Clojure Web-Application 101

Clojure is a JVM language which makes the impossible come true: a pragmatic and usable Lisp for humans. Besides an short introduction to the language this talk introduces how to develop Web-Applications in Clojure. If you aren't afraid of parenthesis you will quickly understand why a functional language like Clojure is a perfect choice for implementing Web-Applications and that it fits the stateless HTTP approach very nicely.

Transcript

1. @michaelvitz #Devoxx #Clojure Clojure Web-Application 101 Michael Vitz innoQ
2. @michaelvitz #Devoxx #Clojure http://upload.wikimedia.org/wikipe
3. @michaelvitz #Devoxx #Clojure Clojure • Lisp on the JVM • Functional • Dynamically typed • Immutable data structures • macros
4. @michaelvitz #Devoxx #Clojure Data structures “Hello World" 3 3.14 3/2 \a :first foo #“Ch.*se” (“Hello” :first) [3 4 3] { :name “Michael”, :company “innoQ” } #{3 4 3} true nil false
5. @michaelvitz #Devoxx #Clojure Syntax “You’ve just seen it” - Rich Hickey
6. @michaelvitz #Devoxx #Clojure Functions (+ 1 2) > 3 (:city {:name “Devoxx” :city “Antwerp”}) > “Antwerp” (map inc [1 2 3]) > (2 3 4)
7. @michaelvitz #Devoxx #Clojure Functions (fn [x y] (+ x y)) (def add (fn [x y] (+ x y))) (defn add
 [x y] (+ x y))
8. @michaelvitz #Devoxx #Clojure Links • http://clojure.org • blog.cognitect.com/blog/2016/1/28/state-of-clojure-2015- survey-results • https://juxt.pro/radar.html • http://www.clojure-toolbox.com
9. @michaelvitz #Devoxx #Clojure Web-Applications
10. @michaelvitz #Devoxx #Clojure Web-Application fn request response
11. @michaelvitz #Devoxx #Clojure Web-Application (defn greet-controller
 [request] {:status 200
 :headers {“Content-Type” “text/plain”} :body “Hello, world!”})
12. @michaelvitz #Devoxx #Clojure Ring https://github.com/ring-clojure/ring
13. @michaelvitz #Devoxx #Clojure Ring webapp Java HTTP Server Ring Server Adapter
14. @michaelvitz #Devoxx #Clojure Ring: Request {:uri “/greet”
 :query-string “name=Michael” :request-method :get :headers { … } …}
15. @michaelvitz #Devoxx #Clojure Ring: Response {:status 200 :headers { … }
 :body “Hello, Michael!”}
16. @michaelvitz #Devoxx #Clojure Ring: Handler (defn greet-controller
 [request] {:status 200
 :headers {“Content-Type” “text/plain”} :body “Hello, world!”})
17. @michaelvitz #Devoxx #Clojure Ring: Adapter • Jetty • Servlet • http-kit • Tomcat • …
18. @michaelvitz #Devoxx #Clojure Ring: Middleware (defn wrap-logging
 [handler] (fn [request] (print request)
 (let [response (handler request)] (print response) response)))
19. @michaelvitz #Devoxx #Clojure Ring: Middleware • https://github.com/ring-clojure/ring-defaults • https://github.com/ring-clojure/ring-json
20. @michaelvitz #Devoxx #Clojure Ring webapp Java HTTP Server Ring Server Adapter middleware middleware
21. @michaelvitz #Devoxx #Clojure Compojure https://github.com/weavejester/compojure
22. @michaelvitz #Devoxx #Clojure Compojure routing fn route 1 route 2 route 3 not-found request response
23. @michaelvitz #Devoxx #Clojure Compojure: Handler (def handler (GET “/hello” [] “Hello, world!”)) (handler {:request-method :get, :uri “/hello”}) > {:body “Hello, world!”} (handler {:request-method :post, :uri “/hello”}) > nil
24. @michaelvitz #Devoxx #Clojure Excursion: Macros
25. @michaelvitz #Devoxx #Clojure Compojure: Macro “(case 3 1 “one” 2 “two” “more”)” Reader Text Data Structures (case 3 1 “one” 2 “two” “more”)
26. @michaelvitz #Devoxx #Clojure Data Structures Compojure: Macro Evaluator (case 3 1 “one” 2 “two” “more”) Data Structures (if (= 3 1) “one” (if (= 3 2) “two” “more”))
27. @michaelvitz #Devoxx #Clojure Back to Compojure…
28. @michaelvitz #Devoxx #Clojure Compojure: Macro (GET “/hello” [] “Hello, world!”) (fn [req] (if (and (= (:uri req) “/hello”) (= (:request-method req) :get)) {:body “Hello, world!”}))
29. @michaelvitz #Devoxx #Clojure Compojure: Path (GET “/hello/:name” [name] (str “Hello, ” name “!”))
30. @michaelvitz #Devoxx #Clojure Compojure: Routes (def my-routes (routes (GET “/hello” [] “Hello!”) (GET “/bye” [] “Bye!”))) (defroutes my-routes (GET “/hello” [] “Hello!”) (GET “/bye” [] “Bye!”))
31. @michaelvitz #Devoxx #Clojure Compojure
32. @michaelvitz #Devoxx #Clojure Compojure: Alternatives • https://github.com/juxt/bidi • http://clojure-liberator.github.io/liberator/
33. @michaelvitz #Devoxx #Clojure Hiccup https://github.com/weavejester/hiccup
34. @michaelvitz #Devoxx #Clojure Hiccup: Basics [:div {:id “foo”} [:span “bar”]] <div id=“foo”> <span>bar</span> </div>
35. @michaelvitz #Devoxx #Clojure Hiccup: Shortcuts [:div#foo [:span “bar”]] <div id=“foo”> <span>bar</span> </div>
36. @michaelvitz #Devoxx #Clojure Hiccup: Links (link-to “www.innoq.com” “innoQ”) <a href=“www.innoq.com”> innoQ </a> [:a {:href “www.innoq.com”} “innoQ”]
37. @michaelvitz #Devoxx #Clojure Hiccup: Forms (form-to [:post “/login”] (text-field “Username”) (password-field “Password”) (submit-button “Login”))
38. @michaelvitz #Devoxx #Clojure Hiccup: Alternatives • https://github.com/danlarkin/clabango • https://github.com/plakat/clj-thymeleaf • https://github.com/cgrand/enlive • https://github.com/yogthos/Selmer
39. @michaelvitz #Devoxx #Clojure Wrap-Up
40. @michaelvitz #Devoxx #Clojure Wrap-Up • Functional language fits to HTTP cycle • Clojure usage increases • Libraries vs. Frameworks • Healthy and welcome community
41. @michaelvitz #Devoxx #Clojure Interesting libraries • https://github.com/technomancy/leiningen • https://github.com/weavejester/environ • https://github.com/clojurewerkz/route-one • https://github.com/krisajenkins/yesql • https://github.com/seancorfield/clj-time
42. @michaelvitz #Devoxx #Clojure “Frameworks” • https://github.com/weavejester/duct • http://www.luminusweb.net • https://github.com/otto-de/tesla-microservice • https://github.com/metosin/compojure-api