DRAKMA - A Common Lisp web client


 

Abstract

Drakma is a fully-featured web client (implemented in Common Lisp) that knows how to handle HTTP/1.1 chunking, persistent connections, re-usable sockets, SSL, continuable uploads, file uploads, cookies, and other things. And it's probably a result of my NIH syndrome...

Drakma was developed and tested with LispWorks, but it should also work with a couple of other Common Lisp implementations depending on the supporting libraries. Some tests with SBCL seem to confirm this.

The code comes with a BSD-style license so you can basically do with it whatever you want.

Download shortcut: http://weitz.de/files/drakma.tar.gz.


 

Contents

  1. Examples
  2. Download and installation
  3. Support and mailing lists
  4. The Drakma dictionary
    1. The request
      1. http-request
      2. *drakma-default-external-format*
      3. *text-content-types*
      4. *body-format-function*
      5. *header-stream*
    2. Cookies
      1. cookie
      2. cookie-name
      3. cookie-value
      4. cookie-domain
      5. cookie-path
      6. cookie-expires
      7. cookie-securep
      8. cookie-http-only-p
      9. cookie-jar
      10. cookie-jar-cookies
      11. cookie=
      12. delete-old-cookies
      13. *allow-dotless-cookie-domains-p*
      14. *ignore-unparseable-cookie-dates-p*
      15. *remove-duplicate-cookies-p*
      16. parse-cookie-date
    3. Headers
      1. header-value
      2. split-tokens
      3. read-tokens-and-parameters
      4. parameter-present-p
      5. parameter-value
      6. get-content-type
    4. Conditions
      1. drakma-condition
      2. drakma-error
      3. drakma-warning
      4. syntax-error
      5. parameter-error
      6. cookie-error
      7. cookie-error-cookie
      8. cookie-date-parse-error
  5. Potential problems
  6. Acknowledgements

 

Examples

Here's an example session with Drakma 0.3.0 which demonstrates some of its features. (Some linebreaks were added or removed to enhance legibility.) Note that this doesn't necessarily reflect the current versions of Drakma and Hunchentoot. The examples should work nevertheless - kind of...
;; create a log file of this sessions
CL-USER 1 > (dribble "/tmp/drakma_dribble")
; Loading C:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\ccl\dribble.ofasl on demand...

;; load Drakma
CL-USER 2 > (asdf:oos 'asdf:load-op :drakma)
; loading system definition from c:\home\lisp\drakma\drakma.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\drakma\drakma.asd
; registering #<SYSTEM :DRAKMA 21D6D24F> as DRAKMA
;; Creating system COMMON-LISP-USER::DRAKMA
; loading system definition from c:\home\lisp\chunga\chunga.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\chunga\chunga.asd
; registering #<SYSTEM :CHUNGA 200B12A3> as CHUNGA
;; Creating system COMMON-LISP-USER::CHUNGA
; loading system definition from c:\home\lisp\flexi-streams\flexi-streams.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\flexi-streams\flexi-streams.asd
; registering #<SYSTEM :FLEXI-STREAMS 200E8017> as FLEXI-STREAMS
;; Creating system COMMON-LISP-USER::FLEXI-STREAMS
; loading system definition from c:\home\lisp\trivial-gray-streams\trivial-gray-streams.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\trivial-gray-streams\trivial-gray-streams.asd
; registering #<SYSTEM :TRIVIAL-GRAY-STREAMS 21D6741F> as TRIVIAL-GRAY-STREAMS
;; Creating system COMMON-LISP-USER::TRIVIAL-GRAY-STREAMS
; loading system definition from c:\home\lisp\cl-base64-3.3.2\cl-base64.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\cl-base64-3.3.2\cl-base64.asd
; registering #<SYSTEM CL-BASE64 21D6D277> as CL-BASE64
;; Creating system COMMON-LISP-USER::CL-BASE64
; registering #<SYSTEM CL-BASE64-TESTS 2009701B> as CL-BASE64-TESTS
;; Creating system COMMON-LISP-USER::CL-BASE64-TESTS
; loading system definition from c:\home\lisp\puri-1.5\puri.asd into
; #<The ASDF0 package, 0/16 internal, 0/16 external>
; Loading text file c:\home\lisp\puri-1.5\puri.asd
; registering #<SYSTEM PURI 21D6B093> as PURI
;; Creating system COMMON-LISP-USER::PURI
; registering #<SYSTEM PURI-TESTS 200CFEEF> as PURI-TESTS
;; Creating system COMMON-LISP-USER::PURI-TESTS
; Loading fasl file c:\home\lisp\trivial-gray-streams\package.ofasl
; Loading fasl file c:\home\lisp\trivial-gray-streams\mixin.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\packages.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\ascii.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\iso-8859.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\code-pages.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\specials.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\util.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\external-format.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\in-memory.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\stream.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\output.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\input.ofasl
; Loading fasl file c:\home\lisp\flexi-streams\strings.ofasl
; Loading fasl file c:\home\lisp\chunga\packages.ofasl
; Loading fasl file c:\home\lisp\chunga\specials.ofasl
; Loading fasl file c:\home\lisp\chunga\util.ofasl
; Loading fasl file c:\home\lisp\chunga\read.ofasl
; Loading fasl file c:\home\lisp\chunga\streams.ofasl
; Loading fasl file c:\home\lisp\chunga\input.ofasl
; Loading fasl file c:\home\lisp\chunga\output.ofasl
; Loading fasl file c:\home\lisp\cl-base64-3.3.2\package.ofasl
; Loading fasl file c:\home\lisp\cl-base64-3.3.2\encode.ofasl
; Loading fasl file c:\home\lisp\cl-base64-3.3.2\decode.ofasl
; Loading fasl file c:\home\lisp\puri-1.5\src.ofasl
; Loading fasl file c:\home\lisp\drakma\packages.ofasl
; Loading fasl file c:\home\lisp\drakma\specials.ofasl
; Loading fasl file c:\home\lisp\drakma\util.ofasl
; Loading c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\comm-defsys.lisp on demand...
;; Creating system COMM

