CIS 375—Web App Dev II

CIS 375—Web App Dev II XPath

XPath Introduction • What is XPath? • XPath is a syntax for defining parts of an _____ document • XPath uses paths to define XML elements • XPath defines a library of standard __________ • XPath is a major element in XSLT • XPath is not written in XML • XPath is a W3C ____________ • Without XPath knowledge you will not be able to create XSLT documents. • XPath was released as a W3C _______________, November 16, 1999, as a language for addressing parts of an XML document. XML functions Standard Recommendation

XPath Example <?xml version="1.0" encoding="ISO-8859-1"?> <catalog> <cd country="USA"> <title>Empire Burlesque</title> <artist>Bob Dylan</artist> <price>10.90</price> </cd> … • Given the XML code above, the XPath expression /catalog/cd[price>10.80]selects all CD’s with price greater than $10.80. • /catalog/cd/title selects all title elements. • These “elements” are also called ________. nodes

XPath Syntax • The following code makes the corresponding selection • //cd …all CD elements • /catalog/cd/* … all child elements of the CD element • //* … all elements in the document • /catalog/cd[1] … the first CD child element • /catalog/cd[last()] … the last CD child element • /catalog/cd[price] … all CD elements with a price • /catalog/cd[price=10.90]/price … all price elements with a price of $10.90 • /catalog/cd/title | /catalog/cd/artist … all title and artist elements • //cd[@country='UK'] … all CD’s where country=‘UK’

XPath Location Paths • An absolute location path starts with a slash ( / ) and a relative location path does not. • The syntax for a location step is: axisname::nodetest[predicate] • Examples of selection • child::cd … all CD elements that are children of the current node (child: can be omitted from a location step) • cd[position()=1] … first CD child of the current node • cd[@type="classic"] is short forchild::cd[attribute::type="classic"] • ../@src … the src attribute of the parent of the current node

XPath Expressions / Functions • XPath supports expressions. • Numerical: +, -, x, div, _____ • Equality: =, != • Relational: <, <=, >, >= • Boolean: or, and • XPath contains a function library for converting data. • Node set functions: count(), last(), name(), position() • String functions: concat(), string(), substring() • Number functions: ceiling(), round(), sum() • Boolean functions: boolean(), false(), true() mod

XPath Examples • Selecting nodes: http://www.w3schools.com/xpath/tryit.asp?filename=try_xpath_select_cdnodes • Selecting nodes using criteria: http://www.w3schools.com/xpath/tryit.asp?filename=try_xpath_select_pricenodes_high

<?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl= "http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <html> <body> <h2>My CD Collection</h2> <xsl:apply-templates/> </body> </html> </xsl:template> <xsl:template match="cd"> <xsl:apply-templates select="title | artist | price“ /> </xsl:template> <xsl:template match="title"> Title: <xsl:value-of select="."/> </xsl:template> <xsl:template match="artist"> Artist: <xsl:value-of select="."/> </xsl:template> <xsl:template match="price"> 10% discount price: <xsl:value-of select=".*.9“/> </xsl:template> </xsl:stylesheet> A Final XPath Example

Output From Final Example

CIS 375—Web App Dev II