How to Generate an XSLT Transform Using Groovy StreamingMarkupBuilder

BY ALEX TATIYANTS

October 3rd, 2012

Groovy and XSLT are two great options for working with XML. While both have their uses, I was curious about combining them to generate an XSLT transform with a Groovy script. It turns out that doing this is pretty straight forward, with a couple of minor caveats.

Namespaces

XSLT commands like template and value-of are defined in the “http://www.w3.org/1999/XSL/Transform” namespace (commonly aliased with xsl). Therefore, generating XML with XSLT commands requires using a namespace.

Luckily, Groovy’s StreamingMarkupBuilder has support for namespaces via a special markup object called mkp, which contains declareNamespace() function:

def xmlWithNamespace = new StreamingMarkupBuilder().bind {
mkp.declareNamespace(abc: "some namespace")
}

Once declared, creating an node using the namespace is simply a matter of using the “.” notation: 

namespace.nodeName {
namespace.anotherNodeName {
...
}
}

Unfriendly Casing Style

Like most other W3C standards, XSLT uses “lower-case-with-hyphens” casing style for its keywords: value-of, apply-templates, and so on. This creates a slight complication for Groovy because words with hyphens are not valid symbols (i.e. xsl.value-of{} won’t work). Instead, you have to surround these terms in quotes: xsl."value-of"{}.

Final Result

So, here’s a Groovy script to generate a simple XSLT transform:

def xmlWithNamespace = new StreamingMarkupBuilder().bind {
mkp.declareNamespace(mynamespace: "http://www.w3.org/1999/XSL/Transform")
}
xsl.stylesheet(version:"2.0") {
xsl.template(match:"/") {
html {
head {
title("list of items")
}
}
body {
h1("items") {
ul {
xsl."apply-templates"(select:"items/item")
}
}
}
}
xsl.template(match:"item") {
li {
xsl."value-of"(select:"name")
}
}
}
}

And here’s the XSLT the script above generates:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:template match="/">
<html>
<head>
<title>list of items</title>
</head>
</html>
<body>
<h1>
<ul>
<xsl:apply-templates select="items/item"/>
</ul>
</h1>
</body>
</xsl:template>
<xsl:template match="item">
<li>
<xsl:value-of select="name"/>
</li>
</xsl:template>
</xsl:stylesheet>

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This post got 3 comments so far. Care to add yours?

  1. Evgenia says:
    February 7, 2013 at 3:10 pm

    thanks a lot, Alex. I was exactly looking for this code snippet!

  2. Adeel says:
    August 5, 2014 at 2:56 pm

    I am facing this error.

    Error : can not resolve symbol ‘xsl’