Thursday, January 1, 2009

Clojure http-client.clj

I've been playing with Clojure recently. I've been following along in the Beta version of Programming Clojure, which uses r1097 of clojure for all examples. Being too much of a newbie, I did not want to stray.

The problem that I ran into was that the http-client.clj posted to the clojure group would not compile. As best I can tell, it seems that the clojure.core namespace used to be simply clojure. Search and replace quickly solved that.

The syntax for doseq also looks to have been updated -- square brackets are required, so:
        (doseq kw (keys (http-defaults :set-header))
(. conn (setRequestProperty kw (get (http-defaults :set-header) kw))))

        (doseq [kw (keys (http-defaults :set-header))]
(. conn (setRequestProperty kw (get (http-defaults :set-header) kw))))

My working version:
;;  Copyright (c) Dirk Vleugels. All rights reserved.
;; The use and distribution terms for this software are covered by the
;; Common Public License 1.0 (
;; which can be found in the file CPL.TXT at the root of this distribution.
;; By using this software in any fashion, you are agreeing to be bound by
;; the terms of this license.
;; You must not remove this notice, or any other, from this software.
;; http-client.clj 0.1
;; Usage:
;; (http-client/url-do "" "GET" { :read-timeout 5000
;; :set-header { "User-Agent" "Clojure-HttpClient/0.1
;; "X-Header-xxx" "This is a test" }
;; :connect-timeout 1000
;; :http-proxy ""
;; :follow-redirect false
;; :use-caches false } ))
;; (http-client/url-do "" "POST" {:read-timeout 5000
;; :connect-timeout 1000
;; :use-caches false }
;; "this is a post test"))
;; Returns a map or (currently) throws a exception
;; {:return-message "Found", :return-code 302, :header {nil [HTTP/1.1 302 Found], "Server" [GFE/1.3], "Content-Type" [text/html; charset=UTF-8], "Date" [Thu, 10 Jul 2008 19:31:52 GMT], "Location" [], "Content-Length" [218]}, :body [B@bed1e7}
;; A clojure interface for the jdk http client (requires jdk 1.5)
;; - ignores SSL cert or host verification problems (thats what i want 99% of the time)
;; Todo:
;; - exception handling + resource cleanup, logging?
;; dirk.vleugels (gmail)
;; 8 Juli 2008

;;(load-file "/Users/dvl/work/clojure/svn/clojure/trunk/src/genclass.clj")
(clojure.core/in-ns 'http-client)
(clojure.core/refer 'clojure.core)

(import '( URL URLConnection InetSocketAddress Proxy Proxy$Type)
'( Reader InputStream InputStreamReader FileReader
BufferedReader File PrintWriter OutputStream ByteArrayOutputStream
OutputStreamWriter BufferedWriter Writer FileWriter)
'( X509TrustManager HostnameVerifier SSLContext HttpsURLConnection)
'( X509Certificate))

(def http-defaults {:read-timeout 10000
:connect-timeout 3000
:http-proxy ""
:set-header { "User-Agent" "Clojure-HttpClient/0.1" }
:use-caches false
:follow-redirects false})

;; provide dummy trust manager
(let [ clazz "httpclient.CljTrustManager" ]
(try (. Class (forName (str clazz)))
(catch java.lang.ClassNotFoundException e
(gen-and-load-class (str clazz) :implements []))))
(clojure.core/in-ns 'httpclient.CljTrustManager)
(clojure.core/refer 'clojure.core)
(defn checkClientTrusted [this chain auth-type])
(defn checkServerTrusted [this chain auth-type])
(defn getAcceptedIssuers [this ] nil)
(clojure.core/in-ns 'http-client)
;; end

;; provide hostname verifier
(let [ clazz "httpclient.CljHostnameVerifier" ]
(try (. Class (forName (str clazz)))
(catch java.lang.ClassNotFoundException e
(gen-and-load-class (str clazz) :implements []))))
(clojure.core/in-ns 'httpclient.CljHostnameVerifier)
(clojure.core/refer 'clojure.core)
(defn verify [this hostname ssl-session] true)
(clojure.core/in-ns 'http-client)
;; end

(defn- create-proxy [proxy]
(if (= proxy "")
(. Proxy NO_PROXY)
(let [u (new URL proxy)
host (. u getHost)
port (if (neg? (. u getPort)) 8080 (. u getPort))
sa (new InetSocketAddress host port)
prx (new Proxy (. Proxy$Type HTTP) sa)]

(defn url-do [url method defaults & body]
"Connect to given url, execute given HTTP method. defauls may be empty {}, body is only
used for POST requests"
(binding [ http-defaults (merge http-defaults defaults) ]
(let [p (create-proxy (http-defaults :http-proxy))
u (new URL url)]
(when (. (. url toLowerCase) startsWith "https")
(let [sc (. SSLContext getInstance "SSLv3")
tma (new httpclient.CljTrustManager)
ar (make-array httpclient.CljTrustManager 1)]
(aset ar 0 tma)
(. sc (init nil ar nil))
(. HttpsURLConnection setDefaultSSLSocketFactory (. sc getSocketFactory))
(. HttpsURLConnection setDefaultHostnameVerifier (new httpclient.CljHostnameVerifier))))

(let [ conn (. u openConnection p) ]
(doto conn
(setRequestMethod method)
(setUseCaches (http-defaults :use-caches))
(setReadTimeout (http-defaults :read-timeout))
(setInstanceFollowRedirects (http-defaults :follow-redirects))
(setConnectTimeout (http-defaults :connect-timeout)))
(doseq [kw (keys (http-defaults :set-header))]
(. conn (setRequestProperty kw (get (http-defaults :set-header) kw))))
(when (= method "POST")
(when (nil? body) (throw (new Exception "need body for post request")))
(. conn setDoOutput true)
(doto (new OutputStreamWriter (. conn getOutputStream ))
(write (nth body 0) 0 (count (nth body 0))) (flush) (close))))
(let [rcode (. conn getResponseCode)
rmsg (. conn getResponseMessage)
is (. conn getInputStream)
buf-len 8192
buf (make-array (. Byte TYPE) buf-len)
#^ByteArrayOutputStream bos (new ByteArrayOutputStream)
headers (into {} (. conn getHeaderFields))]
(loop []
(let [ nread (. is (read buf 0 buf-len)) ]
(when (> nread -1)
(. bos (write buf 0 nread))
(let [ bar (. bos toByteArray) ]
(. is close)
(. bos close)
(. conn disconnect)
{:return-code rcode :return-message rmsg :body bar :header headers}))))))

(pr (new String ((url-do "" "GET" { :read-timeout 5000 }) :body) "UTF-8"))
(pr (url-do "" "GET" { :read-timeout 5000 :connect-timeout 1000 :http-proxy "" }))
(pr (url-do "" "GET" { :read-timeout 5000 :connect-timeout 1000 :http-proxy "" }))

I should probably submit this back to the group, but again, newb (and running against r1097).

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