Missing *out* in Clojure with Lein and Ring - clojure

Question

I am running Lein 2 and cider 0.7.0. I made a sample ring app that uses ring/run-jetty to start.
(ns nimbus-admin.handler
(:require [compojure.core :refer :all]
[compojure.handler :as handler]
[clojure.tools.nrepl.server :as nrepl-server]
[cider.nrepl :refer (cider-nrepl-handler)]
[ring.adapter.jetty :as ring]
[clojure.tools.trace :refer [trace]]
[ring.util.response :refer [resource-response response redirect content-type]]
[compojure.route :as route])
(:gen-class))
(defroutes app-routes
(GET "/blah" req "blah")
(route/resources "/")
(route/not-found (trace "not-found" "Not Found")))
(def app (handler/site app-routes))
(defn start-nrepl-server []
(nrepl-server/start-server :port 7888 :handler cider-nrepl-handler))
(defn start-jetty [ip port]
(ring/run-jetty app {:port port :ip ip}))
(defn -main
([] (-main 8080 "0.0.0.0"))
([port ip & args]
(let [port (Integer. port)]
(start-nrepl-server)
(start-jetty ip port))))
then connect to it with cider like:
cider-connect 127.0.0.1 7888
I can navigate to my site and eval forms in emacs and it will update what is running live in my nrepl session, so that is great.
I cannot see output, either with (print "test") (println "test") (trace "out" 1)
Finally, my project file:
(defproject nimbus-admin "0.1.0"
:description ""
:url ""
:min-lein-version "2.0.0"
:dependencies [[org.clojure/clojure "1.6.0"]
[com.climate/clj-newrelic "0.1.1"]
[com.ashafa/clutch "0.4.0-RC1"]
[ring "1.3.1"]
[clj-time "0.8.0"]
[midje "1.6.3"]
[org.clojure/tools.nrepl "0.2.6"]
[ring/ring-json "0.3.1"]
[org.clojure/tools.trace "0.7.8"]
[compojure "1.1.9"]
[org.clojure/data.json "0.2.5"]
[org.clojure/core.async "0.1.346.0-17112a-alpha"]
]
:plugins [[lein-environ "1.0.0"]
[cider/cider-nrepl "0.7.0"]]
:main nimbus-admin.handler)
I start the site with lein run
Edit
I CAN see output, ONLY when using (.println System/out msg)

Answer 1

Have you tried (.println System/out msg)? I had the same problem and this worked for me.

Answer 2

It's possible to just put print statements in your code manually.
If you want to print information about each request, you can add middleware.
The handler you pass to jetty is a function from Ring requests to Ring responses.
Ring request and responses are just maps, see the Ring spec for more which keys they should contain.
Middleware is just a function that takes a handler as its first argument and returns a handler.
Example of a middleware function to print basic info about requests and responses:
(defn log-middleware [handler]
(fn [request]
(let [response (handler request)]
(println "=>" (name (:request-method request)) ":" (:uri request))
(println "<=" (:status request))
response)))
This middleware should print to the cider repl buffer, but cider behaves strangely
sometimes and send output to *Messages* or the nrepl server buffer.
You use this middleware by applying it to your handlers:
(def application (log-middleware (handler/site routes)))
Headers could be printed this way to: just get the :headers field form the request map and print it.

Answer 3

The Prone library may help you out. It is has a ring middleware for better exception reporting that also has the ability for debugging. When debugging, you can inspect any local bindings as well as the Ring request.
Here is a video that demonstrates how it works

Answer 4

Use (flush) after your print expressions to force output.