;  Loading text file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\comm-pkg.lisp
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\sockets.ofasl
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\ssl-constants.ofasl
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\ssl-foreign-types.ofasl
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\ssl.ofasl
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\load-on-demand\processes\ssl-certs.ofasl
;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\patches\comm\0001\0001.ofasl
; Loaded public patch COMM 1.1

;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\patches\comm\0001\0002.ofasl
; Loaded public patch COMM 1.2

;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\patches\comm\0001\0003.ofasl
; Loaded public patch COMM 1.3

;  Loading fasl file c:\Program Files\LispWorks\lib\5-0-0-0\patches\comm\0001\0004.ofasl
; Loaded public patch COMM 1.4

; Loading fasl file c:\home\lisp\drakma\read.ofasl
; Loading fasl file c:\home\lisp\drakma\cookies.ofasl
; Loading fasl file c:\home\lisp\drakma\request.ofasl
NIL

;; create a package to work in
CL-USER 3 > (defpackage :drakma-user (:use :cl :drakma))
#<The DRAKMA-USER package, 0/16 internal, 0/16 external>

;; switch to this package
CL-USER 4 > (in-package :drakma-user)
#<The DRAKMA-USER package, 0/16 internal, 0/16 external>

;; log headers, so we can see what happens -
;; output to *HEADER-STREAM* will be shown in green below
DRAKMA-USER 5 > (setq *header-stream* *standard-output*)
#<Broadcast stream to (#<Echo Stream Input = #<EDITOR::RUBBER-STREAM #<EDITOR:BUFFER CAPI interactive-pane 2> 2198ECD7>,
                                     Output = #<STREAM::LATIN-1-FILE-STREAM c:\tmp\drakma_dribble>>
                       #<EDITOR::RUBBER-STREAM #<EDITOR:BUFFER CAPI interactive-pane 2> 2198ECD7>)>

;; note how Drakma automatically follows the 301 redirect and how the fourth return value shows the new URI
DRAKMA-USER 6 > (http-request "http://lisp.org/")
GET / HTTP/1.1
Host: lisp.org
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 301  Moved Permanently
Date: Sat, 26 Aug 2006 15:46:31 GMT
Connection: Close
Server: AllegroServe/1.2.37
Transfer-Encoding: chunked
LOCATION: /index.html

GET /index.html HTTP/1.1
Host: lisp.org
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200  OK
Date: Sat, 26 Aug 2006 15:46:32 GMT
Connection: Close
Server: AllegroServe/1.2.37
Content-Type: text/html
Content-Length: 82
LAST-MODIFIED: Mon, 16 Feb 2004 09:30:02 GMT

"<title>redirect...</title>
<meta http-equiv=\"Refresh\" content=\"0; url=/alu/home\">
"
200
((:DATE . "Sat, 26 Aug 2006 15:46:32 GMT")
 (:CONNECTION . "Close")
 (:SERVER . "AllegroServe/1.2.37")
 (:CONTENT-TYPE . "text/html")
 (:CONTENT-LENGTH . "82")
 (:LAST-MODIFIED . "Mon, 16 Feb 2004 09:30:02 GMT"))
#<URI http://lisp.org/index.html>
#<FLEXI-STREAMS:FLEXI-IO-STREAM 201017D3>
T

;; here, Drakma automatically interprets the 'charset=utf-8' part correctly -
;; might look a bit different in your listener depending on the font you've chosen
DRAKMA-USER 7 > (subseq (http-request "http://www.cl.cam.ac.uk/~mgk25/ucs/examples/digraphs.txt") 0 298)
GET /~mgk25/ucs/examples/digraphs.txt HTTP/1.1
Host: www.cl.cam.ac.uk
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 16:02:56 GMT
Server: Apache/1.3.37 (Unix) mod_ucam_webauth/1.2.2
Last-Modified: Thu, 05 Jan 2006 20:49:55 GMT
ETag: "17cd62-298-43bd8673"
Accept-Ranges: bytes
Content-Length: 664
Connection: close
Content-Type: text/plain; charset=utf-8

"Latin Digraphs and Ligatures in ISO10646-1

A short table of ligatures and digraphs follows. Some of these may not be
ligatures/digraphs in the technical sense, (for example,  is a seperate
letter in English), but visually they behave that way.

AE : U+00C6
ae : U+00E6
ſs : U+00DF
IIJJ : U+0132"

;; a vector of octets is returned for (non-text) binary data - a picture in this case
DRAKMA-USER 8 > (http-request "http://zappa.com/favicon.ico")
GET /favicon.ico HTTP/1.1
Host: zappa.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 16:02:59 GMT
Server: Apache/2.0.46 (Red Hat)
Last-Modified: Fri, 17 Mar 2006 08:11:07 GMT
ETag: "3a4080-b6-59d5bcc0"
Accept-Ranges: bytes
Content-Length: 182
Connection: close
Content-Type: image/gif

#(71 73 70 56 57 97 17 0 17 0 179 1 0 150 151 153 255 255 255 37 37 36 112 114 115
  201 202 204 0 0 0 80 83 84 26 28 26 230 231 231 249 249 249 12 13 14 219 221 222
  18 21 22 239 240 241 52 52 54 64 66 66 33 249 4 1 0 0 1 0 44 0 0 0 0 17 0 17 0 0
  4 99 48 200 73 107 109 54 172 101 129 120 196 180 12 12 51 80 64 161 42 3 48 28
  170 106 72 141 16 223 120 113 166 121 95 0 14 95 239 33 236 41 98 10 129 114 185
  188 29 127 25 201 224 73 60 4 8 0 130 22 59 64 52 96 135 148 35 96 80 152 159 186
  192 64 183 112 0 200 61 65 0 1 192 76 214 185 113 102 241 88 26 90 8 81 18 8 94 
  130 134 22 17 0 59)
200
((:DATE . "Sat, 26 Aug 2006 16:02:59 GMT")
 (:SERVER . "Apache/2.0.46 (Red Hat)")
 (:LAST-MODIFIED . "Fri, 17 Mar 2006 08:11:07 GMT")
 (:ETAG . "\"3a4080-b6-59d5bcc0\"")
 (:ACCEPT-RANGES . "bytes")
 (:CONTENT-LENGTH . "182")
 (:CONNECTION . "close")
 (:CONTENT-TYPE . "image/gif"))
#<URI http://zappa.com/favicon.ico>
#<FLEXI-STREAMS:FLEXI-IO-STREAM 200D59BF>
T

