Move your HTTP Handler to its own namespace.

• Create a file named src/example/routes.clj

  (ns example.routes)
             

• Cut and paste the handler function to that namespace.

  (ns example.routes)
  
  (defn handler
    [request]
    {:status 200
     :headers {"Content-Type" "text/html"}
     :body "Hello, world"})
               

• Make your example.main namespace refer to that function.

  Make sure to retain the #'.

  (ns example.main
    (:require [ring.adapter.jetty :as jetty]
              [example.routes :as routes]))
  
  (defn -main []
    (jetty/run-jetty #'routes/handler {:port 9999}))
               

• Test to make sure your server still works with just run

  Nothing behavior-wise should be different.