Functional Web Architecture

Designing web applications with Ring and Compojure

Transcript

1. Functional Web Architecture Designing web applications with Ring and Compojure twitter: @weavejester code: github.com/weavejester
2. Ring. What is it?
3. An abstraction over HTTP
4. What's HTTP?
5. A request / response protocol
6. HTTP Request Server Response
7. Ring user=> (server request) response
8. Ring user=> (handler request) response
9. HTTP Request GET /resource HTTP/1.1 Host: www.example.com
10. HTTP Request GET /resource HTTP/1.1 Host: www.example.com method URI headers
11. Request Map {:request-method :get :uri "/resource" :headers {"host" "www.example.com"}}
12. HTTP Response HTTP/1.1 200 OK Content-Type: text/plain Hello World
13. HTTP Response HTTP/1.1 200 OK Content-Type: text/plain Hello World status body headers
14. Response Map {:status 200 :headers {"Content-Type" "text/plain"} :body "Hello World"}
15. Ring Map Function Map
16. No other abstractions
17. HTTP Request Server Response Ring Map Function Map
18. HTTP Request Server Response Ring Map Function Map Adapter
19. Example (defn handler [request] {:status 200 :headers {"Content-Type" "text/plain"} :body "Hello World"})
20. Example (use 'ring.util.response) (defn handler [request] (-> (response "Hello World") (content-type "text/plain")))
21. Example (use 'ring.util.response 'ring.adapter.jetty) (defn handler [request] (-> (response "Hello World") (content-type "text/plain"))) (run-jetty handler {:port 3000})
22. Why abstract at all?
23. Power
24. Power to leverage Clojure
25. Middleware
26. Not a new abstraction Just higher order functions
27. Handler Middleware Handler Map Handler Map
28. Handler Request Response
29. Middleware Handler Request Response
30. Middleware Handler Request Response
31. Identity (defn wrap-identity [handler] (fn [request] (handler request)))
32. Caching (defn wrap-cache [handler] (fn [request] (or (get-cache request) (let [response (handler request)] (put-cache! request response) response))))
33. Content Types (defn wrap-content-type [handler] (fn [request] (let [ext (get-ext (:uri request)) type (ext-types ext)] (-> (handler request) (content-type type)))))
34. Parameters (defn wrap-params [handler] (fn [request] (let [query (:query-string request) params (parse-params query)] (handler (assoc request :params params)))))
35. Ring core middleware • Query and form parameters • Multipart file uploads • Cookies • Sessions • Content-types • Static resources
36. Routing Multiple resources from the same handler
37. Basic Routing (use 'ring.util.response) (defn handler [request] (case (:uri request) "/hello" (response "Hello") "/world" (response "World") :else (not-found "Page not found")))
38. Compojure
39. Compojure (use 'compojure.core) (def hello-route (GET "/hello" request "hello"))
40. Compojure ; (GET "/hello" request "hello") (def hello-route (fn [request] (if (and (= (:request-method request) :get) (= (:uri request) "/hello")) "hello" nil))))
41. Compojure ; (GET "/hello" request "hello") (def hello-route (fn [request] (if (and (= (:request-method request) :get) (= (:uri request) "/hello")) "hello" nil))))
42. Compojure ; (GET "/hello" request "hello") (def hello-route (fn [request] (if (and (= (:request-method request) :get) (= (:uri request) "/hello")) "hello" nil))))
43. Compojure ; (GET "/hello" request "hello") (def hello-route (fn [request] (if (and (= (:request-method request) :get) (= (:uri request) "/hello")) "hello" nil))))
44. Compojure ; (GET "/hello" request "hello") (def hello-route (fn [request] (if (and (= (:request-method request) :get) (= (:uri request) "/hello")) "hello" nil))))
45. Compojure (use 'compojure.core) (def handler (routes (GET "/hello" _ "hello") (GET "/world" _ "world")))
46. Compojure (use 'compojure.core) (defroutes handler (GET "/hello" _ "hello") (GET "/world" _ "world"))
47. GET /hello GET /world Routes Request Response
48. GET /hello GET /world Routes nil Request Response
49. GET /hello GET /world Routes nil Request nil
50. Compojure (use 'compojure.core) (require '[compojure.route :as route]) (defroutes handler (GET "/hello" _ "hello") (GET "/world" _ "world") (route/not-found "Page Not Found"))
51. GET /hello route/not-found GET /world Routes nil Request Response nil
52. Compojure (use 'compojure.core) (require '[compojure.route :as route]) (defroutes handler (GET "/hello" _ "hello") (GET "/world" _ "world") (route/not-found "Page Not Found"))
53. Compojure (use 'compojure.core) (require '[compojure.route :as route]) (defroutes handler (GET "/:word" request (-> request :params :word)) (route/not-found "Page Not Found"))
54. Compojure (use 'compojure.core) (require '[compojure.route :as route]) (defroutes handler (GET "/:word" {{word :word} :params} word) (route/not-found "Page Not Found"))
55. Compojure (use 'compojure.core) (require '[compojure.route :as route]) (defroutes handler (GET "/:word" [word] word) (route/not-found "Page Not Found"))
56. Compojure (use 'compojure.core) (require '[compojure.route :as route] '[clojure.string :as str]) (defroutes handler (GET "/:word" [word] word) (GET "/:word/shout" [word] (str/upper-case word)) (route/not-found "Page Not Found"))
57. Compojure (use 'compojure.core) (require '[compojure.route :as route] '[clojure.string :as str]) (defroutes handler (context "/:word" [word] (GET "/" word) (GET "/shout" (str/upper-case word))) (route/not-found "Page Not Found"))
58. Compojure • Create handlers (GET, POST...) • Cascade handlers (routes) • Nest handlers (context)
59. Compojure (wrap-authorize (context "/user/:uid" [uid] (let [user (get-user uid)] (routes (GET "/" [] @user) (PUT "/" [& data] (put! user data)) (DELETE "/" [] (delete! user))))))
60. Compojure (defn rest-routes [model] (routes (GET "/" [] @model) (PUT "/" [& data] (put! model data)) (DELETE "/" [] (delete! user))) (wrap-authorize (context "/user/:uid" [uid] (rest-routes (get-user uid))
61. What's the big idea?
62. Complex handlers can be a composition of smaller handlers
63. Function Orientated Architecture
64. What next? Content negotiation Finite State Machines REST abstractions Clojurescript integration
65. Fin. Questions?