import groovy.xml.NamespaceBuilder
import groovy.xml.MarkupBuilder

// create 'ivy.xml'
def ivyxml = new StringWriter()
def mkb = new MarkupBuilder(ivyxml)
mkb.doubleQuotes = true
mkb.'ivy-module' (version: '2.0') {
  info (organisation: 'apache', module: 'hello-ivy')
  dependencies {
    dependency (org: 'commons-lang', name: 'commons-lang', rev: '2.0')
    dependency (org: 'commons-cli' , name: 'commons-cli' , rev: '1.0')
  }
}
new File('./ivy.xml').text = ivyxml

// invoke ant
def ant = new AntBuilder()
def ivy = NamespaceBuilder.newInstance(ant, 'antlib:org.apache.ivy.ant')
ivy.retrieve()