xml for e-commerce iii helena ahonen-myka. in this part... n transforming xml n traversing xml n web...
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XML for E-commerce III
Helena Ahonen-Myka
In this part...
Transforming XML Traversing XML Web publishing frameworks
Transforming XML
Extensible Stylesheet Language
a language for transforming XML documents
an XML vocabulary for specifying the formatting of XML documents
XSLT
specifies the conversion of a document from one format to another
XSLT transformation (stylesheet) is a valid XML document
based on hierarchical tree structure mechanism for matching patterns within
the original XML document and applying formatting to that data
XML Path Language (XPath)
a mechanism for referring to the wide variety of element and attribute names and values in an XML document
also non-validated documents have to be able to be transformed: DTD cannot be used to outline the structure
tree-based: specify the path to the element
XPath
specify the part relative to the current element being processed
…or relative to the root: reference an element that is not in the current element’s scope
…or using pattern matching: find an element whose parent is element E and which has a sibling element F
XPath: examples
Match the element named Book relative to the current element:
<xsl:value-of select:”Book” />
XPath: Examples
Match the element named Contents nested within the Book element
<xsl:value-of select=”Book/Contents” />
Match the Contents element using an absolute path:
<xsl:value-of select=”/Book/Contents” />
XPath: examples
Match the focus attribute of the current element:
<xsl:value-of select=”@focus” />
Match the focus attribute of the Chapter element:
<xsl:value-of select=”Chapter/@focus” />
XPath: examples Match any Para element with an Appendix
ancestor element: … select=”Appendix//Para”
id(”W11”) matches the element with unique ID ´W11´
Para[1] matches any Para element that is the first Para child element of its parent
XPath: examples
Para[last()=1] matches any Para element that is the only Para child element of its parent
Items/Item[position()>1] matches any Item element that has an Items parent and that is not the first Item child of its parent
XPath
Because often the input document is not fixed, an Xpath expression can result in the evaluation of no input data, one input element or attribute, or multiple input elements or attributes
the result of evaluating an Xpath expression is referred to as a node set.
XSL stylesheet is an XML document must be well-formed must contain an XML declaration must declare all the namespaces it uses the XSL namespace (prefix xsl:) defines
elements that are needed for performing transformations
Skeleton XSL stylesheet
<?xml version=”1.0” ?>
<xsl:stylesheet
xmlns:xsl=”http://www.w3.org/1999/XSL/Transform”
xmlns:JavaXML=”http://www.oreilly.com/catalog/javaxml/”
version=”1.0”>
</xsl:stylesheet>
XSL Template
locates a particular element or set of elements within the input XML document and applies a rule or set of rules to the resulting XML
<xsl:template match=”[XPath expression]”>
<!-- here are the rules and formatting -->
</xsl:template>
Printing all the data:
<?xml version=”1.0” ?>
<xsl:stylesheet xmlns:xsl=”http://www.w3.org/1999/XSL/Transform”xmlns:JavaXML= ”http://www.oreilly.com/catalog/javaxml/”version=”1.0”>
<xsl:template match=”JavaXML:Book”> <xsl:apply-templates /></xsl:template>
</xsl:stylesheet>
Notes: JavaXML:Book is the root element xsl:apply-templates tells the processor
to match the children of the current element and apply their templates
each element has a default template, which contains xsl:apply-templates and printing the data content
result (prev slide): all the data of the document is printed (unformatted)
Generating HTML
<xsl:template match=”JavaXML:Book”> <html> <head> <title>Here is my HTML page!</title> </head> <body> <xsl:apply-templates /> </body> </html></xsl:template>
HTML Output
<html><head> <title>Here is my HTML page!</title></head> <body> Java and XML
Introduction What Is It? How Do I Use It? ...
</body></html>
xsl:value-of element<xsl:template match=”JavaXML:Book”> <html> <head> <title><xsl:value-of select:”JavaXML:Title” /> </title> </head> <body> <xsl:apply-templates /> </body> </html></xsl:template>
Produces: ...<head><title>Java and XML</title></head>...
