lecture 17. side remark: for-each equivalence again second-hand cars item model engine size price

Lecture 17

Side remark: for-each equivalence again

<?xml version="1.0"?>

<xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">

<html> <head><title>Second-hand cars</title></head> <body> <table rules="all">

<thead><tr><th>Item</th><th>Model</th><th>Engine Size</th><th>Price</th></tr></

thead> <tbody><xsl:apply-templates select="./stock/cars/item">

</tbody> </table></body></html></xsl:template>

<xsl:template match="item">

<xsl:variable name="thisType" select="./type"/>

<tr>

<td> <xsl:value-of select="./@num"/> </td>

<td> <xsl:value-of select="/stock/models/model[@id=$thisType]/name"/> </td>

<td> <xsl:value-of select="/stock/models/model[@id=$thisType]/engineSize"/> </td>

<td> <xsl:value-of select="./price"/> </td>

</tr>

</xsl:template>

</xsl:transform>

Conditional processing

• In essence, conditional processing is already provided by the select and match attributes

• However, XSLT also provides two construct for explicitly specifying conditional processing: the xsl:if element and xsl:choose element

• The xsl:if element

<xsl:if test = boolean-expression>  </xsl:if>

Example usage of the xsl:if element

<?xml version="1.0"?><xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:template match="/"><html> <head><title>Second-hand cars</title></head> <body> <table

rules="all"> <thead><tr><th>Item</th><th>Model</th><th>Engine Size</th><th>Price</th></tr></thead> <tbody><xsl:for-each select="./stock/cars/item"><xsl:variable name="thisType" select="./type"/><tr><td> <xsl:value-of select="./@num"/> </td><td> <xsl:value-of select="/stock/models/model[@id=$thisType]/name"/> </td><td> <xsl:value-of select="/stock/models/model[@id=$thisType]/engineSize"/> </td>

<td> <xsl:if test="price>=2500">Too expensive</xsl:if><xsl:if test="price < 2500"> <xsl:value-of select="price"/></xsl:if> </td></tr> </xsl:for-each> </tbody> </table></body></html></xsl:template></xsl:transform>

Conditional processing (contd.)

• Format of the xsl:choose element<xsl:choose>  </xsl:choose >

• Format of the xsl:when and xsl:otherwise elements

<xsl:when test = boolean-expression> </xsl:when >

<xsl:otherwise>  </xsl:otherwise>

Example usage of the xsl:choose element



<xsl:template match="/"><html> <head><title>Second-hand cars</title></head> <body> <table rules="all">

<thead><tr><th>Item</th><th>Model</th><th>Engine Size</th><th>Price</th></tr></thead> <tbody>

<xsl:for-each select="./stock/cars/item">


<tr><td> <xsl:value-of select="./@num"/> </td>


<td> <xsl:value-of select="/stock/models/model[@id=$thisType]/engineSize"/> </td> <td>

<xsl:choose>

<xsl:when test="price >= 2500">Too expensive</xsl:when>

<xsl:otherwise> <xsl:value-of select="price"/> </xsl:otherwise>

</xsl:choose></td></tr> </xsl:for-each>

</tbody> </table></body></html></xsl:template></xsl:transform>

Calling templates by name






<xsl:call-template name="show_item"/> </xsl:foreach></tbody> </table></body></html></xsl:template>

<xsl:template name="show_item">


<tr><td> <xsl:value-of select="./@num"/> </td>


<td> <xsl:value-of select="/stock/models/model[@id=$thisType]/engineSize"/> </td>

<td> <xsl:value-of select="./price"/> </td></tr>

</xsl:template></xsl:transform>

• Unlike xsl:apply-templates, xsl:call-template does not change the current node or the current node list

Passing parameter values to named templates






<xsl:variable name="thisVar" select="./type"/>

<xsl:call-template name="show_item">

<xsl:with-param name="thisNum" select="./@num"/>

<xsl:with-param name="thisName" select="/stock/models/model[@id=$thisVar]/name"/>

<xsl:with-param name="thisEngineSize" select="/stock/models/model[@id=$thisVar]/engineSize"/>

<xsl:with-param name="thisPrice" select="./price"/>

</xsl:call-template></xsl:for-each> </tbody> </table></body></html> </xsl:template>

<xsl:template name="show_item">

<xsl:param name="thisNum"/> <xsl:param name="thisName"/>

<xsl:param name="thisEngineSize"/> <xsl:param name="thisPrice"/>

<tr> <td> <xsl:value-of select="$thisNum"/> </td>

<td> <xsl:value-of select="$thisName"/> </td> <td> <xsl:value-of select="$thisEngineSize"/> </td>

<td> <xsl:value-of select="$thisPrice"/> </td> </tr> </xsl:template></xsl:transform>

A note on generating XML from PHP

The Usual situation in PHP

• By default, a PHP programmer does not have to generate headers for the HTTP responses that his programs generate– The PHP run-time system does this for him– It assumes that he is generating HTML

• Thus, the headers it generates include the following

Content-Type: text/html

Example PHP program

• The text that is generated look like XML

• But the header that will precede this text in the response message will be

Content-Type: text/html• Thus, the browser will treat the

response body as if it were a HTML file and will simply ignore the unrecognizable tags

Corrected PHP program

• The header that will precede this text in the response message will be

Content-Type: application/xml• The browser will treat the

response body as if it were an XML file

Server-side use of XSL stylesheets

Example PHP program

• The program below applies the stylesheet in carStyleSheet.xsl to the XML file in cars.xml and sends the resultant output to the browser which sent a HTTP request to the PHP program

<?php

$parser = xslt_create();

$html = xslt_process($parser, 'cars.xml','carStyleSheet.xsl');

xslt_free($parser);

echo $html;

?>

lecture 17. side remark: for-each equivalence again second-hand cars item model engine size price

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