;; a secure connection (see below) -
;; also note that the server uses chunked transfer encoding for its reply
DRAKMA-USER 9 > (ppcre:scan-to-strings "(?s)You have.*your data."
                                       (http-request "https://www.fortify.net/cgi/ssl_2.pl"))
GET /cgi/ssl_2.pl HTTP/1.1
Host: www.fortify.net
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 16:10:06 GMT
Server: Apache
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html


"You have connected to this web server using the DHE-RSA-AES256-SHA encryption cipher
 with a key length of 256 bits.
 <p>
 This is a high-grade encryption connection, regarded by most experts as being suitable
 for sending or receiving even the most sensitive or valuable information
 across a network.
 <p>
 In a crude analogy, using this cipher is similar to sending or storing your data inside
 a high quality safe - compared to an export-grade cipher which is similar to using
 a paper envelope to protect your data."
#()

;; using a different 'User-Agent' header
DRAKMA-USER 10 > (ppcre:regex-replace-all
                  "<.*?>"
                  (ppcre:scan-to-strings "(?s)Your browser reports.*?</table>" 
                                         (http-request "http://bcheck.scanit.be/bcheck/"
                                                       :user-agent :explorer))
                  "")
GET /bcheck/ HTTP/1.1
Host: bcheck.scanit.be
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 16:21:50 GMT
Server: Apache
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html


"Your browser reports to be:

Browser name: MSIE
Version: 6.0
Platform: Windows NT 5.1
"

;; sending parameters in a POST request and working with cookies -
;; note how Drakma sends the cookie back in the second request
DRAKMA-USER 11 > (let ((cookie-jar (make-instance 'cookie-jar)))
                   (http-request "http://www.phpsecurepages.com/test/test.php"
                                 :method :post
                                 :parameters '(("entered_login" . "test")
                                               ("entered_password" . "test"))
                                 :cookie-jar cookie-jar)
                   (http-request "http://www.phpsecurepages.com/test/test2.php"
                                 :cookie-jar cookie-jar)
                   (cookie-jar-cookies cookie-jar))
POST /test/test.php HTTP/1.1
Host: www.phpsecurepages.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Content-Length: 40
Content-Type: application/x-www-form-urlencoded
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 18:26:17 GMT
Server: Apache/2.0.51 (Fedora)
X-Powered-By: PHP/4.3.10
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Set-Cookie: PHPSESSID=3ce33aa3e326ab4bf5da7feecc3248b4; path=/
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html


GET /test/test2.php HTTP/1.1
Host: www.phpsecurepages.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Cookie: PHPSESSID=3ce33aa3e326ab4bf5da7feecc3248b4
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 18:26:18 GMT
Server: Apache/2.0.51 (Fedora)
X-Powered-By: PHP/4.3.10
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html


(#<COOKIE PHPSESSID=3ce33aa3e326ab4bf5da7feecc3248b4; path=/; domain=www.phpsecurepages.com>)

;; now we are going to re-use a socket for the second connection to the same server
;; this will also work with chunked encoding
DRAKMA-USER 12 > (let ((stream (nth-value 4 (http-request "http://www.lispworks.com/" :close nil))))
                   (nth-value 2 (http-request "http://www.lispworks.com/success-stories/index.html"
                                              :stream stream)))
GET / HTTP/1.1
Host: www.lispworks.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 18:34:20 GMT
Server: Apache/1.3.37 Ben-SSL/1.57 (Unix)
Last-Modified: Tue, 08 Aug 2006 18:20:49 GMT
ETag: "28ee4f0-22db-44d8d601"
Accept-Ranges: bytes
Content-Length: 8923
Content-Type: text/html

GET /success-stories/index.html HTTP/1.1
Host: www.lispworks.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Date: Sat, 26 Aug 2006 18:34:20 GMT
Server: Apache/1.3.37 Ben-SSL/1.57 (Unix)
Last-Modified: Tue, 08 Aug 2006 18:22:19 GMT
ETag: "28f3f42-2325-44d8d65b"
Accept-Ranges: bytes
Content-Length: 8997
Connection: close
Content-Type: text/html

((:DATE . "Sat, 26 Aug 2006 18:34:20 GMT")
 (:SERVER . "Apache/1.3.37 Ben-SSL/1.57 (Unix)")
 (:LAST-MODIFIED . "Tue, 08 Aug 2006 18:22:19 GMT")
 (:ETAG . "\"28f3f42-2325-44d8d65b\"")
 (:ACCEPT-RANGES . "bytes")
 (:CONTENT-LENGTH . "8997")
 (:CONNECTION . "close")
 (:CONTENT-TYPE . "text/html"))

;; testing basic authorization against a local Hunchentoot server
DRAKMA-USER 13 > (nth-value 1 (http-request "http://localhost:4242/tbnl/test/authorization.html"))
GET /tbnl/test/authorization.html HTTP/1.1
Host: localhost:4242
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 401 Authorization Required
Content-Length: 563
Content-Type: text/html; charset=iso-8859-1
Date: Sat, 26 Aug 2006 18:38:58 GMT
Server: Hunchentoot 0.1.5 (TBNL 0.10.0)
Connection: Close
WWW-Authenticate: Basic realm="TBNL"

