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Distributed Software Development
XSLT Chris Brooks
Department of Computer ScienceUniversity of San Francisco
Department of Computer Science — University of San Francisco – p. 1/
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9-2:^ XSLT^ •^ XSLT is an XML-based language that allows you to^ declaratively
specify how a document should be changed or transformed.^ ◦^ You specify the output for a particular element; no need tomanage tree traversal. • Useful for:^ ◦^ Emitting an HTML display of an XML document^ ◦^ Converting between tag vocabularies^ ◦^ Extracting plain text from an XML document^ ◦^ AUtomatically modifying or filtering an XML document.
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9-3:^ Output^ •^ You can transform an XML document into:^ ◦^
Plain text ◦ HTML ◦ XML (or any flavor thereof)
Department of Computer Science — University of San Fra
9-4:^ Our CD database
Tomorrow
Never^ Knows
Beatles
Revolver
Rock^
5
2:57^
6 ^ Feb^ ^2005 ...
Department of Computer Science — University of San Francisco – p. 4/
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9-5:^ Step 1: Using XSLT to emit plain text^ •^ To begin, let’s use XSLT to print a plaintext version of ourcatalog.^ •^ We can run XSLT from the command line or within a browser.^ ◦^
/usr/bin/4xslt on lab machines ◦ Most modern browsers have XSLT support ◦ Debugging is easier from the command line
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9-6:^ Step 2: filtering elements^ •^ That’s fine, but pretty dull.^ •^ Let’s select just artist, title, and album to display.^ •^ We do that through the use of apply-templates.^ •^ What if we left out apply-templates in the song template?
Department of Computer Science — University of San Fra
9-7:^ Emitting HTML^ •^ We can also emit other markup languages, such as HTML.(XHTML, actually).^ •^ Just indicate the tags to be produced by a template match.
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9-8:^ Emitting XML^ •^ We can also use XSLT to create new XML documents withdifferent tag names or contents.^ •^ For example, let’s say we want to change the tags to be inSpanish.
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9-9:^ Copying Nodes^ •^ When transforming from XML to XML, often, it’s useful to copysections of a document without changing it.^ •^ copy makes a shallow copy of a node.^ ◦^
Useful if you want to change a bunch of values or attributes. • copy-of makes a deep copy and lets you specify a path. • For example, let’s make a new database with just artist, albumand title.
Department of Computer Science — University of San Fra
9-10:^ Incorporating CSS^ •^ We can still use CSS to control presentational elements.^ •^ With HTML, we can just embed a ’link’ tag in the generatedHTML.
Department of Computer Science — University of San Francisco – p. 10/
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9-11:^ Incorporating CSS^ •^ If we’re emitting XML, we can instead embed a
processing
instruction
into the output document.
-^ Note: this will work best if we do the XSLT on the server side.^
href="songs.css"
type="text/css"
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9-12:^ Referencing a stylesheet from an XML document^ •^ The command line is great for debugging, but much of the time,we want the client to do the work.^ •^ Most web browsers have at least some support for XSLT.^ ◦^
More advanced features are not universally supported. ◦ In particular, the browser’s XSLT processor may make asingle pass and not apply the CSS. (firefox)
Department of Computer Science — University of San Fran
9-19:^ Predicates^ •^ If you need more flexibility in specifying nodes of interest, youcan use a predicate.^ •^ Predicates are contained inside square brackets.^ •^ To be included in final node set, a node must pass both axisand predicate tests.
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9-20:^ Examples^ •^ //song/[id=”s1”]/title/text - text for all ’s1’ songs.^ •^ //song[title] - all quotations that have a source subelement.^ •^ //song[not(source)] - songs that do not have a title sub-element.^ •^ //song[position() == 2] or //song[2] - the second quotation.
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9-21:^ So what’s all this good for?^ •^ XPath is very useful for allowing users to query an XMLdocument.^ •^ Even more useful for specifying which transformations shouldbe applied in an XML document.^ •^ gives us a way to easily specify transformations that shouldtake place based on a node’s context.
Department of Computer Science — University of San Fran
9-22:^ Sorting^ •^ XSLT also has built-in support for sorting and processing yourelements.
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9-23:^ Parameters in XSLT^ •^ You can also pass paramters into an XSLT stylesheet.^ •^ You can also define them at the top of your XSLT program.^ •^ Parameters can be referenced with a $.
...
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9-24:^ Using XSLT from Python !/usr/bin/pythonfrom^ Ft.Xml.Xslt.Processor
import^
Processor
from^ Ft.Xml
import
InputSource xsltproc
=^ Processor(
)
sweaterdata
= InputSource.DefaultFactory.fromUri(’sweater.xml’) sweaterxsl
=^ InputSource.DefaultFactory.fromUri(’sweater.xsl’) xsltproc.appendStylesheet(sweaterxsl)sweaterXML
=^ xsltproc.run(sweaterdata) print^ sweaterXML
Department of Computer Science — University of San Fran
9-25:^ Summary^ •^ XSLT allows you to declaratively specify how a documentshould be transformed.^ •^ Works on the parse tree.^ ◦^
Can emit text or XML • XPath allows you to easily identify nodes. • Makes it easy to have separate representations for storage ornetwor transmission and for display.
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