How to dynamically render XML in Grails?

I'm setting up an application that initiates phone calls based on XML files specific to each call instance. For testing purposes, I was using the Groovy MarkupBuilder and StringWriter methods to write my XMLs to a single file, and then overwrite that file the next time a call was initiated.

However, this will not work in production, because we will be overwriting XML that is currently in use. So, I'd like to dynamically create XML in a controller by calling it with something like:

callInstance.createXml()

with the "createXml" method containing the rules for how to render the XML specifically for each call.

I've found multiple instances of people asking how to turn an object into a dynamically created XML file, but this is a little different since I'm having to use the MarkupBuilder.

For a quick reference, here's small example of what I'm working with:

def f1 = new File('filename')
f1.delete()
def writer = new StringWriter()
        def xml = new MarkupBuilder(writer)
            xml.doubleQuotes = true
            xml.vxml(version开发者_开发百科:'2.1'){
                property(name:"termchar", value:"#")
                var(name:"hi", expr:"'Hello!'")
                xml.form(){
                    block(){
                        value(expr:"hi")
                        xml.goto(next:"#next") //etc, etc
                    }
                }
            }
        //break
        f1.createNewFile()
            f1 << writer.toString()

Thanks in advance!

One thing you could do (in your controller) is to send the XML back from the render method like so:

def callxml = {
  def call = Call.get( params.id )
  render( contentType:"text/xml" ) {
    vxml( version:'2.1' ) {
      var( name:'hi', expr:call.message )
    }
  }
}

Or, you could add a method to the Call class, so it knows how to convert itself to XML as a String:

class Call {
  String message

  String toXml() {
    def writer = new StringWriter()
    new groovy.xml.MarkupBuilder( writer ).with { xml ->
      xml.doubleQuotes = true
      vxml(version:'2.1'){
        var(name:"hi", expr:"${this.message}")
      }
    }
    writer.toString()
  }
}

Then you should be able to call call.toXml()