XSL XSLT and XPath Jan 14 2019 What is XSL XSL stands for Extensible Stylesheet Language CSS was designed for styling HTML pages and can be used to style XML pages XSL was designed specifically to style XML pages and is much more sophisticated than CSS XSL consists of three languages XSLT XSL Transformations is a language used to transform XML documents into other kinds of documents most commonly HTML so they can be displayed XPath is a language to select parts of an XML document to transform with XSLT XSL FO XSL Formatting Objects is a replacement for CSS There are no current implementations of XSL FO and we won t cover it 2 How does it work The XML source document is parsed into an XML source tree You use XPath to define templates that match parts of the source tree You use XSLT to transform the matched part and put the transformed information into the result tree The result tree is output as a result document Parts of the source document that are not matched by a template are typically copied unchanged 3 Simple XPath Here s a simple XML document xml version 1 0 library book title XML title author Gregory Brill author book book title Java and XML title author Brett McLaughlin author book library XPath expressions look a lot like paths in a computer file system means the document itself but no specific elements library selects the root element library book selects every book element author selects every author element wherever it occurs 4 Simple XSLT xsl for each select book loops through every book element everywhere in the document xsl value of select title chooses the content of the title element at the current location xsl for each select book xsl value of select title xsl for each chooses the content of the title element for each book in the XML document 5 Using XSL to create HTML Our goal is to turn this xml version 1 0 library book title XML title author Gregory Brill author book book title Java and XML title author Brett McLaughlin author book library Into HTML that displays something like this Book Titles XML Java and XML Book Authors Gregory Brill Brett McLaughlin Note that we ve grouped titles and authors separately 6 What we need to do We need to save our XML into a file let s call it books xml We need to create a file say books xsl that describes how to select elements from books xml and embed them into an HTML page We do this by intermixing the HTML and the XSL in the books xsl file We need to add a line to our books xml file to tell it to refer to books xsl for formatting information 7 books xml revised xml version 1 0 xml stylesheet type text xsl href books xsl library book This tells you where title XML title to find the XSL file author Gregory Brill author book book title Java and XML title author Brett McLaughlin author book library 8 Desired HTML html head title Book Titles and Authors title head Blue text is data extracted body h2 Book titles h2 from the XML document ul li XML li li Java and XML li Brown text is our ul HTML template h2 Book authors h2 ul li Gregory Brill li We don t necessarily li Brett McLaughlin li ul know how much data we body will have html 9 XSL outline 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 html xsl template xsl stylesheet 10 Selecting titles and authors h2 Book titles h2 ul xsl for each select book Notice the li xsl value of select title xsl foreach loop li xsl for each ul h2 Book authors h2 same thing replacing title with author Notice that XSL can rearrange the data the HTML result can present information in a different order than the XML 11 All of books xml xml version 1 0 xml stylesheet type text xsl href books xsl library book title XML title author Gregory Brill author book book title Java and XML title author Brett McLaughlin author book Note if you do View Source library this is what you will see not the resultant HTML 12 All of books xsl xml version 1 0 encoding ISO 88591 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl template match html head title Book Titles and Authors title head body h2 Book titles h2 ul xsl for each select book li xsl value of select title li xsl for each ul h2 Book authors h2 ul xsl for each select book li xsl value of select author li xsl for each ul body html xsl template xsl stylesheet 13 How to use it In a modern browser such as Netscape 6 Internet Explorer 6 or Mozilla 1 0 you can just open the XML file Older browsers will ignore the XSL and just show you the XML contents as continuous text You can use a program such as Xalan MSXML or Saxon to create the HTML as a file This can be done on the server side so that all the client side browser sees is plain HTML The server can create the HTML dynamically from the information currently in XML 14 The result in IE 15 The End 16
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