Ring provides a common abstraction for building web applications in Clojure. It defines handlers as functions that take HTTP requests as maps and return responses as maps. Adapters run handlers on web servers, and middleware can augment handlers. This allows writing web apps in an idiomatic way and sharing code across frameworks that target the Ring spec.

1. Ring
Web Apps in Idiomatic Clojure
Mark McGranaghan
January 23, 2010

2. About Mark
Bowdoin College ’10
Clojure user since 2008
Open source: http://github.com/mmcgrana

3. Motivation for Ring

4. Motivation for Ring
Abstract HTTP

5. Motivation for Ring
Abstract HTTP
Write apps in idiomatic Clojure

6. Motivation for Ring
Abstract HTTP
Write apps in idiomatic Clojure
Share code across web frameworks

7. Motivation for Ring
Abstract HTTP
Write apps in idiomatic Clojure
Share code across web frameworks
Deploy on a variety of web servers

8. Motivation for Ring
Abstract HTTP
Write apps in idiomatic Clojure
Share code across web frameworks
Deploy on a variety of web servers
WSGI & Rack

9. The Ring Project

10. The Ring Project
Spec

11. The Ring Project
Spec
Library

12. The Ring Project
Spec
Library
Ecosystem

13. Overview of Ring

14. Overview of Ring
Handlers are functions

15. Overview of Ring
Handlers are functions
that take requests as Clojure maps

16. Overview of Ring
Handlers are functions
that take requests as Clojure maps
and return responses as Clojure map

17. Overview of Ring
Handlers are functions
that take requests as Clojure maps
and return responses as Clojure map
Adapters run handlers on a web server

18. Overview of Ring
Handlers are functions
that take requests as Clojure maps
and return responses as Clojure map
Adapters run handlers on a web server
Middleware augments handlers

19. “Ring”

20. Request Map
{:uri <String>
:query-string <String>
:request-method <Keyword>
:headers <IPersistentMap>
:body <InputStream>
... ...}

21. Response Map
{:status <Integer>
:headers <IPersistentMap>
:body <String, ISeq, File, InputStream>}

22. Example: Hello World
(defn app [req]
{:status 200
:headers {"Content-Type" "text/html"}
:body (str "Hi from " (:server-name req))})

23. Example: Hello World
(defn app [req]
{:status 200
:headers {"Content-Type" "text/html"}
:body (str "Hi from " (:server-name req))})
(use ’ring.adapter.jetty)
(run-jetty app {:port 8080})

24. Example: Hello World

25. Example: Stacktraces
(defn app [req]
("o noes"))

26. Example: Stacktraces
(defn app [req]
("o noes"))
(use ’ring.adapter.jetty)
(use ’ring.middleware.stacktrace)
(run-jetty (wrap-stacktrace app) {:port 8080})

27. Example: Stacktraces

28. Example: Static Files
(defn dynamic-app [req]
(...))

29. Example: Static Files
(defn dynamic-app [req]
(...))
(use ’ring.middleware.file)
(use ’ring.middleware.file-info)
(def app
(-> dynamic-app
(wrap-file "public")
(wrap-file-info)))

30. Example: Testability

31. Example: Testability
(defn my-app [req]
(...))

32. Example: Testability
(defn my-app [req]
(...))
(deftest not-found-error
(let [req {:uri "/bogus/uri"}
resp (my-app req)]
(is (= 404 (:status resp)))))

33. Ring and Web Frameworks

34. Ring and Web Frameworks
Foundation, not replacement

35. Ring and Web Frameworks
Foundation, not replacement
Avoid duplication and share code

36. Ring and Web Frameworks
Foundation, not replacement
Avoid duplication and share code
Compojure, Conjure, Weld all targeting Ring

37. Ring and Web Frameworks
Foundation, not replacement
Avoid duplication and share code
Compojure, Conjure, Weld all targeting Ring
Compojure case study

38. Ring Middleware

39. Ring Middleware
ring.middleware.reload: Automatically
reload namespaces

40. Ring Middleware
ring.middleware.reload: Automatically
reload namespaces
ring.middleware.params: Get request
params as a map

41. Ring Middleware
ring.middleware.reload: Automatically
reload namespaces
ring.middleware.params: Get request
params as a map
ring.middleware.cookies: Cookie jar
abstraction

42. Other Components

43. Other Components
ring.util.servlet: If you really want a
Servlet

44. Other Components
ring.util.servlet: If you really want a
Servlet
ring.adapter.httpcore: Adapter for HTTP
Core library

45. Other Components
ring.util.servlet: If you really want a
Servlet
ring.adapter.httpcore: Adapter for HTTP
Core library
ring.handler.dump: See the request map

46. Other Components
ring.util.servlet: If you really want a
Servlet
ring.adapter.httpcore: Adapter for HTTP
Core library
ring.handler.dump: See the request map
ring.examples.*: Runnable examples

47. Future Work

48. Future Work
Middleware and utility extraction from
frameworks

49. Future Work
Middleware and utility extraction from
frameworks
Not a framework itself

50. Future Work
Middleware and utility extraction from
frameworks
Not a framework itself
More use in production?

51. Future Work
Middleware and utility extraction from
frameworks
Not a framework itself
More use in production?
User needs?

52. Learn More
http://github.com/mmcgrana/ring
ring/example/*.clj
ring/SPEC