16.3 Multiple Result Trees
| In the last chapter, you used the saxon:output extension element to create more than one result tree from a single stylesheet. XSLT 2.0 has integrated this functionality into the mainstream of the specification with the result-document element. The following example shows you how to use this element to produce three result trees from one source tree. Example 16-1, the document functions.xml in examples/ch16, describes the new context-related functions from XPath 2.0. Example 16-1. A document describing XPath 2.0 functions<?xml version="1.0"?> <functions type="context"> <function> <name>fn:context-item( )</name> <description>Returns the context item.</description> </function> <function> <name>fn:position( )</name> <description>Returns the position of the context item within the sequence of items currently being processed.</description> </function> <function> <name>fn:last( )</name> <description>Returns the number of items in the sequence of items currently being processed.</description> </function> <function> <name>fn:current-dateTime( )</name> <description>Returns the current xs:dateTime.</description> </function> <function> <name>fn:current-date( )</name> <description>Returns the current xs:date.</description> </function> <function> <name>fn:current-time( )</name> <description>Returns the current xs:time.</description> </function> <function> <name>fn:default-collation( )</name> <description>Returns the value of the default collation property from the static context.</description> </function> <function> <name>fn:implicit-timezone( )</name> <description>Returns the value of the implicit timezone property from the evaluation context.</description> </function> </functions> The descriptions of the functions are from the specification. The fn:position( ) and fn:last( ) functions are the same as the position( ) and last( ) functions from XPath 1.0. The fn:context-item( ) function is similar to the current( ) function available from XSLT 1.0 and XSLT 2.0. Usually, a context item is the same as the current item, except when a predicate is involved.
Example 16-2, the context.xsl stylesheet, produces four result trees based on functions.xml. The default result tree is text, and the three others are for XML, HTML, and XHTML output, respectively. Example 16-2. An XSLT 2.0 stylesheet that produces four kinds of output<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="text"/> <xsl:output name="xml" method="xml" indent="yes"/> <xsl:output name="html" method="html" indent="yes"/> <xsl:output name="xhtml" method="html" indent="yes"/> <xsl:param name="dir">file:///C:/LearningXSLT/examples/ch16</xsl:param> <xsl:template match="functions"> <xsl:text>XPath 2.0 Context Functions </xsl:text> <xsl:text>Date: </xsl:text> <xsl:value-of select="current-date( )"/> <xsl:text> </xsl:text> <xsl:apply-templates select="function" mode="text"/> <xsl:result-document format="xml" href="{$dir}/context.xml"> <xsl:message terminate="no">Printing text result tree...</xsl:message> <list> <description>XPath 2.0 Context Functions</description> <date><xsl:value-of select="current-date( )"/></date> <xsl:message terminate="no">Printing XML result tree in functions.xml...</xsl:message> <xsl:apply-templates select="function" mode="xml"/> </list> </xsl:result-document> <xsl:result-document format="html" href="{$dir}/context.html"> <xsl:message terminate="no">Printing HTML result tree in functions.html...</xsl:message> <html> <body> <h2>XPath 2.0 Context Functions</h2> <h3>Date: <xsl:value-of select="current-date( )"/></h3> <ul> <xsl:apply-templates select="function" mode="html"/> </ul> </body> </html> </xsl:result-document> <xsl:result-document format="xhtml" href="{$dir}/context-x.html"> <xsl:message terminate="no">Printing XHTML result tree in functions-x.html...</xsl:message> <html xmlns="http://www.w3.org/1999/xhtml"> <body> <h2>XPath 2.0 Context Functions</h2> <h3>Date: <xsl:value-of select="current-date( )"/></h3> <ol> <xsl:apply-templates select="function" mode="xhtml"/> </ol> </body> </html> </xsl:result-document> </xsl:template> <xsl:template match="function" mode="text"> <xsl:text> - </xsl:text> <xsl:value-of select="name"/> <xsl:text> </xsl:text> </xsl:template> <xsl:template match="function" mode="xml"> <function><xsl:value-of select="name"/></function> </xsl:template> <xsl:template match="function" mode="html"> <li><xsl:value-of select="name"/></li> </xsl:template> <xsl:template match="function" mode="xhtml"> <li xmlns="http://www.w3.org/1999/xhtml"><xsl:value-of select="name"/></li> </xsl:template> </xsl:stylesheet> The version attribute on stylesheet shows the 2.0 version number. There are four output elements, three of which are named. This allows a result-document element to reference an output element by name, hence to use the information in it. A global parameter named dir holds the name of the directory where three of the result trees are written as files. This information is referenced by the attribute value template {$dir} in the href attributes on the result-document elements. You could pass in a new value for the dir parameter if you want to change the destination of the output. The template matching functions creates a text result tree, plus three other result trees inside result-document elements. Each result tree issues its own message using the message element. Each result tree also applies templates to a template matching function, though each in a different mode (text, xml, html, and xhtml). The different modes for each result help create an appropriate tree for each of the given formats. The new current-date( ) function is called in each result tree, too. To get this to work, you need to use a full Java version of Saxon, preferably Version 7.7 or later, available from http://saxon.sourceforge.net or in the examples/ch16 directory as saxon7-7.zip (the JAR file saxon7.jar has already been extracted from saxon7-7.zip). For specific instructions on how to download, install, and use Saxon with the Java interpreter, see the appendix. Once everything is installed and working, you can type this command: java -jar saxon7.jar functions.xml context.xsl and you will get the following text result tree, plus messages about the other three: Printing text result tree... Printing XML result tree in context.xml... Printing HTML result tree in context.html... Printing XHTML result tree in context-x.html... XPath 2.0 Context Functions Date: 2003-08-26 - fn:context-item( ) - fn:position( ) - fn:last( ) - fn:current-dateTime( ) - fn:current-date( ) - fn:current-time( ) - fn:default-collation( ) - fn:implicit-timezone( ) The files that the three result-document elements produced contain the other result trees. The first one is context.xml: <?xml version="1.0" encoding="UTF-8"?> <list> <description>XPath 2.0 Context Functions</description> <date>2003-10-03</date> <function>fn:context-item( )</function> <function>fn:position( )</function> <function>fn:last( )</function> <function>fn:current-dateTime( )</function> <function>fn:current-date( )</function> <function>fn:current-time( )</function> <function>fn:default-collation( )</function> <function>fn:implicit-timezone( )</function> </list> The second is context.html, an HTML document that uses an unordered (bulleted) list: <html> <body> <h2>XPath 2.0 Context Functions</h2> <h3>Date: 2003-10-03</h3> <ul> <li>fn:context-item( )</li> <li>fn:position( )</li> <li>fn:last( )</li> <li>fn:current-dateTime( )</li> <li>fn:current-date( )</li> <li>fn:current-time( )</li> <li>fn:default-collation( )</li> <li>fn:implicit-timezone( )</li> </ul> </body> </html> And the third is context-x.html, an XHTML document that uses an ordered (numbered) list: <html xmlns="http://www.w3.org/1999/xhtml"> <body> <h2>XPath 2.0 Context Functions</h2> <h3>Date: 2003-10-03</h3> <ol> <li>fn:context-item( )</li> <li>fn:position( )</li> <li>fn:last( )</li> <li>fn:current-dateTime( )</li> <li>fn:current-date( )</li> <li>fn:current-time( )</li> <li>fn:default-collation( )</li> <li>fn:implicit-timezone( )</li> </ol> </body> </html> As you can see, result-document provides a great convenience creating more than one result tree from just one stylesheet. Next is an example that uses regular expressions. |
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