entrygt
ltentrygt ltnamegtSusan Whitelt/namegt
ltaddressgt ltstreetgt2000 Center Rdlt/streetgt
ltcitygtDallaslt/citygt ltstategtTXlt/stategt
ltzipgt67790lt/zipgt lt/addressgt ltphone
location"home number"501-279-0000" /gt
lt/entrygt lt/addressbookgt
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lt?xml version"1.0" encoding"ISO-8859-1"?gt ltxsl
stylesheet xmlnsxsl"http//www.w3.org/1999/XS
L/Transform" version"1.0"gt ltxsloutput
method"html"/gt ltxsltemplate
match"/addressbook"gt lthtmlgtltbodygt
lttable border"1"gt ltcaptiongtAddress
Booklt/captiongt lttrgt ltthgtNamelt/thgtltthgtA
ddresslt/thgtltthgtPhone Number(s)lt/thgt lt/trgt
ltxslapply-templates select"entry"/gt
lt/tablegt lt/bodygtlt/htmlgt
lt/xsltemplategt
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ltxsltemplate match"entry"gt lttrgt
lttdgtltxslapply-templates select"name"/gtlt/tdgt
lttdgtltxslapply-templates select"address"/gtlt/tdgt
lttdgtltxslapply-templates select"phone"/gtlt/td
gt lt/trgt lt/xsltemplategt ltxsltemplate
match"name"gt ltxslvalue-of
select"_at_prefix"/gt ltxsltextgt lt/xsltextgt
ltxslvalue-of select"."/gt lt/xsltemplategt
ltxsltemplate match"address"gt ltxslvalue-of
select"street"/gtltbr/gt ltxslvalue-of
select"city"/gt, ltxslvalue-of select"state"/gt
ltxsltextgt lt/xsltextgt ltxslvalue-of
select"zip"/gt lt/xsltemplategt ltxsltemplate
match"phone"gt ltxslvalue-of
select"_at_location"/gt ltxslvalue-of
select"_at_number"/gt ltbr/gt lt/xsltemplategt lt/
xslstylesheetgt
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(No Transcript)
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References

• www.corewebprogramming.com
• www.w3c.org/Style/XSL
• XML How to Program by Deitel

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Esercizio 3

• Scrivere una trasformata XSLT per renderizzare in
  HTML il file XML costruito allesercizio 2.