Render gsp template from file, delegating to script

render_gsp_template.groovy

import org.springframework.core.io.ByteArrayResource

def s = new File('/Users/ben/Documents/foo/index.gsp').withReader { reader ->
  return reader.text
}
def resource = new ByteArrayResource(s.bytes)

def renderer = ctx.groovyPagesTemplateEngine
def template = renderer.createTemplate(resource, false)

def output = new StringWriter()
template.make([s: this]).writeTo(output) // s is accessible in template: s.buildActionUrl('bar')

private String buildActionUrl(name) {
  return "http://foo.com/$name"
}