401

DRAKMA-USER 14 > (nth-value 1 (http-request "http://localhost:4242/tbnl/test/authorization.html"
                                            :basic-authorization '("nanook" "igloo")))
GET /tbnl/test/authorization.html HTTP/1.1
Host: localhost:4242
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Authorization: Basic bmFub29rOmlnbG9v
Accept: */*
Connection: close

HTTP/1.1 200 OK
Content-Length: 884
Content-Type: text/html; charset=iso-8859-1
Date: Sat, 26 Aug 2006 18:39:19 GMT
Server: Hunchentoot 0.1.5 (TBNL 0.10.0)
Connection: Close

200

;; now we ask Drakma to return a stream and read from it directly
DRAKMA-USER 15 > (let ((stream (http-request "http://www.jalat.com/blogs/lisp?id=3" 
                                             :want-stream t)))
                   (loop for i below 41
                         for line = (read-line stream)
                         when (> i 35)
                         do (write-line line))
                   (close stream)
                   (values))
GET /blogs/lisp?id=3 HTTP/1.1
Host: www.jalat.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close

HTTP/1.1 200 OK
Content-Length: 21453
Content-Type: text/html; charset=iso-8859-1
Date: Sat, 26 Aug 2006 19:53:37 GMT
Server: Hunchentoot 0.1.3 (TBNL 0.9.7)
Connection: Close

Bill Clementson has <a
href="http://bc.tech.coop/blog/041111.html">written</a> about getting
TBNL up and running with apache and mod_lisp. In this example I'm
going to use <a href="http://weitz.de/hunchentoot/">hunchentoot</a>, a
pure lisp web server by (again) Edi Weitz.

;; let's test a POST request without content length and with chunked transfer encoding -
;; we build the content in several steps using different types of data
;; (note: doesn't work anymore, probably due to server changes)
DRAKMA-USER 16 > (let ((temp-file (ensure-directories-exist #p"/tmp/quux.txt"))
                       (continuation (http-request "http://meme.b9.com/login.html"
                                                   :method :post
                                                   :content :continuation)))
                   (funcall continuation "username=" t)
                   (funcall continuation (list (char-code #\n) (char-code #\a)) t)
                   (funcall continuation (lambda (stream)
                                           (write-char #\n stream)) t)
                   (with-open-file (out temp-file
                                        :direction :output
                                        :if-does-not-exist :create
                                        :if-exists :supersede)
                     (write-string "ook" out))
                   (funcall continuation temp-file t)
                   (ppcre:scan-to-strings "(?i)[a-z ]+nanook[a-z .]+"
                                          (funcall continuation "&password=igloo")))
POST /login.html HTTP/1.1
Host: meme.b9.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close
Content-Type: application/x-www-form-urlencoded
Transfer-Encoding: chunked

HTTP/1.0 200 OK
Date: Sat, 02 Sep 2006 00:25:24 GMT
Connection: close
Server: AllegroServe/1.2.45
Content-Type: text/html
Content-Length: 2922
PRAGMA: no-cache
CACHE-CONTROL: no-cache
SET-COOKIE: meme=1834b91d26f9be983a0ed9ca; path=/

"The username nanook is not in our database."
#()

;; finally, we send additional headers to ask for a range
DRAKMA-USER 17 > (ppcre:regex-replace-all
                  "<.*?>"
                  (format nil "~A~A"
                          (http-request "http://users.cableaz.com/~lantz/pages/hunchentoot.html"
                                        :additional-headers '(("Range" . "bytes=959-999")))
                          (http-request "http://users.cableaz.com/~lantz/pages/hunchentoot.html"
                                        :additional-headers '(("Range" . "bytes=1165-1201"))))
                  "")
GET /~lantz/pages/hunchentoot.html HTTP/1.1
Host: users.cableaz.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close
Range: bytes=959-999

HTTP/1.1 206 Partial Content
Date: Sat, 26 Aug 2006 19:07:44 GMT
Server: Apache/2.0.16 (Unix)
Last-Modified: Sun, 24 Apr 2005 04:08:45 GMT
ETag: "35298d-2fea-d8f4cd40"
Accept-Ranges: bytes
Content-Length: 41
Content-Range: bytes 959-999/12266
Content-Type: text/html; charset=ISO-8859-1
Connection: close

GET /~lantz/pages/hunchentoot.html HTTP/1.1
Host: users.cableaz.com
User-Agent: Drakma/0.3.0 (LispWorks 5.0.0; Windows NT; Windows XP: 5.1 (build 2600) Service Pack 2; http://weitz.de/drakma/)
Accept: */*
Connection: close
Range: bytes=1165-1201

HTTP/1.1 206 Partial Content
Date: Sat, 26 Aug 2006 19:07:45 GMT
Server: Apache/2.0.16 (Unix)
Last-Modified: Sun, 24 Apr 2005 04:08:45 GMT
ETag: "35298d-2fea-d8f4cd40"
Accept-Ranges: bytes
Content-Length: 37
Content-Range: bytes 1165-1201/12266
Content-Type: text/html; charset=ISO-8859-1
Connection: close

"DRAKMA (Queen of Cosmic Greed)
HUNCHENTOOT (The Giant Spider)"

 

Download and installation

Drakma together with this documentation can be downloaded from http://weitz.de/files/drakma.tar.gz. The current version is 1.2.3. Drakma can be installed via ASDF and depends on the open source libraries CL-BASE64 (use 3.3.2 or higher to avoid an unneeded dependency on KMRCL), Puri (1.5.5 or higher), FLEXI-STREAMS, and Chunga (1.1.0 or higher). If you're not using LispWorks, you'll also need usocket (0.3.2 or newer) and (except for AllegroCL) CL+SSL. Try to use the newest versions of all these libraries - use the CVS versions if in doubt. Installation via asdf-install should also be possible, and there's a port for Gentoo Linux thanks to Matthew Kennedy.

