Recipe14.1.Saxon Extension Functions

Recipe 14.1. Saxon Extension Functions

XSLT 1.0 (Saxon Version 6.5.4)

Saxon lets you access extension functions written in Java by using the interface defined in the XSLT 1.1 draft standard.

Java is the only extension language currently supported by Saxon, so extension function bindings are defined along the lines of the following example:

<xsl:stylesheet   version="1.1"   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"  xmlns:Math="java:java.lang.Math"   exclude-result-prefixes="Math">     <xsl:script implements-prefix="Math"                    xmlns:Math="java:java.lang.Math"                    language="java"                    src="/books/2/765/1/html/2/java:java.lang.Math"/>

Here the naming convention used for the namespace is not strictly required. However, if followed, it makes the xsl:script element optional. Hence, if you need to access an extension only once, you can write something like:

<xsl:stylesheet   xmlns:xsl="http://www.w3.org/1999/XSL/Transform">      <xsl:variable name="PI" select="4 * Math:atan(1.0)"                 xmlns:Math="java:java.lang.Math"/> <!-- ... --> </xsl:stylesheet>

Here the namespace encodes the binding to the Java implementation rather than the xsl:script. Note that these binding techniques are independent; if you use the xsl:script element, then the namespace's content does not matter. On the other hand, if you omit the xsl:script, the namespace has the sole responsibility of binding the Java implementation.

XSLT 2.0 (Saxon Version 8.x)

The mechanism for invoking Java-based extension functions is largely the same as Saxon 6.5.4. However, the saxon:script element is deprecated and may be withdrawn in a future release according to the product's web site. The preferred method is to declare a top-level namespace of the form java: followed by the fully-qualified class name.

<xsl:stylesheet version="2.0"   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"   xmlns:math="java:java.lang.Math"   exclude-result-prefixes="math">   <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>      <xsl:template match="/">     <pi><xsl:value-of select="4 * math:atan(1.0)"/></pi>   </xsl:template>    </xsl:stylesheet>