how to add comment in the head of xml file

[Li Zongliang]

Hi all,

I write out XML file using DOM (and xalan ) from my java application, I want to add 
some comment text in the head of the output file. such as:

<?xml version="1.0" encoding="UTF-8"?>

<!-- this is the comment before the root element -->

<domain name="netguard">
  <server name="server1" host="lee"/>
  <server name="server2" home="panda">
    <service code="gxlu.Loger" name="Test"/>
  </server>
</domain> 

please tell me how to do.