Clojure-Web-Applikationen für Beginner

Clojure ist eine JVM-Sprache, die das Unmögliche möglich macht: Ein tatsächlich in der Praxis von normalsterblichen Entwicklern einsetzbares Lisp.

Neben den Grundlagen von Clojure werden Sie in dieser Session auch lernen wie man hiermit Web-Anwendungen umsetzten kann. Wenn Sie sich hierbei nicht von den Lisp-typischen Klammern abschrecken lassen werden Sie schnell sehen, dass der Einsatz einer rein funktionalen Programmiersprache sehr gut zum statuslosen Ansatz von HTTP passt.

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1. Clojure-Web-Applikationen für Beginner BOB 2016
2. Michael Vitz michael.vitz@innoq.com Consultant @ innoQ @michaelvitz
3. http://upload.wikimedia.org/wikipedia/en/1/
4. Clojure > Lisp-Variante auf JVM > Funktionale Sprache > Dynamisch typisiert > komplettes mächtiges Macrosystem
5. Datenstrukturen “Hello World" 3 3.14 3/2 \a :first foo #“Ch.*se” (“Hello”, :first) [3 4 3] { :name “Michael”, :company “innoQ” } #{3 4 3}
6. Syntax “You’ve just seen it” - Rich Hickey
7. Funktionen (+ 1 2) > 3 (:city {:name “innoQ” :city “Monheim”}) > “Monheim” (map inc [1 2 3]) > (2 3 4)
8. Funktionen (fn [x y] (+ x y)) (def add (fn [x y] (+ x y))) (defn add
 [x y] (+ x y))
9. 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
10. Web-Applikationen
11. Web-Applikation App Request Response
12. Web-Applikation App(Request) = Response
13. Web-Applikation (defn greet-controller
 [request] {:status 200
 :headers {“Content-Type” “text/plain”} :body “Hello, world!”})
14. Ring https://github.com/ring-clojure/ring
15. Ring Request Response Ring App
16. Ring: Handler (defn greet-controller
 [request] {:status 200
 :headers {“Content-Type” “text/plain”} :body “Hello, world!”})
17. Ring: Middleware (defn wrap-logging
 [handler] (fn [request] (print request)
 (let [response (handler request)] (print response) response)))
18. Ring: Middleware > https://github.com/ring-clojure/ring-defaults > https://github.com/ring-clojure/ring-json
19. Ring: Adapter > Jetty > Servlet > http-kit > Tomcat > …
20. Ring: Request {:uri “/greet”
 :query-string “name=Michael” :request-method :get :headers { … } …}
21. Ring: Response {:status 200 :headers { … }
 :body “Hello, Michael!”}
22. Ring HTTP Request HTTP Response Adapter Middleware 1 Middleware 2 Middleware n Handler Request Response
23. Compojure https://github.com/weavejester/compojure
24. Compojure Request Response Ring Compojure App
25. Compojure: Handler (def handler (GET “/hello” [] “Hello, world!”)) (handler {:request-method :get, :uri “/hello”}) > {:body “Hello, world!”} (handler {:request-method :post, :uri “/hello”}) > nil
26. Exkurs: Macros
27. Clojure: Macros “(case 3 1 “one” 2 “two” “more”)” Reader Text Data Structures (case 3 1 “one” 2 “two” “more”)
28. Clojure: Macros Evaluator Data Structures (case 3 1 “one” 2 “two” “more”) Data Structures (if (= 3 1) “one” (if (= 3 2) “two” “more”))
29. Zurück zu Compojure…
30. Compojure: Macro (GET “/hello” [] “Hello, world!”) (fn [req] (if (and (= (:uri req) “/hello”) (= (:request-method req) :get)) {:body “Hello, world!”}))
31. Compojure: Path (GET “/hello/:name” [name] (str “Hello, ” name “!”))
32. Compojure: Routes (def my-routes (routes (GET “/hello” [] “Hello!”) (GET “/bye” [] “Bye!”))) (defroutes my-routes (GET “/hello” [] “Hello!”) (GET “/bye” [] “Bye!”))
33. Compojure: Alternativen > https://github.com/juxt/bidi > http://clojure-liberator.github.io/liberator/
34. Hiccup https://github.com/weavejester/hiccup
35. Hiccup Request Response Ring Compojure App Hiccup
36. Hiccup: Basics [:div {:id “foo”} [:span “bar”]] <div id=“foo”> <span>bar</span> </div>
37. Hiccup: Shortcuts [:div#foo [:span “bar”]] <div id=“foo”> <span>bar</span> </div>
38. Hiccup: Links (link-to “www.innoq.com” “innoQ”) <a href=“www.innoq.com”> innoQ </a> [:a {:href “www.innoq.com”} “innoQ”]
39. Hiccup: Formulare (form-to [:post “/login”] (text-field “Username”) (password-field “Password”) (submit-button “Login”))
40. Hiccup: Alternativen > https://github.com/danlarkin/clabango > https://github.com/plakat/clj-thymeleaf > https://github.com/cgrand/enlive > https://github.com/yogthos/Selmer
41. Fazit
42. Fazit > Funktionale Sprache ideal für Web-App > Verbreitung nimmt zu > Libraries anstelle von Frameworks > Community gesund und hilfsbereit
43. Interessante 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
44. Frameworks > https://github.com/weavejester/duct > http://www.luminusweb.net > https://github.com/otto-de/tesla-microservice > https://github.com/metosin/compojure-api
45. Danke! Fragen?
    Kommentare? Michael Vitz | @michaelvitz michael.vitz@innoq.com innoQ Deutschland GmbH Krischerstr. 100 40789 Monheim am Rhein Germany Phone: +49 2173 3366-0 www.innoq.com Ohlauer Straße 43 10999 Berlin Germany Ludwigstraße 180 E D-63067 Offenbach Germany Kreuzstr. 16 D-80331 München Germany https://www.innoq.com/en/talks/2016/02/clojure-webapps/