Return contents of a file in a route

[Mark]

I want to be able to simulate a system that I'm integrating with.  I'd like
a route to return the contents of a file in a REST DSL route.  Is it
possible to do this in Camel?  This is what I'd like to do:

restConfiguration()
   .component("jetty")
   .host("localhost")
   .port(1234)
   .bindingMode(RestBindingMode.off);

  rest().path("/mystuff")
       .get("/testing").bindingMode(RestBindingMode.json)
  .route()
.setHeader(Exchange.CONTENT_TYPE).constant("application/json")

         <!-- set body to contents of file -->
          ???  .from("file:myfile.json");   ???

I tried adding the "from("file:myfile.json")" to my route, but the results
do not come back.