Custom Functions using Saxon HE

INTRODUCTION

• Saxon is a powerful XSLT and XQuery Processor.
• Saxon has 3 versions.
• 1) HE-Home Edition,
• 2) PE-Professional Edition and
• 3) EE-Enterprise Edition.
• Saxon-HE version is an open source. Libraries can be downloaded from https://sourceforge.net/projects/saxon/files/Saxon-HE/ or online maven repository https://mvnrepository.com/artifact/net.sf.saxon/Saxon-HE/
• Saxon-PE & EE versions are licensed.

SOFTWARES & TOOLS

1. Eclipse IDE (Mars) with Maven Plugin
2. Java 8
3. Saxon-HE-9.7.0-18

EXAMPLE

Saxon has many inbuilt functions but after 9.2 version, those functions are moved to licensed versions PE & HE. We need to have proper license file to use the inbuilt functions.

In this post, we are going to learn how to write custom functions using Saxon-HE. These custom functions also called integrated extension functions.

Follow the below steps to calculate & display age using the date of birth of the employees.

Step 1

Create a Maven Project in eclipse and copy paste the below code into pom.xml dependency.

<dependency>      <groupId>net.sf.saxon</groupId>      <artifactId>Saxon-HE</artifactId>      <version>9.7.0-18</version> </dependency>

Step 2

Create a Java Class AgeCalculator.java which extends ExtensionFunctionDefinition.java as below.

package jbr.saxon; import java.time.LocalDate; import java.time.Period; import net.sf.saxon.expr.XPathContext; import net.sf.saxon.lib.ExtensionFunctionCall; import net.sf.saxon.lib.ExtensionFunctionDefinition; import net.sf.saxon.om.Sequence; import net.sf.saxon.om.StructuredQName; import net.sf.saxon.trans.XPathException; import net.sf.saxon.value.SequenceType; import net.sf.saxon.value.StringValue; public class AgeCalculator extends ExtensionFunctionDefinition { @Override public SequenceType[] getArgumentTypes() { return new SequenceType[] { SequenceType.SINGLE_STRING }; } @Override public StructuredQName getFunctionQName() { return new StructuredQName("emp", "http://example.com/saxon-extension", "ageCalc"); } @Override public SequenceType getResultType(SequenceType[] arg0) { return SequenceType.SINGLE_STRING; } @Override public ExtensionFunctionCall makeCallExpression() { return new ExtensionFunctionCall() { @Override public Sequence call(XPathContext ctx, Sequence[] args) throws XPathException { String output = null; String[] input = args[0].iterate().next().getStringValue().split("-"); int year = Integer.valueOf(input[0]); int month = Integer.valueOf(input[1]); int dayOfMonth = Integer.valueOf(input[2]); LocalDate dob = LocalDate.of(year, month, dayOfMonth); output = String.valueOf(Period.between(dob, LocalDate.now()).getYears()); return StringValue.makeStringValue(output); } }; } }

Note:

1. Mention no. of arguments and its types at getArgumentTypes() method
2. Define the output type at getResultType() method
3. I have written inner class in makeCallExpression() method for my simple requirement, you can create separate class and extend ExtensionFunctionCall.java
4. http://example.com/saxon-extension - you can give any url.
5. Also, you can choose your own name for emp & ageCalc

Step 3

Create a Java class AgeCalculatorMain.java to test the custom function as below.

package jbr.saxon; import java.io.File; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.stream.StreamResult; import javax.xml.transform.stream.StreamSource; import net.sf.saxon.Configuration; import net.sf.saxon.TransformerFactoryImpl; import net.sf.saxon.trans.XPathException; public class AgeCalculatorMain { public static void main(String[] args) throws XPathException { // Set saxon as your transformer. System.setProperty("javax.xml.transform.TransformerFactory", "net.sf.saxon.TransformerFactoryImpl"); // specify input and output transform("testdata/input/employees.xml", "testdata/input/employees.xsl", "testdata/output/output.html"); } public static void transform(String sourcePath, String xsltPath, String resultDir) { try { TransformerFactory factory = TransformerFactory.newInstance(); if (factory instanceof TransformerFactoryImpl) { TransformerFactoryImpl tFactoryImpl = (TransformerFactoryImpl) factory; Configuration config = tFactoryImpl.getConfiguration(); config.registerExtensionFunction(new AgeCalculator()); } Transformer transformer = factory.newTransformer(new StreamSource(new File(xsltPath))); transformer.transform(new StreamSource(new File(sourcePath)), new StreamResult(new File(resultDir))); System.out.println("Output generated successfully at: " + resultDir); } catch (TransformerException e) { e.printStackTrace(); } } }

Step 4

Create an input xml file (employees.xml)

<?xml version="1.0" encoding="UTF-8"?> <employees>  <employee>    <name>Anbu</name>    <address>Chennai</address>    <dob>1990-05-15</dob>    <phone>9600096000</phone>    <email>anbu@email.com</email>  </employee>  <employee>    <name>Bala</name>    <address>Hydrabad</address>    <dob>1989-01-04</dob>    <phone>9700097000</phone>    <email>bala@email.com</email>  </employee>  <employee>    <name>Chandru</name>    <address>Mumbai</address>    <dob>1995-11-10</dob>    <phone>9900099000</phone>    <email>chandru@email.com</email>  </employee> </employees>

Step 5

Create an XSLT file (employees.xsl). Define the custom function and call it.

<?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:emp="http://example.com/saxon-extension">  <xsl:template match="/">    <html>      <body>        <h2>Employee Details</h2>        <table border="1">          <tr bgcolor="#9acd32">            <th style="text-align:left">Name</th>            <th style="text-align:left">Address</th>            <th style="text-align:left">Date of Birth</th>            <th style="text-align:left">Age</th>            <th style="text-align:left">Phone</th>            <th style="text-align:left">Email</th>          </tr>          <xsl:for-each select="employees/employee">            <tr>              <td>                <xsl:value-of select="name" />              </td>              <td>                <xsl:value-of select="address" />              </td>              <td>                <xsl:value-of select="dob" />              </td>              <td>                <xsl:value-of select="emp:ageCalc(dob)" />              </td>              <td>                <xsl:value-of select="phone" />              </td>              <td>                <xsl:value-of select="email" />              </td>            </tr>          </xsl:for-each>        </table>      </body>    </html>  </xsl:template> </xsl:stylesheet>

OUTPUT

Now Run the AgeCalculatorMain.java and the output html file will be copied to /testdata/output/output.html

Open the output.html in any browser.

Complete Source Code

That’s all about writing a custom function using Saxon HE version. Please share your comments.

Happy Knowledge Sharing!!!