For SSL, you will need to have the corresponding C libraries as well. You'll usually have them already unless you're on Windows.

Luís Oliveira maintains a darcs repository of Drakma at http://common-lisp.net/~loliveira/ediware/.

A Mercurial repository of older versions is available at http://arcanes.fr.eu.org/~pierre/2007/02/weitz/ thanks to Pierre Thierry.
 

Support and mailing lists

For questions, bug reports, feature requests, improvements, or patches please use the drakma-devel mailing list. If you want to be notified about future releases subscribe to the drakma-announce mailing list. These mailing lists were made available thanks to the services of common-lisp.net.

If you want to send patches, please read this first.
 

The Drakma dictionary

The request

The HTTP-REQUEST function is the heart of Drakma. It is used to send requests to web servers and will either return the message body of the server's reply or (if the user so wishes) a stream one can read from. The wealth of keyword parameters might look a bit intimidating first, but you will rarely need more than two or three of them - the default behaviour of Drakma is (hopefully) designed to do The Right Thing[TM] in most cases.

You can use the *HEADER-STREAM* variable to debug requests handled by Drakma in a way similar to LiveHTTPHeaders.


[Function]
http-request uri &key protocol method force-ssl parameters form-data content content-length content-type cookie-jar basic-authorization user-agent accept proxy proxy-basic-authorization additional-headers redirect redirect-methods auto-referer keep-alive close external-format-out external-format-in force-binary want-stream stream connection-timeout read-timeout write-timeout deadline
=> body-or-stream, status-code, headers, uri, stream, must-close, reason-phrase


Sends an HTTP request to a web server and returns its reply. uri is where the request is sent to, and it is either a string denoting a uniform resource identifier or a PURI:URI object. The scheme of uri must be 'http' or 'https'. The function returns seven values - the body of the reply (but see below), the status code as an integer, an alist of the headers sent by the server where for each element the car (the name of the header) is a keyword and the cdr (the value of the header) is a string, the URI the reply comes from (which might be different from the URI the request was sent to in case of redirects), the stream the reply was read from, a generalized boolean which denotes whether the stream should be closed (and which you can usually ignore), and finally the reason phrase from the status line as a string.

protocol is the HTTP protocol which is going to be used in the request line, it must be one of the keywords :HTTP/1.0 or :HTTP/1.1 (the default). method is the method used in the request line, a keyword (like :GET or :HEAD) denoting a valid HTTP/1.1 or WebDAV request method. Additionally, you can also use the pseudo method :OPTIONS* which is like :OPTIONS but means that an "OPTIONS *" request line will be sent, i.e. the URI's path and query parts will be ignored.

If force-ssl is true, SSL will be attached to the socket stream which connects Drakma with the web server. Usually, you don't have to provide this argument, as SSL will be attached anyway if the scheme of uri is 'https'.

parameters is an alist of name/value pairs (the car and the cdr each being a string) which denotes the parameters which are added to the query part of the URI or (in the case of a POST request) comprise the request body. (But see content below.) The values can also be NIL in which case only the name (without an equal sign) is used in the query string. The name/value pairs are URL-encoded using the external format external-format-out before they are sent to the server, unless form-data is true in which case the POST request body is sent as multipart/form-data using external-format-out. The values of the parameters alist can also be pathnames, unary functions, open binary input streams, or lists where the first element is of one of the former types. These values denote files which should be sent as part of the request body. If such file designators are present in parameters, the content type of the request is always multipart/form-data. If the value denoting a file is a list, the part of the list behind the first element is treated as a plist which can be used to optionally specify a content type (the default is "application/octet-stream") and/or a filename (the default is the result of applying FILE-NAMESTRING to the pathname) for the file. So, for example, a full file upload request could look like this:

(http-request "http://www.whatever.com/file_upload/"
              :method :post
              ;; the following line is only needed if the receiving server doesn't accept
              ;; chunked transfer encoding (like for example Apache 1.x)
              :content-length t
              :parameters '(("file1" #p"/tmp/top_secret_stuff.doc" :content-type "application/msword" :filename "upload.doc")
                            ("file2" . #p"/tmp/portrait.jpg")
                            ("lname" . "Duck") ("fname" . "Donald")))

external-format-out (the default is the value of *DRAKMA-DEFAULT-EXTERNAL-FORMAT*) must be the name of a FLEXI-STREAMS external format.

content, if not NIL, is used as the request body - parameters is ignored in this case. content can be a string, a sequence of octets, a pathname, an open binary input stream, or a function designator. If content is a sequence, it will be directly sent to the server (using external-format-out in the case of strings). If content is a pathname, the binary contents of the corresponding file will be sent to the server. If content is a stream, everything that can be read from the stream until EOF will be sent to the server. If content is a function designator, the corresponding function will be called with one argument, the stream to the server, to which it should send data.

Finally, content can also be the keyword :CONTINUATION in which case HTTP-REQUEST returns only one value - a "continuation" function. This function has one required argument and one optional argument. The first argument will be interpreted like content above (but it cannot be a keyword), i.e. it will be sent to the server according to its type. If the second argument is true, the continuation function can be called again to send more content, if it is NIL, the continuation function returns what HTTP-REQUEST would have returned. See above for an example on how to use a continuation function and different types of content.

If content is a sequence, Drakma will use LENGTH to determine its length and will use the result for the 'Content-Length' header sent to the server. You can overwrite this with the content-length parameter (a non-negative integer) which you can also use for the cases where Drakma can't or won't determine the content length itself. You can also explicitly provide a content-length argument of NIL which will imply that no 'Content-Length' header will be sent even if Drakma could compute the value. If no 'Content-Length' header is sent, Drakma will use chunked encoding to send the content body. Note that this will not work with some older web servers.

Providing a true CONTENT-LENGTH argument which is not a non-negative integer means that Drakma must build the request body in RAM and compute the content length even if it would have otherwise used chunked encoding, for example in the case of file uploads.

content-type is the corresponding 'Content-Type' header to be sent and will be ignored unless content is provided as well.

