1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Nine Nines Support: Cowboy User Guide</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!-- Change them or set them up as you like -->
<meta name="description" content="">
<meta name="author" content="(Soft10) Pol Cámara">
<!-- Stylesheets -->
<link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'>
<link href="/css/bootstrap.min.css" rel="stylesheet">
<link href="/css/99s.css" rel="stylesheet">
<!-- <link href="js/google-code-prettify/prettify.css" rel="stylesheet"> -->
<link href="/css/sh99s.css" rel="stylesheet"/>
<!-- Enables html5 support on older browsers, other js is placed at the end of the page to speed up loading -->
<!--[if lt IE 9]>
<script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>
<![endif]-->
<link rel="shortcut icon" href="/img/ico/favicon.ico">
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png">
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png">
<link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png">
<link rel="alternate" href="/feeds/atom.xml" type="application/atom+xml" title="Nine Nines Atom Feed">
</head>
<body class="big_text docs">
<header id="page-head">
<div id="topbar" class="container">
<div class="row">
<div class="span2">
<h1 id="logo"><a href="/" title="99s">99s</a></h1>
</div>
<div class="span10">
<!-- Top navigation and social icons-->
<div id="side-header">
<nav>
<ul>
<li><a title="Erlang training" href="/training">Training</a></li>
<li><a title="Technical publications" href="/articles">Articles</a></li>
<li><a title="Our talks" href="/talks">Talks</a></li>
<li class="active"><a title="Our services" href="/support">Pricing & Sponsoring</a></li>
<li><a title="Community support" href="http://lists.ninenines.eu">Mailing Lists</a></li>
<li><a title="Contact us" href="mailto:[email protected]">Contact</a></li>
</ul>
</nav>
<ul id="social">
<li>
<a href="https://github.com/ninenines" title="Check our Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a>
</li>
<li class="dropdown" id="twitter-links">
<a href="#twitter-links" class="dropdown-toggle" data-toggle="dropdown" title="Follow us on Twitter">
<img src="/img/ico_twitter.png" data-hover="/img/ico_twitter_alt.png" alt="Twitter">
</a>
<ul class="dropdown-menu">
<li><a title="Visit Loïc Hoguin's Twitter Account" href="http://twitter.com/lhoguin">@lhoguin</a></li>
<!-- <li class="divider"></li>
<li><a title="Visit our official Twitter account" href="#">@99s</a></li> -->
</ul>
</li>
<!-- <li>
<a href="/css/" title="Add us on Linkedin"><img src="/img/ico_linkedin.png" data-hover="img/ico_linkedin_alt.png" alt="Linkedin"></a>
</li> -->
</ul>
</div>
</div>
</div>
</div>
</header>
<div id="contents" class="two_col">
<div class="container">
<div class="row">
<div id="docs" class="span9 maincol">
<h1 class="lined-header"><span>Reading the request body</span></h1>
<p>The Req object also allows you to read the request body.</p>
<p>Because the request body can be of any size, all body reading operations will only work once, as Cowboy will not cache the result of these operations.</p>
<p>Cowboy will not attempt to read the body until you do. If handler execution ends without reading it, Cowboy will simply skip it.</p>
<p>Cowboy provides different ways to read the request body. You can read it directly, stream it, but also read and parse in a single call for form urlencoded formats or multipart. All of these except multipart are covered in this chapter. Multipart is covered later on in the guide.</p>
<h2 id="check_for_request_body">Check for request body</h2>
<p>You can check whether a body was sent with the request.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
cowboy_req:has_body(Req).
]]></script>
<p>It will return <code>true</code> if there is a request body, and <code>false</code> otherwise.</p>
<p>Note that it is generally safe to assume that a body is sent for <code>POST</code>, <code>PUT</code> and <code>PATCH</code> requests, without having to explicitly check for it.</p>
<h2 id="request_body_length">Request body length</h2>
<p>You can obtain the body length if it was sent with the request.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{Length, Req2} = cowboy_req:body_length(Req).
