This document provides an overview of testing, accessing relational data, and building web applications in Clojure. It discusses using the test-is and test namespaces for testing, clojure.contrib.sql for database access using JDBC, and Compojure for building web apps with routing and HTML generation. Examples are given for writing tests, performing CRUD operations on a database, and building a web app frontend to view and create snippets.

1. Clojure in the Wild

2. Contents
Unit Test
Acessing Relational data
Web app

3. Test with :test

4. Test with :test
examples/index_of_any.clj
(test #'index-of-any)
⇒ :ok
(defn
#^{:test (fn []
(assert (nil? (busted))))}
busted [] "busted")
(test #'busted)
⇒ java.lang.Exception: Assert failed: (nil? (busted))

5. Test with test-is
Write test with this!!
(clojure.contrib.test-is/deftest testname & forms)
Use 'is' Macro instead of assertions.
(clojure.contrib.test-is/is form message?)
Ready to run all tests?
(clojure.contrib.test-is/run-tests & namespaces)

6. Test with test-is
(deftest test-that-demonstrates-failure
(is (= 5 (+ 2 2))))
(run-tests)
Testing user
FAIL in (test-that-demonstrates-failure) (NO_SOURCE_FILE:5)
expected: (= 5 (+ 2 2))
actual: (not= 5 4)
Ran 1 tests containing 1 assertions.
1 failures, 0 errors.

7. Test with test-is
Exception handling with (is (thrown? ))
(deftest test-divide-by-zero
(is (thrown? ArithmeticException (/ 5 0))))
(run-tests)
Testing examples.test
Ran 1 tests containing 1 assertions.
0 failures, 0 errors.
{:type :summary, :test 1, :pass 1, :fail 0, :error 0}

8. Other Options for Test
All Clojure sequences implement Java collection interfaces.
All Clojure functions implement Callable and Runnable.
So, you can write your tests with any Java-compatible test
framework:
JUnit, TestNG, or even EasyB or JTestR.
Good luck!

9. Data Access
clojure.contrib.sql -> thin wrappers for JDBC
The entry point for sql is the with-connection macro:
(clojure.contrib.sql/with-connection db-spec & body)
(use 'clojure.contrib.sql)
; START: db
; replace "snippet-db" with a full path!
(def db {:classname "org.hsqldb.jdbcDriver"
:subprotocol "hsqldb"
:subname "file:snippet-db"})
; END: db
; db-spec -> JDBC's DriverManager

10. Data Access
Create Table by create-table function
(clojure.contrib.sql/create-table name & column-specs)
(use 'clojure.contrib.sql)
(defn create-snippets []
(create-table :snippets
[:id :int "IDENTITY" "PRIMARY KEY" ]
[:body :varchar "NOT NULL" ]
[:created_at :datetime]))
(with-connection db (create-snippets))
(0)
(with-connection db (create-snippets)))
java.lang.Exception: transaction rolled back: failed batch

11. Data Access
Insert-values functions for adds rows
(clojure.contrib.sql/insert-values table column-names & values)
(defn now [] (java.sql.Timestamp. (.getTime (java.util.Date.))))
(defn insert-snippets []
(let [timestamp (now)]
(seq
(insert-values :snippets
[:body :created_at]
["(println :boo)" timestamp]
["(defn foo [] 1)" timestamp]))))
(with-connection db (insert-snippets)))
(1 1)

12. Data Access
issues some sql and then executes
the forms in body with results
->
with-query-results
(with-query-results results sql & body)
(defn print-snippets []
(with-query-results res ["select * from snippets" ]
(println res)))
(with-connection db (print-snippets))
({:id 0, :body (println :boo),
:created_at #<Timestamp 2009-01-03 11:40:19.985>}
{:id 1, :body (defn foo [] 1),
:created_at #<Timestamp 2009-01-03 11:40:19.985>})

13. Data Access
; Broken!
(defn select-snippets []
(with-query-results res ["select * from snippets" ] res))
(with-connection db (select-snippets)))
java.sql.SQLException: No data is available
JDBC results can be lazy & select-snippets return lazy seqs
(defn sql-query [q]
(with-query-results res q (doall res)))
(with-connection db (sql-query ["select body from snippets"]))

14. Data Access
transaction macro
(clojure.contrib.sql/transaction & body)
; ID of the new snippet
(defn last-created-id [] (first (vals (first (sql-query ["CALL IDENTITY()" ])))))
(defn insert-snippet [body]
(with-connection db
(transaction
(insert-values :snippets
[:body :created_at]
[body (now)])
(last-created-id))))
(insert-snippet "(+ 1 1)")
) 4
(insert-snippet "(ref true)")
) 5

15. Other library Options
Higher level tool options
-> use a java framework(Hibernate,iBatis,ActiveRecord..)
-> use a clojure-specific persistence libraries(clj-
record,clojureql)
clj-record example
(ns clj-record.test.model.manufacturer
(:require [clj-record.core :as cljrec])
(cljrec/init-model
(has-many products)
(validates name "empty!" #(not (empty? %)))
(validates name "starts with whitespace!" #(not (re-find #"^s" %)))
(validates name "ends with whitespace!" #(not (re-find #"s$" %)))
(validates grade "negative!" #(or (nil? %) (>= % 0))))
clojureql example
(execute (sql
(query [id name] developers.employees (and (> id 5) (< id 8)))))

16. Web DevelopmentCompojure & Jetty web server
simple routes create by defroutes
(compojure/defroutes name doc & routes)
routes (HTTP-VERB url-pattern body)
run-server
(compojure/run-server options? & paths-and-servlets)
(use 'compojure)
(defroutes snippet-app
"Create and view snippets."
(GET "/ping" "pong" )
(ANY "*"
(page-not-found)))
(run-server {:port 8080}
"/*" (servlet snippet-app))

17. Building HTML
test-area function
(compojure/text-area options? name value?)
html function to actual html
(compojure/html & trees)
(use 'compojure) (text-area "body"))
[:textarea {:id "body", :name "body"} nil]
(println (html (text-area "body")))
<textarea id="body" name="body"></textarea>

18. Building HTML
(compojure/form-to handler & body)
(compojure/submit-button options? & text)
(defn new-snippet []
(html
(form-to [:post "/" ]
(text-area {:rows 20 :cols 73} "body" )
[:br]
(submit-button "Save" ))))
(println (new-snippet))
| <form action="/" method="POST">
| <textarea cols="73" id="body" name="body" rows="20"></textarea>
| <br />
| <input type="submit" value="Save" />
| </form>

19. Posts and Redirects
redirect
(compojure/redirect-to location)
(defn create-snippet [body]
(if-let [id (insert-snippet body)]
(redirect-to (str "/" id))
(redirect-to "/" )))

20. Finishing Touches
(compojure/serve-file root? path)
(GET "/public/*" (or (serve-file (params :*)) :next))
(compojure/include-js & scripts)
(compojure/include-css & scripts)
(defn layout [title & body]
(html
[:head
[:title title]
(include-js "/public/javascripts/code-highlighter.js"
"/public/javascripts/clojure.js" )
(include-css "/public/stylesheets/code-highlighter.css" )]
[:body
[:h2 title]
body]))

21. Finishing Touches
(defn show-snippet [id]
(layout (str "Snippet " id)
(let [snippet (select-snippet id)]
(html
[:div [:pre [:code.clojure (:body snippet)]]]
[:div (:created_at snippet)]))))