Note that a query already contained in uri will always be sent with the request line anyway in addition to other parameters sent by Drakma.

cookie-jar is a cookie jar containing cookies which will potentially be sent to the server (if the domain matches, if they haven't expired, etc.) - this cookie jar will be modified according to the 'Set-Cookie' header(s) sent back by the server.

basic-authorization, if not NIL, should be a list of two strings (username and password) which will be sent to the server for basic authorization. If you want to use non-ASCII characters here, look at Christian Haselbach's CL-RFC2047 library. See here for a (server-side) code example.

user-agent, if not NIL, denotes which 'User-Agent' header will be sent with the request. It can be one of the keywords :DRAKMA (the default), :FIREFOX, :EXPLORER, :OPERA, or :SAFARI which denote the current version of Drakma or, in the latter four cases, a fixed string corresponding to a more or less recent (as of August 2006) version of the corresponding browser. Or it can be a string which is used directly. accept, if not NIL, is the 'Accept' header sent - the default is "*/*".

If proxy is not NIL, it should be a string denoting a proxy server through which the request should be sent. Or it can be a list of two values - a string denoting the proxy server and an integer denoting the port to use (which will default to 80 otherwise). proxy-basic-authorization is used like basic-authorization, but for the proxy, and only if proxy is true.

additional-headers is a name/value alist of additional HTTP headers which should be sent with the request. Unlike in parameters, the cdrs can not only be strings but also designators for unary functions (which should in turn return a string) in which case the function is called each time the header is written.

If redirect is not NIL, it must be a non-negative integer or T. If redirect is true, Drakma will follow redirects (return codes 301, 302, 303, or 307) unless redirect is 0. If redirect is an integer, it will be decreased by 1 with each redirect. Drakma will only follow redirects if method is a member of the list redirect-methods the initial value of which is (:GET :HEAD). Furthermore, if auto-referer is true when following redirects, Drakma will populate the 'Referer' (sic!) header with the URI that triggered the redirection, overwriting an existing 'Referer' header (in additional-headers) if necessary.

If keep-alive is T, the server will be asked to keep the connection alive, i.e. not to close it after the reply has been sent. (Note that this not necessary if both the client and the server use HTTP 1.1.) If close is T, the server is explicitly asked to close the connection after the reply has been sent. keep-alive and close are obviously mutually exclusive. The default for close is T, the default for keep-alive is NIL.

HTTP-REQUEST will always close the stream to the server before it returns unless want-stream is true or if the headers exchanged between Drakma and the server determine that the connection will be kept alive - for example if both client and server used the HTTP 1.1 protocol and no explicit "Connection: close" header was sent. In these cases you will have to close the stream manually.

If the message body sent by the server has a text content type, Drakma will try to return it as a Lisp string. It'll first check if the 'Content-Type' header denotes an encoding (charset) to be used, or otherwise it will use the external-format-in (the default is the value of *DRAKMA-DEFAULT-EXTERNAL-FORMAT*) argument. The body is decoded using FLEXI-STREAMS. If FLEXI-STREAMS doesn't know the external format, the body is returned as an array of octets. If the message body doesn't have a text content type or if force-binary is true, the body is always returned as an array of octets. (But see *TEXT-CONTENT-TYPES* and *BODY-FORMAT-FUNCTION*.) If the body is empty, NIL will be returned.

If want-stream is true, the message body is not read and instead the (open) socket stream is returned as the first return value. If the sixth return value (must-close) of HTTP-REQUEST is true, Drakma deduced from the reply headers that the server will close the stream on its side, so you can't re-use it - you'll have to close it instead. Of course, no matter what the sixth return value is, it's alway your responsibility to close the stream once you're done with it. The stream returned is a flexi stream with a chunked stream as its underlying stream.

Drakma will usually create a new socket connection for each HTTP request. However, you can use the stream argument to provide an open socket stream which should be re-used instead. stream must be a stream returned by a previous invocation of HTTP-REQUEST where the sixth return value wasn't true. Obviously, it must also be connected to the correct server and at the right position (i.e. the message body, if any, must have been read). Drakma will never attach SSL to a stream provided as the stream argument.

connection-timeout is the time (in seconds) Drakma will wait until it considers an attempt to connect to a server as a failure. read-timeout and write-timeout are the read and write timeouts (in seconds) for the socket stream to the server. All three timeout arguments can also be NIL (meaning no timeout), and they don't apply if an existing stream is re-used. All timeout keyword arguments are only available for LispWorks, write-timeout is only available for LispWorks 5.0 or higher.

deadline, a time in the future, specifies the time until which the request should be finished. The deadline is specified in internal time units. If the server fails to respond until that time, a COMMUNICATION-DEADLINE-EXPIRED condition is signalled. DEADLINE is only available on CCL 1.2 and later.


[Special variable]
*drakma-default-external-format*


The default value for the two external format keyword arguments of HTTP-REQUEST. The value of this variable will be interpreted by FLEXI-STREAMS. The initial value is the keyword :LATIN-1. (Note that Drakma binds *DEFAULT-EOL-STYLE* to :LF.)


[Special variable]
*text-content-types*


A list of conses which are used by the default value of *BODY-FORMAT-FUNCTION* to decide whether a 'Content-Type' header denotes text content. The car and cdr of each cons should each be a string or NIL. A content type matches one of these entries (and thus denotes text) if the type part is STRING-EQUAL to the car or if the car is NIL and if the subtype part is STRING-EQUAL to the cdr or if the cdr is NIL.

The initial value of this variable is the list

(("text" . nil))
which means that every content type that starts with "text/" is regarded as text, no matter what the subtype is.


[Special variable]
*body-format-function*


A function which determines whether the content body returned by the server is text and should be treated as such or not. The function is called after the request headers have been read and it must accept two arguments, headers and external-format-in, where headers is like the third return value of HTTP-REQUEST while external-format-in is the HTTP-REQUEST argument of the same name. It should return NIL if the body should be regarded as binary content, or a FLEXI-STREAMS external format (which will be used to read the body) otherwise.

