One Ring to Bind Them

Notes de l'éditeur

1. thanks stu
2. so, ring
3. ring is a tool for writing http services in clojure
4. put another way ring helps you write web apps in clojure
8. not go through mechanics, why it’s best to udnerstand not as a list of features but as a line of reasoning
9. how that power leads to better apps
10. how that power leads to better apps
11. how that power leads to better apps
12. so let’s start at the beginning this is an http request to your clojure web service what you would like to do is take this http request,
13. apply your clojure application logic
14. and generate an http response, like this one seems easy enough
15. it’s just http to clojure and back but if you try working with raw http in your app, or with an http-specific api like, say, servlets,
16. you are going to be sad the reason is that the http protocol is not the essence of your particular app that essence is more like
17. this
18. the fact that http looks like this on the socket coming in
19. or like this going out are not details you want to concern your application code with
20. abstraction
21. so what then is the abstraction?
22. well, we said our app was essentially this which looks suspiciously like a function
23. there, that’s better now the request is really more than /welcome
24. we really need to include various named fields, like the protocol, request method, uri, and host. key-value pairs: sounds like a map to me
25. so ring represents http requests as vanilla clojure maps
26. likewise http responses are logically a set of key-value pairs
27. so we again use clojure maps to represent http responses in ring
28. so the upshot of is that our web application looks like this the http application is a function that function takes a map as an argument, representing the http request that function then returns a map, representing the http response this is simple to the point of being obvious, but it’s really important
29. the reason is that we’ve lifted http into the space of clojure’s maps and functions these are universal interfaces that clojure the language, clojure programs, and clojure libraries all understand
30. the reason is that we’ve lifted http into the space of clojure’s maps and functions these are universal interfaces that clojure the language, clojure programs, and clojure libraries all understand
31. the reason is that we’ve lifted http into the space of clojure’s maps and functions these are universal interfaces that clojure the language, clojure programs, and clojure libraries all understand
32. defining middleware
33. defining middleware
34. defining middleware
36. composing middleware
37. likewise you don’t need any ring-specific gear to test your applications - they are just functions on data. Indeed the look exactly any other Clojure function, so why not unit test them the same way you unit test all of your other Clojure code.
38. all of that clojure’s general functional programming awesomeness transitively applies to web app development, for free so abstraction, and in particular choosing the right abstraction which is nice
39. but i promised you this right we’ll get that last bit by taking our power and applying
40. leverage
41. leverage
42. it says what those maps needs to look like and what that function needs to do
43. the spec is short and mostly obvious, but its critical because it allows all kinds of libraries to easily participate in your application
44. ring itself is part library
45. ring itself is part library
46. it includes some basic web building blocks out of box these are some examples but these are really just for convenience of distribution anyone can write a ring component that works with that spec
47. batteries inclued, hello world and basic funtionality that you would expect of a web applicaiton library
48. response example
49. session store as example of providing common interface
50. and it can immediately participate in the ring ecosystem instead of a bunch of project on github like rails-my-extensions we have a bunch like ring-my-extension, that can then be shared easily among all
51. we’re seeing a lot of great stuff built around Ring
52. a couple areas that i’d like to highlight are frameworks, adapters, and middleware
55. ~ can run and augment orthogonally
56. then in part because it doesn’t need to touch http at all, and part because it leverages other ring-based libraries, compojure itself is really small so if you ever have a problem with compojure, or just want to know how it works, you could just read the entire source in a few minutes
63. so what you end up with is you have base app that defines our core routing and business logic and then you take some middleware from ring core, pull in some middleware from the ring ecosystem, and tyically also have a few of your own middleware that are specific for this project what middleware config looks like in one of my apps so
64. so the ring abstraction leads to power, which in turn allows you to write better http apps in clojure what i’d like to do now is
65. generalize this slightly into some thoughts about library design in clojure
66. the key for ring’s design was taking http, and transforming it into the space of clojure’s pervasive abstractions
67. in a well-specified way that enabled composability
68. in particular composability that extended across orthogonal components that were written independently, but again all leveraging clojure’s core strengths
69. composability across developers and through clojure’s extensive functional programming library this is what i call
70. composable abstraction
71. to me, personally, this notion of composable abstraction is the essence of clojure
72. i see all of clojure’s bullet-point features i think ring is an instance of this - i hope i’ve convinced you of that - but it’s also a sort of archetype for clojure library design
73. this notion worked well with ring, but where could it be useful elsewhere
74. we actually don’t even need to leave http to see a great example you could apply the same trick here
77. because then, again, you immediately benefit from the power of clojure everything is functions and data, and clojure is brilliant with those
78. so looking back on our original list for ring i’d say that ring is the direct result of a library design approach that can - and i think should - be applied to more problems
79. in other words, if you want steps 2 and 3 here
80. you have to the step one right, abstraction
81. thanks for listening everyone i’d love to take some questions
82. thanks again