Looping and iteration
xsl:for-each
<xsl:template match=”JavaXML:Contents”> <center> <h2>Table of Contents</h2> </center> <hr /> <ul> <xsl:for-each select=”JavaXML:Chapter”> <li><xsl:value-of select=”JavaXML:Heading” /></li> </xsl:for-each> </ul></xsl:template>
Conditional processing: if
xsl:if : nodes that conform to both an XPath expression and some user-defined criteria
only chapters with focus=Java:
<xsl:for-each select=”JavaXML:Chapter”> <xsl:if test=”@focus=’Java’”> <li><xsl:value-of selecct=”JavaXML:Heading” /></li> </xsl:if></xsl:for-each>
Conditional processing: choose
<xsl:for-each select=”JavaXML:Chapter”> <xsl:choose> <xsl:when test=”@focus=’Java’”> <li><xsl:value-of select=”JavaXML:Heading” /> (Java Focus) </li> </xsl:when> <xsl:otherwise> <li><xsl:value-of select=”JavaXML:Heading” /> (XML Focus)</li> </xsl:otherwise> </xsl:choose><xsl:for-each>
Adding elements and attributes
xsl:element, xsl:attribute
<xsl:element name=”myElement”> <xsl:attribute name=”myAttribute”> XML </xsl:attribute> is great!</xsl:element>
Produces: <myElement myAttribute=”XML”>is great!</myElement>
Numbering
<xsl:template match=”items”> <xsl:for-each select=”item”> <xsl:sort select=”.” /> <p> <xsl:number value=”position()” format=”1. ” /> <xsl:value-of select=”.” /> </p> <xsl:for-each></xsl:template>
Sorting
<employees> <employee> <name> <given>James</given> <family>Clark</family> </name> … </employee></employees>
Sorting<xsl:template match=”employees”> <ul> <xsl:apply-templates select=”employee”> <xsl:sort select=”name/family” /> <xsl:sort select=”name/given” /> </xsl:apply-templates> </ul></xsl:template>
<xsl:template match=”employee”> <li> <xsl:value-of select=”name/given” /> <xsl:text> </xsl:text> <xsl:value-of select=”name/family” /> </li></xsl:template>
Copying parts without transforming sometimes a part should be passed as
such, without any transformation assume: JavaXML:Copyright contains
some HTML formatting:
<xsl:template match=”JavaXML:Copyright”> <xsl:copy-of select=”*” /></xsl:template>
Formatting objects (e.g.for PDF)
<xsl:template match=”JavaXML.Title”> <fo:block font-size=”24pt” text-align-last=”centered” space-before.optimum=”24pt”> <xsl:apply-templates> </fo:block></xsl:template>
Produces:
<fo:block font-size=”24pt” text-align=”centered” space-before.optimum=”24pt”> Java and XML </fo:block>
Traversing XML
In transforming documents, random access to an document is needed
SAX cannot look backward or forward difficult to locate siblings and children DOM: access to any part of the tree
DOM
Level 1: navigation of content within a document
Level 2: modules and options for specific content models, such as XML, HTML, and CSS
Level 3
DOM Java bindings
Interfaces and classes that define and implement the DOM
http://www.w3.org/TR/DOM-Level-2/ java-binding.html
bindings often included in the parser implementations (the parser generates a DOM tree)
Parsing using a DOM parser
import org.apache.xerces.parsers.DOMParser;
DOMParser parser = new DOMParser();
parser.parse(uri);
Output is important
the entire document is parsed and added into the output tree, before any processing takes place
handle: org.w3c.dom.Document object = one level above the root element in the document
parser.parse(uri);Document doc = parser.getDocument();
Printing a document
Private static void printTree(Node node) { switch (node.getNodeType()) { case Node.DOCUMENT_NODE: // Print the contents of the Document object break;
case Node.ELEMENT_NODE: // Print the element and its attributes break;
case Node.TEXT_NODE: ...
…the Document node
Case Node.DOCUMENT_NODE: System.out.println(”<xml version=\”1.0\”>\n”); Document doc = (Document)node; printTree(doc.getDocumentElement()); break;
… elementsCase Node.ELEMENT_NODE: String name= node.getNodeName(); System.out.print(”<” + name); // Print out attributes… (see next slide…) System.out.println(”>”);
// recurse on each child NodeList children = node.getChildNodes(); if (children != null) { for (int i=0; i<children.getLength(); i++) { printTree(children.item(i)); } } System.out.println(”</” + name + ”>”);
… and their attributes
case Node.ELEMENT_NODE: String name = node.getNodeName(); System.out.print(”<” + name); NamedNodeMap attributes = node.getAttributes(); for (int i=0; i<attributes.getLength(); i++) { Node current = attributes.item(i); System.out.print(” ” + current.getNodeName() + ”=\”” + current.getNodeValue() + ”\””); } System.out.println(”>”); ...
…textual nodes
case Node.TEXT_NODE:case Node.CDATA_SECTION_NODE: System.out.print(node.getNodeValue()); break;
Web publishing frameworks
See: http://www.oreilly.com/catalog/javaxml/ chapter/ch09.html
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