Jan Stepien - Introducing structure in Clojure - Codemotion Milan 2017

Introducing structure with Jan Stępień @janstepien  janstepien.com

Functional  programming Operations, cont. delivery Generative testing Software architecture

Let’s talk about structure of web apps

Ports and adapters or Hexagonal  architecture or Clean architecture

Dependencies point only inwards

src └── table ├── entities │ └── booking.clj ├── use_cases │ └── book_table.clj └── adapters └── ring.clj

src └── table ├── entities │ └── booking.clj ├── use_cases │ └── book_table.clj └── adapters └── ring.clj Domain entities Use cases Adapters

(ns table.entities.booking (:require [clojure.spec.alpha :as spec])) (spec/def ::booking (spec/keys :req-un [::name ::seats ::time])) (spec/def ::name string?) (spec/def ::seats (spec/and integer? pos?)) (spec/def ::time #(instance? java.util.Date %))

(spec/explain ::booking {:name "" :seats 0 :time #inst “2017-06-06T21:00Z"})) (spec/valid? ::booking {:name "Stępień" :seats 3 :phone "+49876543210" :time #inst "2017-06-06T21:00Z"}))

(ns table.use-cases.book-table (:require [table.entities.booking :as booking] [clojure.spec.alpha :as spec])) (defn book-table [context booking] (save-booking (get context :save-booking) booking))

(ns table.use-cases.book-table (:require [table.entities.booking :as booking] [clojure.spec.alpha :as spec])) (defn book-table [context booking] (save-booking (get context :save-booking) booking)) (defprotocol SaveBooking (save-booking [this booking]))

(ns table.use-cases.book-table (:require [table.entities.booking :as booking] [clojure.spec.alpha :as spec])) (defn book-table [context booking] {:pre [(spec/valid? ::booking/booking booking)]} (save-booking (get context :save-booking) booking)) (defprotocol SaveBooking (save-booking [this booking]))

(let [booking {:name "Foo Bar" :seats 2 :time (java.util.Date.)} context {:save-booking (reify SaveBooking (save-booking [_ booking] (prn "Saved" booking)))}] (book-table context booking))

(ns table.adapters.ring (:require [table.use-cases.book-table :as book-table])) (defn post-booking [context req] (let [booking (coerce-params (get req :params))] (book-table/book-table context booking) "Success!")) (defn list-bookings [context req] ...)

(ns table.adapters.ring (:require [compojure.core :as compojure :refer [GET POST]] [ring.middleware.params :as params])) (defn routes [context] (compojure/routes (GET "/bookings" [] (fn [req] (list-bookings context req))) (POST "/bookings" [] (fn [req] (post-booking context req))))) (defn handler [context] (params/wrap-params (routes context)))

src └── table ├── entities │ └── booking.clj ├── use_cases │ └── book_table.clj └── adapters └── ring.clj Something is clearly missing

src └── table ├── entities │ └── booking.clj ├── use_cases │ └── book_table.clj ├── adapters │ └── ring.clj ├── system.clj └── system ├── postgres.clj └── http_server.clj

(ns table.system.postgres (:require [com.stuartsierra.component :as component])) (defrecord Postgres [config connection] component/Lifecycle (start [this] (assoc this :connection (connect config))) (stop [this] (close connection) (assoc this :connection nil)))

(ns table.system.postgres (:require [table.use-cases.book-table :as book-table])) (extend-protocol book-table/SaveBooking Postgres (save-booking [postgres booking] (execute-sql "insert into bookings..." booking))) (defn postgres [config] (map->Postgres {:config config}))

(ns table.system.http-server (:require [com.stuartsierra.component :as component])) (defrecord HttpServer [handler context server] component/Lifecycle (start [this] (assoc this :server (start-server (handler context)))) (stop [this] (stop-server server) (assoc this :server nil))) (defn http-server [handler] (map->HttpServer {:handler handler}))

(ns table.system (:require [com.stuartsierra.component :as component] [table.system [http-server :as http] [postgres :as postgres]] [table.adapters.ring :as ring])) (defn system [config] (component/system-map :postgres (postgres/postgres config) :context (component/using {} {:save-booking :postgres}) :http (component/using (http/http-server ring/handler) {:context :context})))

src └── table ├── entities │ └── booking.clj ├── use_cases │ └── book_table.clj ├── adapters │ └── ring.clj ├── system.clj ├── system │ ├── postgres.clj │ └── http_server.clj └── main.clj

(ns table.main (:require [com.stuartsierra.component :as component] [table.system :as system])) (defn -main [] (let [config {:postgres {:host "localhost" :user "foo" :password "bar"}}] (component/start (system/system config))))

clojure.spec for contracts Compojure and ring-core for HTTP Component and System for lifecycle Luminus or Duct for a framework

Jan Stepien - Introducing structure in Clojure - Codemotion Milan 2017

More Related Content

What's hot

Similar to Jan Stepien - Introducing structure in Clojure - Codemotion Milan 2017

More from Codemotion

Recently uploaded

Jan Stepien - Introducing structure in Clojure - Codemotion Milan 2017