This function will only be called if the force-binary argument to HTTP-REQUEST is NIL.

The initial value of this variable is a function which uses *TEXT-CONTENT-TYPES* to determine whether the body is text and then proceeds as described in the HTTP-REQUEST documentation entry.


[Special variable]
*header-stream*


If this variable is not NIL, it should be bound to a stream to which incoming and outgoing headers will be written for debugging purposes.

Cookies

HTTP-REQUEST can deal with cookies if it gets a cookie jar, a collection of COOKIE objects, as its cookie-jar argument. Cookies sent by the web server will be added to the cookie jar (or updated) if appropriate and cookies already in the cookie jar will be sent to the server together with the request.

Drakma will never remove cookies from a cookie jar automatically - you have to do it manually using DELETE-OLD-COOKIES.


[Standard class]
cookie


Elements of this class represent HTTP cookies. If you need to create your own cookies, you should use MAKE-INSTANCE with the initargs :NAME, :DOMAIN, :VALUE, :PATH, :EXPIRES, :SECUREP, and :HTTP-ONLY-P all of which are optional except for the first two. The meaning of these initargs and the corresponding accessors should be pretty clear if one looks at the original cookie specification (and at this page for the HttpOnly extension).
DRAKMA-USER 18 > (make-instance 'cookie :name "Foo" 
                                        :value "Bar"
                                        :expires (+ (get-universal-time) 3600)
                                        :domain ".weitz.de")
#<COOKIE Foo=Bar; expires=Sat, 26-08-2006 23:14:27 GMT; path=/; domain=.weitz.de>


[Specialized accessors]
cookie-name (cookie cookie) => name
(setf (cookie-name (cookie cookie)) name)
cookie-value (cookie cookie) => value
(setf (cookie-value (cookie cookie)) value)
cookie-domain (cookie cookie) => domain
(setf (cookie-domain (cookie cookie)) domain)
cookie-path (cookie cookie) => path
(setf (cookie-path (cookie cookie)) path)
cookie-expires (cookie cookie) => expiry
(setf (cookie-expires (cookie cookie)) expiry)
cookie-securep (cookie cookie) => securep
(setf (cookie-securep (cookie cookie)) securep)
cookie-http-only-p (cookie cookie) => http-only-p
(setf (cookie-http-only-p (cookie cookie)) http-only-p)


These are accessors to get and set the corresponding slots of a COOKIE object. Note that expiry is a universal time and securep and http-only-p are generalized booleans. All other values are strings.


[Standard class]
cookie-jar


An object of this class encapsulates a collection (a list, actually) of COOKIE objects. You create a new cookie jar with (MAKE-INSTANCE 'COOKIE-JAR) where you can optionally provide a list of COOKIE objects with the :COOKIES initarg. The cookies in a cookie jar are accessed with COOKIE-JAR-COOKIES.


[Specialized accessor]
cookie-jar-cookies (cookie-jar cookie-jar) => list
(setf (cookie-jar-cookies (cookie-jar cookie-jar)) list)


This accessor is used to get and set the cookies comprised in a cookie jar. list is a list of COOKIE objects.

Note that list should not contain two cookies which are equal according to COOKIE=.


[Function]
cookie= cookie1 cookie2 => result


Returns true if the cookies cookie1 and cookie2 are equal. Two cookies are considered to be equal if their names and paths are equal.


[Function]
delete-old-cookies cookie-jar => cookie-jar


Removes all cookies from the cookie jar cookie-jar which have either expired or which don't have an expiry date.


[Special variable]
*allow-dotless-cookie-domains-p*


When this variable is not NIL, cookie domains containing no dots are considered valid. The default is NIL, meaning to disallow such domains except for "localhost".


[Special variable]
*ignore-unparseable-cookie-dates-p*


Whether Drakma is allowed to treat Expires dates in cookie headers as non-existent if it can't parse them. If the value of this variable is NIL (which is the default), an error of type COOKIE-DATE-PARSE-ERROR will be signalled instead.

Note that Drakma tries hard to parse every date representation its author has so far seen in the wild. As everybody and their sister seems to invent their own format, this feels like an uphill battle, though. Nevertheless, if you're confronted with something Drakma can't parse, report it to the mailing list and set this variable to a true value only as a temporary workaround.


[Function]
parse-cookie-date string => universal-time


Parses (the string representation of) a cookie expiry date string and returns it as a Lisp universal time. Currently understands the following formats:
"Wed, 06-Feb-2008 21:01:38 GMT"
"Wed, 06-Feb-08 21:01:38 GMT"
"Tue Feb 13 08:00:00 2007 GMT"
"Wednesday, 07-February-2027 08:55:23 GMT"
"Wed, 07-02-2017 10:34:45 GMT"
Instead of "GMT", time zone abbreviations like "CEST" and UTC offsets like "GMT-01:30" are also allowed.

While this function has cookie in its name, it might come in handy in other situations as well and it is thus exported as a convenience function.


[Special variable]
*remove-duplicate-cookies-p*


Determines how duplicate cookies in the response are handled, defaults to T. Cookies are considered duplicate using COOKIE=. Valid values are: Misbehaving servers may send duplicate cookies back in the same Set-Cookie header:
HTTP/1.1 200  OK
Server: My-hand-rolled-server
Date: Wed, 07 Apr 2010 15:12:30 GMT
Connection: Close
Content-Type: text/html
Content-Length: 82
Set-Cookie: a=1; Path=/; Secure, a=2; Path=/; Secure

In this case Drakma has to choose whether cookie "a" has the value "1" or "2". By default, Drakma will choose the last value specified, in this case "2".

