I have a controller method, that return an XML format. How do I convert it to Mono. Example:

 Mono<String> response = 
  <?xml version = "1.0" encoding = "utf-8"?>
    <plane>
       <year> 1977 </year>
       <make> Cessna </make>
       <model> Skyhawk </model>
       <color> Light blue and white </color>
    </plane>

how do I convert this response to Mono.