RESTEasy supports Range requests for java.io.File response entities.

   @Path("/")
   public class Resource {
      @GET
      @Path("file")
      @Produces("text/plain")
      public File getFile()
      {
         return file;
      }
   }

      Response response = client.target(generateURL("/file")).request()
              .header("Range", "1-4").get();
      Assert.assertEquals(response.getStatus(), 206);
      Assert.assertEquals(4, response.getLength());
      System.out.println("Content-Range: " + response.getHeaderString("Content-Range"));