By default, Drakma conforms to RFC2109 HTTP State Management Mechanism, section 4.3.3 Cookie Management:

If a user agent receives a Set-Cookie response header whose NAME is the same as a pre-existing cookie, and whose Domain and Path attribute values exactly (string) match those of a pre-existing cookie, the new cookie supersedes the old.

Headers

This section assembles a couple of convenience functions which can be used to access information returned as the third value (headers) of HTTP-REQUEST.

Note that if the header sends multiple headers with the same name, these are comprised into one entry by HTTP-REQUEST where the values are separated by commas.


[Function]
header-value name headers => value


If headers is an alist of headers as returned by HTTP-REQUEST and name is a keyword naming a header, this function returns the corresponding value of this header (or NIL if it's not in headers).
DRAKMA-USER 19 > (setq *header-stream* nil)
NIL
DRAKMA-USER 20 > (header-value :server
                               (nth-value 2 (http-request "http://www.jalat.com/blogs/lisp?id=5")))
"Hunchentoot 0.1.3 (TBNL 0.9.7)"


[Function]
split-tokens string => string-list


Splits the string string into a list of substrings separated by commas and optional whitespace. Empty substrings are ignored.
DRAKMA-USER 21 > (split-tokens "chunked, identity")
("chunked" "identity")


[Function]
read-tokens-and-parameters string &key value-required-p => list


Reads a comma-separated list of tokens from the string string. Each token can be followed by an optional, semicolon-separated list of attribute/value pairs where the attributes are tokens followed by a #\= character and a token or a quoted string. Returned is a list where each element is either a string (for a simple token) or a cons of a string (the token) and an alist (the attribute/value pairs). If value-required-p is NIL (the default is T), the value part (including the #\= character) of each attribute/value pair is optional.

An example of an HTTP header which uses a syntax which can be parsed with this function is the 'Transfer-Encoding' header.

DRAKMA-USER 21 > (read-tokens-and-parameters "iso-8859-5, unicode-1-1;q=0.8")
("iso-8859-5" ("unicode-1-1" ("q" . "0.8")))


[Function]
parameter-present-p name parameters => generalized-boolean


If parameters is an alist of parameters (i.e. of attribute/value pairs) as returned by, for example, READ-TOKENS-AND-PARAMETERS and name is a string naming a parameter, this function returns the full parameter (name and value) - or NIL if it's not in parameters.
DRAKMA-USER 23 > (parameter-present-p "frob" '(("charset" . "latin-1") ("frob" . "quux")))
("frob" . "quux")

DRAKMA-USER 24 > (parameter-present-p "foo" '(("charset" . "latin-1") ("frob" . "quux")))
NIL


[Function]
parameter-value name parameters => value


If parameters is an alist of parameters (i.e. of attribute/value pairs) as returned by, for example, READ-TOKENS-AND-PARAMETERS and name is a string naming a parameter, this function returns the value of this parameter - or NIL if it's not in parameters.
DRAKMA-USER 25 > (parameter-value "frob" '(("charset" . "latin-1") ("frob" . "quux")))
"quux"

DRAKMA-USER 26 > (parameter-value "foo" '(("charset" . "latin-1") ("frob" . "quux")))
NIL


[Function]
get-content-type headers => type, subtype, parameters


Reads and parses a 'Content-Type' header and returns it as three values - the type, the subtype, and an alist (possibly empty) of name/value pairs for the optional parameters. headers is supposed to be an alist of HTTP headers as returned by HTTP-REQUEST. Returns NIL if there is no 'Content-Type' header amongst headers.
DRAKMA-USER 27 > (get-content-type 
                  (nth-value 2 (http-request "http://weitz.de/")))
"text"
"html"
(("charset" . "iso-8859-1"))

Conditions

This section lists all the condition types that are defined by Drakma.


[Condition]
drakma-condition


All conditions signalled by Drakma are of this type. This is a subtype of CONDITION.


[Error]
drakma-error


All errors signalled by Drakma are of this type. This is a subtype of DRAKMA-CONDITION and of ERROR.


[Warning]
drakma-warning


All warnings signalled by Drakma are of this type. This is a subtype of DRAKMA-CONDITION and of WARNING.


[Error]
syntax-error


An error of this type is signalled if Drakma encounters wrong or unknown syntax when reading the reply from the server. This is a subtype of DRAKMA-ERROR.


[Error]
parameter-error


An error of this type is signalled if a function was called with inconsistent or illegal parameters. This is a subtype of DRAKMA-ERROR.


[Error]
cookie-error


An error of this type is signalled in case of an attempt to create a COOKIE object that's not valid. This is a subtype of DRAKMA-ERROR. The condition object contains a cookie slot which can be accessed with the COOKIE-ERROR-COOKIE reader. Note that the content of this slot can be NIL if the cookie couldn't be initialized.


[Reader]
cookie-error-cookie error => cookie-or-nil


If error is of type COOKIE-ERROR, this function will return the associated invalid cookie or NIL if the cookie couldn't be created.


[Error]
cookie-date-parse-error


An error of this type is signalled if Drakma tried to parse the date of an incoming cookie header and can't interpret it. This is a subtype of COOKIE-ERROR.

See also *IGNORE-UNPARSEABLE-COOKIE-DATES-P*.


 

Potential problems

Some web servers (notably Paul Graham's Arc web server and some very old ones) use wrong line endings when sending the HTTP headers. By default, Drakma won't be able to understand them, but see Chunga's *ACCEPT-BOGUS-EOLS*.
 

Acknowledgements

Initial versions of Drakma used code from ACL-COMPAT, specifically the chunking code from Jochen Schmidt. (This has been replaced by Chunga.) The API of Drakma's HTTP-REQUEST was inspired by John Foderaro's DO-HTTP-REQUEST. And greetings to Bob Hutchinson who already anticipated this library in 2005... :)

This documentation was prepared with DOCUMENTATION-TEMPLATE.

$Header: /usr/local/cvsrep/drakma/doc/index.html,v 1.88 2008/05/30 09:28:20 edi Exp $

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