Examples for Clojure Ring (#6881)

clojure/ring/.gitignore

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+/target
+/classes
+/checkouts
+profiles.clj
+pom.xml
+pom.xml.asc
+*.jar
+*.class
+/.lein-*
+/.nrepl-port
+.hgignore
+.hg/

clojure/ring/README.md

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+# Clojure Ring Examples
+
+This project acts as a set of examples for the Clojure Ring library.
+
+## Runing the examples
+
+The examples can all be run from the Leiningen REPL.
+
+Firstly, start the REPL with `lein repl`. Then the examples can be executed with:
+
+* `(run simple-handler)` - A simple handler that just echos a constant string to the client
+* `(run check-ip-handler)` - A handler that echos the clients IP Address back to them
+* `(run echo-handler)` - A handler that echos the value of the "input" parameter back
+* `(run request-count-handler)` - A handler with a session that tracks how many times this session has requested this handler
+
+In all cases, the handlers can be accessed on http://localhost:3000.

clojure/ring/project.clj

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+(defproject baeldung-ring "0.1.0-SNAPSHOT"
+  :dependencies [[org.clojure/clojure "1.10.0"]
+                 [ring/ring-core "1.7.1"]
+                 [ring/ring-jetty-adapter "1.7.1"]
+                 [ring/ring-devel "1.7.1"]]
+  :plugins [[lein-ring "0.12.5"]]
+  :ring {:handler ring.core/simple-handler}
+  :repl-options {:init-ns ring.core})

clojure/ring/src/ring/core.clj

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+(ns ring.core
+  (:use ring.adapter.jetty
+        [ring.middleware.content-type]
+        [ring.middleware.cookies]
+        [ring.middleware.params]
+        [ring.middleware.session]
+        [ring.middleware.session.cookie]
+        [ring.util.response]))
+
+;; Handler that just echos back the string "Hello World"
+(defn simple-handler [request]
+  {:status 200
+   :headers {"Content-Type" "text/plain"}
+   :body "Hello World"})
+
+;; Handler that echos back the clients IP Address
+;; This demonstrates building responses properly, and extracting values from the request
+(defn check-ip-handler [request]
+    (content-type
+        (response (:remote-addr request))
+        "text/plain"))
+
+;; Handler that echos back the incoming parameter "input"
+;; This demonstrates middleware chaining and accessing parameters
+(def echo-handler
+  (-> (fn [{params :params}]
+        (content-type
+          (response (get params "input"))
+          "text/plain"))
+      (wrap-params {:encoding "UTF-8"})
+  ))
+
+;; Handler that keeps track of how many times each session has accessed the service
+;; This demonstrates cookies and sessions
+(def request-count-handler
+  (-> (fn [{session :session}]
+        (let [count (:count session 0)
+              session (assoc session :count (inc count))]
+          (-> (response (str "You accessed this page " count " times."))
+              (assoc :session session))))
+      wrap-cookies
+      (wrap-session {:cookie-attrs {:max-age 3600}})
+  ))
+
+;; Run the provided handler on port 3000
+(defn run
+  [h]
+  (run-jetty h {:port 3000}))