Using XSL Conditional Statements and Recursions

Using XSL Conditional Statements and Recursions
XSLT allows different approaches to recursion. With the use of xsl:template (match) and xsl:foreach, developers can perform recursive task.
XSL allows two elements for conditional processing, xsl:if and xsl:choose. With xsl:if a sequence
constructor is evaluated only if the specified condition in a test attribute returns true. However with
xsl:choose instruction supports selection of one choice when there are several possibilities.
xsl:template (match)
The xsl:template match uses the pattern defined in the match attribute to identify which nodes
apply the rule defined in the template. If more than one template rule meets the match criteria,
they are first considered in order of import precedence. The templates that have the highest import
precedence are applied to the resultant document. If there is still more than one template rule
that meets the match criteria and shares the same import precedence, they are next considered
in order of priority. The priority is either given by the value of the priority attribute, or is a default
priority that depends on the match pattern.
<xsl:template
name="name"
match="pattern"
priority=number>

</xsl:template>
Example

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xsl:stylesheet SYSTEM "http://commons.omniupdate.com/dtd/
standard.dtd">
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/
Transform" xmlns:ou="http://omniupdate.com/XSL/Variables">

<xsl:template match="/">

</xsl:template>
</xsl:stylesheet>
Attribute: name (optional): Specifies a name for the template. If this attribute is omitted, there must
be a match attribute.
Attribute: match (optional): Contains the match pattern for the template. If this attribute is omitted,
there must be a name attribute.
Attribute: priority (optional): A positive or negative integer or decimal number that denotes the
priority of the template.
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Using XSL Conditional Statements and Recursions
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Once a match pattern is successful, the rules defined in the template are applied to every node
satisfying the match pattern.
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Example

<root>
<faculty>
<first_name>John</first_name>
<last_name>Doe</last_name>
<department>Computer Science</department>
<phone>123-234-1234</phone>
</faculty>
<faculty>
<first_name>Peter</first_name>
<last_name>Parker</last_name>
<designation>Economics</designation>
<phone>234-123-7890</phone>
</faculty>
<faculty>
<first_name>Mary</first_name>
<last_name>Jane</last_name>
<designation></designation>
<phone></phone>
</faculty>
</root>
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xsl:stylesheet SYSTEM
"http://commons.omniupdate.com/dtd/
standard.dtd">
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/
Transform" xmlns:ou="http://omniupdate.com/XSL/Variables">

<xsl:template match="/">

</xsl:template>
</xsl:stylesheet>

<!DOCTYPE xsl:stylesheet SYSTEM "http://commons.omniupdate.com/dtd/
standard.dtd" >
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/
Transform">
<xsl:output method="html" indent="yes" encoding="UTF-8" omit-xmldeclaration="yes" />
<xsl:template match="/">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8"/>
<title>Faculty Table</title>
</head>
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Using XSL Conditional Statements and Recursions
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<table>
xsl:for-each
Recursion can also be accomplished using
xsl:for-each
. It allows developers to evaluate the sequence constructor within the
xsl:for-each
once for each item in that sequence. Using the same XML file as source, here is an example of
xsl:for-each
:
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Example
<!DOCTYPE xsl:stylesheet SYSTEM "http://commons.omniupdate.com/dtd/
standard.dtd" >
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/
Transform">
<xsl:output method="html" indent="yes" encoding="UTF-8" omit-xmldeclaration="yes" />
<xsl:template match="/">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8"/>
<title>Faculty Table</title>
</head>
<body>
<table>
<thead>
<tr>
<td>First Name</td>
<td>Last Name</td>
<td>Department</td>
<td>Phone Number</td>
</tr>
</thead>
<tbody>
<xsl:for-each select="/root/faculty">
<tr>
<td><xsl:value-of select="./first_name"/></td>
<td><xsl:value-of select="./last_name"/></td>
<td><xsl:value-of select="./department"/></td>
<td><xsl:value-of select="./phone"/></td>
</tr>
</xsl:for-each>
</tbody>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
xsl:if
xsl:if
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is used for conditional processing. It takes a mandatory
test
attribute, with a Boolean expression.
<xsl:if
test="expression">

</xsl:if>
Example

<xsl:variable name="raining" select="'yes'"/>
<xsl:if test="$raining='yes'"
>
Yes
</xsl:if>
Output
Yes
Attribute:
test
(mandatory): The Boolean condition to be tested.
xsl:when
xsl:when
is always used as a child element of
xsl:choose
. It defines a condition to be tested and, if the condition is true, the action to be performed.
<xsl:choose>
<xsl:when
test="expression">

</xsl:when>
<xsl:choose>
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Example

<xsl:variable name="raining" select="'yes'"/>
<xsl:choose>
<xsl:when test="$raining='yes'">
Yes
</xsl:when>
<xsl:when test="$raining='maybe'">
May be
</xsl:when>
</xsl:choose>
Output
Yes
Attribute:
test
(mandatory): The Boolean condition to be tested.
xsl:otherwise
xsl:otherwise
is always used as a child element of
xsl:choose
. It defines the action to be performed when none of the
xsl:when
conditions are satisfied.
<xsl:choose>
<xsl:when
test="expression">

</xsl:when>
<xsl:otherwise>

</xsl:otherwise>
<xsl:choose>
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Example

<xsl:variable name="raining" select="'yes'"/>
<xsl:choose>
<xsl:when test="$raining='yes'">
Yes
</xsl:when>
<xsl:when test="$raining='maybe'">
May be
</xsl:when>
<xsl:when test="$raining='no'">
No
</xsl:when>
<xsl:otherwise>
Don't know
</xsl:otherwise>
</xsl:choose>
Output
Yes
Attribute:
test
(mandatory): The Boolean condition to be tested.
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Using XSL Conditional Statements and Recursions
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