I am learning Clojure for the web. I am trying to implement Bidi and Ring in Lein app. When I open the site I get a 500 error:
HTTP ERROR: 500
Problem accessing /. Reason:
Response map is nil
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My files are the following:
./project.clj
(defproject bidi-ring "0.1.0-SNAPSHOT"
:description "FIXME: write description"
:url "http://example.com/FIXME"
:license {:name "EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0"
:url "https://www.eclipse.org/legal/epl-2.0/"}
:dependencies [[org.clojure/clojure "1.10.0"]
[bidi "2.1.6"]
[ring/ring-core "1.6.3"]
[ring/ring-jetty-adapter "1.6.3"]]
:repl-options {:init-ns my.app}
:main my.app)
./src/my/handler.clj
(ns my.handler (:gen-class)
(:require [bidi.ring :refer (make-handler)]
[ring.util.response :as res]))
(defn index-handler
[request]
(res/response "Homepage"))
(defn article-handler
[{:keys [route-params]}]
(res/response (str "You are viewing article: " (:id route-params))))
(def handler
(make-handler ["/" {"index.html" index-handler
["articles/" :id "/article.html"] article-handler}]))
./src/my/app.clj
(ns my.app (:gen-class)
(:require [my.handler :refer [handler]]
[ring.middleware.session :refer [wrap-session]]
[ring.middleware.flash :refer [wrap-flash]]))
(use 'ring.adapter.jetty)
(defn -main []
(def app
(-> handler
wrap-session
wrap-flash))
(run-jetty app {:port 3000}))
How to fix it?
You have made a mistake in your routes. Look at this Bidi demo repo:
https://github.com/io-tupelo-demo/bidi
The code on line 16 of tst.demo.core
shows what is happening. In bidi
, a route "/index.html" does not include the degenerate route "/":
(let [routes ["/" ; common prefix
{"index.html" :index
"article.html" :article}]
routes-2 ["/" ; common prefix
{"" :index ; add a default route so "/" and "/index.html" both => `:index` handler
"index.html" :index
"article.html" :article}]]
(is= (bidi/match-route routes "/index.html") {:handler :index}) ; normal case
(is= (bidi/match-route routes "/") nil) ; plain "/" route is not available, has no default
(is= (bidi/match-route routes-2 "/") {:handler :index})) ; Now we get the :index route
When no route matches, match-route
returns a nil
, which the server then translates into a 500 not-found
that is sent to the browser.