 by Thomas Erl |
XML Core Technology |
 |
|
|
Transforming Data with XSLT |
|
| Within just about any application design, there will be a requirement for the format of data to be altered between the time it is first retrieved, to when it reaches its final destination. Because XML provides a clear separation of content, structure and presentation, the output format of an XML document can be completely “transformed”. |
| Unlike with XML schemas, where you have a series of languages to choose from and combine, XML transformation relies on one core standard: XSLT. There aren’t many alternatives, but there are some supplementary technologies that can be used to extend and optimize this part of an architecture. |
|
| XSLT performs the following two primary transformation tasks: |
| 1. The conversion of one XML document type into another. |
|
| 2. The formatting of an XML document into human-readable output, by conversion to a page-description vocabulary. |
|
| For instance, an XSLT style sheet can be used to transform an XML document into an XSL-FO rendition that will ultimately make it suitable for published output, such as a PDF document. Alternatively, XSLT can be used to convert one XML document into another based on a different XML language, such as WML (Wireless Markup Language). |
| Put simply, XSLT allows for the efficient conversion of XML documents into a number of different output formats. The XSLT feature-set facilitates the manipulation, ordering, and filtering of XML document data to provide alternative views and renditions of information for any number of document transformation scenarios. |
| To demonstrate the use of a simple XSLT template, we’ll transform the XML document below into an HTML table. |
SOA: Principles of Service Design by Thomas Erl  An in-depth guide dedicated to service engineering with a thorough exploration of the design principles that comprise the service-orientation design paradigm (including a comparison with object-orientation). 
Service-Oriented Architecture:Concepts, Technology, and Design by Thomas Erl The first "how-to" guide to building SOA, providing coverage of WS-* specifications, .NET and J2EE platforms, and step-by-step processes for service-oriented analysis and design. 
Service-Oriented Architecture:A Field Guide to Integrating XML and Web Services by Thomas Erl The best-selling guide to service-oriented integration, providing hundreds of integration strategies and over sixty best practices. For more information about either book, visit: www.soabooks.com |
About SOA Systems
SOA Systems Inc. provides strategic SOA consulting services and offers a comprehensive SOA training program. For more information see: • www.soasystems.com • www.soatraining.com |
|
<?xml version=”1.0”?> <inventory> <book category=”Fiction”> <title>Joy of Integration</title> <author>Joe Smith</author> </book> <book category=”Non-Fiction”> <title>Integration for Dummies</title> <author>John Doe</author> </book> </inventory> | ||||||
| To the above document we need to add a reference to the XSLT template we’ll be building. | ||||||
| <?xml-stylesheet type="text/xsl" href="book.xsl" ?> | ||||||
| Note that XML documents do not need to have this statement embedded – the linking of an XML document and an XSLT template can be accomplished dynamically at runtime. | ||||||
| The XSLT template begins with the following header statements that simply identifies it as an XML document conforming to the W3C XSLT specification. | ||||||
|
<?xml version="1.0"?> <xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"> | ||||||
| The following construct establishes the base node of the XML document, to which the template applies: | ||||||
|
<xsl:template match="/"> <xsl:apply-templates /> </xsl:template> | ||||||
| The match="/" fragment identifies the root node, which tells the XSLT processor that this template applies to the entire XML document (as opposed to a subset of the document tree). | ||||||
| The construct below uses XPath expressions to locate and loop through each instance of the book element. Every iteration through the loop results in the insertion of a table row consisting of category, title and author column values. | ||||||
|
<xsl:template match="inventory"> <table border="1"> <xsl:for-each select="book"> <tr> <td><xsl:value-of select="@category"/></td> <td><xsl:value-of select="title"/></td> <td><xsl:value-of select="author"/></td> </tr> </xsl:for-each> </table> </xsl:template> | ||||||
| The XSLT syntax is interspersed with HTML tags responsible for building the table. Note the use of the @ symbol, which identifies a value as being an attribute, as opposed to an element. | ||||||
| The XSLT template is completed with the following closing element: | ||||||
| </xsl:transform> | ||||||
| Here is the template in its entirety: | ||||||
|
<?xml version="1.0"?> <xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"> <xsl:template match="/"> <xsl:apply-templates /> </xsl:template> <xsl:template match="inventory"> <table border="1"> <xsl:for-each select="book"> <tr> <td><xsl:value-of select="@category"/></td> <td><xsl:value-of select="title"/></td> <td><xsl:value-of select="author"/></td> </tr> </xsl:for-each> </table> </xsl:template> </xsl:transform> | ||||||
| Upon opening the XML document, the sample template will generate HTML formatted output that a browser should render as follows: | ||||||
|
|
|
|
|
|
|
| Home | Copyright © 1999-2007 SOA Systems Inc. |