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;;; http/agent.clj: agent-based asynchronous HTTP client
;; by Stuart Sierra, http://stuartsierra.com/
;; June 8, 2009
;; Copyright (c) Stuart Sierra, 2009. All rights reserved. The use
;; and distribution terms for this software are covered by the Eclipse
;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;; which can be found in the file epl-v10.html 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.
(ns #^{:doc "Agent-based asynchronous HTTP client."}
clojure.contrib.http.agent
(:require [clojure.contrib.http.connection :as c]
[clojure.contrib.duck-streams :as duck]))
(defn- setup-http-connection
[conn options]
(.setRequestMethod conn (:method options))
(.setInstanceFollowRedirects conn (:follow-redirects options))
(doseq [[name value] (:headers options)]
(.setRequestProperty conn name value)))
(defn- success? [conn]
;; Is the response in the 2xx range?
(= 2 (unchecked-divide (.getResponseCode conn) 100)))
(defn- do-http-agent-request [state options]
(let [conn (::connection state)]
(setup-http-connection conn options)
(c/start-http-connection conn (:body options))
(let [bytes (if (success? conn)
(duck/to-byte-array (.getInputStream conn))
(duck/to-byte-array (.getErrorStream conn)))]
(.disconnect conn)
(assoc state
::response-body-bytes bytes
::state ::completed))))
(def *http-request-defaults*
{:method "GET"
:headers {}
:body nil
:connect-timeout 0
:read-timeout 0
:follow-redirects true})
(defn- completed-watch [success-fn failure-fn key http-agnt old-state new-state]
(when (and (= (::state new-state) ::completed)
(not= (::state old-state) ::completed))
(if (success? (::connection new-state))
(when success-fn (success-fn http-agnt))
(when failure-fn (failure-fn http-agnt)))))
(defn http-agent
"Creates (and immediately returns) an Agent representing an HTTP
request running in a new thread.
options are key/value pairs:
:method string
The HTTP method name. Default is \"GET\".
:headers h
HTTP headers, as a Map or a sequence of pairs like
([key1,value1], [key2,value2]) Default is nil.
:body b
HTTP request entity body, one of nil, String, byte[], InputStream,
Reader, or File. Default is nil.
:connect-timeout int
Timeout value, in milliseconds, when opening a connection to the
URL. Default is zero, meaning no timeout.
:read-timeout int
Timeout value, in milliseconds, when reading data from the
connection. Default is zero, meaning no timeout.
:follow-redirects boolean
If true, HTTP 3xx redirects will be followed automatically. Default
is true.
:on-success f
Function to be called when the request succeeds with a 2xx response
code. Default is nil, do nothing. The function will be called with
the HTTP agent as its argument. Any exceptions thrown by this
function will be added to the agent's error queue (see
agent-errors).
:on-failure f
Function to be called when the request fails with a 4xx or 5xx
response code. Default is nil, do nothing. The function will be
called with the HTTP agent as its argument. Any exceptions thrown
by this function will become agent-errors. Any exceptions thrown by
this function will be added to the agent's error queue (see
agent-errors).
"
([url & options]
(let [opts (merge *http-request-defaults* (apply array-map options))]
(let [a (agent {::connection (c/http-connection url)
::state ::created
::url url
::options opts})]
(when (or (:on-success opts) (:on-failure opts))
(add-watch a ::completed-watch
(partial completed-watch
(:on-success opts) (:on-failure opts))))
(send-off a do-http-agent-request opts)))))
(defn response-body-bytes
"Returns a Java byte array of the content returned by the server."
[a]
(when (= (::state @a) ::completed)
(::response-body-bytes @a)))
(defn response-body-str
"Returns the HTTP response body as a string. The string will be
created using the encoding specified by the server, or
*default-encoding* if it is not specified."
[a]
(let [da @a]
(when (= (::state da) ::completed)
(let [conn (::connection da)
bytes (::response-body-bytes da)
encoding (or (.getContentEncoding conn)
duck/*default-encoding*)]
(String. bytes encoding)))))
(defn response-status
"Returns the Integer response status code (e.g. 200, 404) for this request."
[a]
(when (= (::state @a) ::completed)
(.getResponseCode (::connection @a))))
(defn response-message
"Returns the HTTP response message (e.g. 'Not Found'), for this request."
[a]
(when (= (::state @a) ::completed)
(.getResponseMessage (::connection @a))))
(defn response-headers
"Returns a String=>String map of HTTP response headers. Header
names are converted to all lower-case. If a header appears more
than once, only the last value is returned."
[a]
(reduce (fn [m [#^String k v]]
(assoc m (when k (.toLowerCase k)) (last v)))
{} (.getHeaderFields (::connection @a))))
(defn response-headers-seq
"Returns the HTTP response headers in order as a sequence of
[String,String] pairs. The first 'header' name may be null for the
HTTP status line."
[http-agnt]
(let [conn (::connection @http-agnt)
f (fn thisfn [i]
;; Get value first because first key may be nil.
(when-let [value (.getHeaderField conn i)]
(cons [(.getHeaderFieldKey conn i) value]
(thisfn (inc i)))))]
(lazy-seq (f 0))))
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