Template engine for use in templating scenarios where both the template source and the expected output are intended to be XML.

Templates may use the normal '${expression}' and '$variable' notations to insert an arbitrary expression into the template. In addition, support is also provided for special tags: <gsp:scriptlet> (for inserting code fragments) and <gsp:expression> (for code fragments which produce output).

Comments and processing instructions will be removed as part of processing and special XML characters such as <, >, " and ' will be escaped using the respective XML notation. The output will also be indented using standard XML pretty printing.

The xmlns namespace definition for gsp: tags will be removed but other namespace definitions will be preserved (but may change to an equivalent position within the XML tree).

Normally, the template source will be in a file but here is a simple example providing the XML template as a string:

def binding = [firstname:"Jochen", lastname:"Theodorou",
               nickname:"blackdrag", salutation:"Dear"]
def engine = new groovy.text.XmlTemplateEngine()
def text = '''\
<?xml version="1.0" encoding="UTF-8"?>
<document xmlns:gsp='http://groovy.codehaus.org/2005/gsp' xmlns:foo='baz' type='letter'>
  <gsp:scriptlet>def greeting = "${salutation}est"</gsp:scriptlet>
  <gsp:expression>greeting</gsp:expression>
  <foo:to>$firstname "$nickname" $lastname</foo:to>
  How are you today?
</document>
'''
def template = engine.createTemplate(text).make(binding)
println template.toString()

This example will produce this output:

<document type='letter'>
Dearest
<foo:to xmlns:foo='baz'>
  Jochen &quot;blackdrag&quot; Theodorou
</foo:to>
How are you today?
</document>

The XML template engine can also be used as the engine for groovy.servlet.TemplateServlet by placing the following in your web.xml file (plus a corresponding servlet-mapping element):

<servlet>
  <servlet-name>XmlTemplate</servlet-name>
  <servlet-class>groovy.servlet.TemplateServlet</servlet-class>
  <init-param>
    <param-name>template.engine</param-name>
    <param-value>groovy.text.XmlTemplateEngine</param-value>
  </init-param>
</servlet>

new XmlTemplateEngine(configurePrinter: { it.preserveWhitespace = true })