如何使用Parser实例将XML写入文件？

This is my Groovy code:

这是我的Groovy代码：

// ...
def xml = new XmlParser().parse(fileName)
xml.each { e ->
  // some changes are being made to XML
  xml.append("test", "test me")
}
def writer = new FileWriter(newFileName)
new XmlNodePrinter(new PrintWriter(writer)).print(xml)
// ..