]]></script>
<p>The value returned will be <code>undefined</code> if the length couldn't be figured out from the request headers. If there's a body but no length is given, this means that the chunked transfer-encoding was used. You can read chunked bodies by using the stream functions.</p>
<h2 id="reading_the_body">Reading the body</h2>
<p>You can read the whole body directly in one call.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, Body, Req2} = cowboy_req:body(Req).
]]></script>
<p>By default, Cowboy will attempt to read up to a size of 8MB. You can override this limit as needed.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, Body, Req2} = cowboy_req:body(Req, [{length, 100000000}]).
]]></script>
<p>You can also disable it.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, Body, Req2} = cowboy_req:body(Req, [{length, infinity}]).
]]></script>
<p>It is recommended that you do not disable it for public facing websites.</p>
<p>If the body is larger than the limit, then Cowboy will return a <code>more</code> tuple instead, allowing you to stream it if you would like to.</p>
<h2 id="streaming_the_body">Streaming the body</h2>
<p>You can stream the request body by chunks.</p>
<p>Cowboy returns a <code>more</code> tuple when there is more body to be read, and an <code>ok</code> tuple for the last chunk. This allows you to loop over all chunks.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
body_to_console(Req) ->
case cowboy_req:body(Req) of
{ok, Data, Req2} ->
io:format("~s", [Data]),
Req2;
{more, Data, Req2} ->
io:format("~s", [Data]),
body_to_console(Req2)
end.
]]></script>
<p>You can of course set the <code>length</code> option to configure the size of chunks.</p>
<h2 id="rate_of_data_transmission">Rate of data transmission</h2>
<p>You can control the rate of data transmission by setting options when calling body functions. This applies not only to the functions described in this chapter, but also to the multipart functions.</p>
<p>The <code>read_length</code> option defines the maximum amount of data to be received from the socket at once, in bytes.</p>
<p>The <code>read_timeout</code> option defines the time Cowboy waits before that amount is received, in milliseconds.</p>
<h2 id="transfer_and_content_decoding">Transfer and content decoding</h2>
<p>Cowboy will by default decode the chunked transfer-encoding if any. It will not decode any content-encoding by default.</p>
<p>The first time you call a body function you can set the <code>transfer_decode</code> and <code>content_decode</code> options. If the body was already started being read these options are simply ignored.</p>
<p>The following example shows how to set both options.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, Req2} = cowboy_req:body(Req, [
{transfer_decode, fun transfer_decode/2, TransferState},
{content_decode, fun content_decode/1}
]).
]]></script>
<h2 id="reading_a_form_urlencoded_body">Reading a form urlencoded body</h2>
<p>You can directly obtain a list of key/value pairs if the body was sent using the application/x-www-form-urlencoded content-type.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, KeyValues, Req2} = cowboy_req:body_qs(Req).
]]></script>
<p>You can then retrieve an individual value from that list.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{_, Lang} = lists:keyfind(lang, 1, KeyValues).
]]></script>
<p>You should not attempt to match on the list as the order of the values is undefined.</p>
<p>By default Cowboy will reject bodies with a size above 64KB when using this function. You can override this limit by setting the <code>length</code> option.</p>
<script type="syntaxhighlighter" class="brush: erlang"><![CDATA[
{ok, KeyValues, Req2} = cowboy_req:body_qs(Req,
[{length, 2000000}]).
]]></script>
<!-- a.code -->
</div>
<div class="span3 sidecol">
<div class="input-append">
<form id="form-search" class="form-search" action="#">
<input id="input-search" type="text" placeholder="Function search" autocomplete="off" autofocus class="input-medium search-query span2">
<button type="submit" class="btn btn-success">Go</button>
</form>
</div>
<h3 id="docs-nav">Navigation</h3>
<h3>See also</h3><ul><li><a href="/docs/en/cowboy/1.0/manual/">Function Reference</a></li><li><a href="/docs/en/cowboy/1.0/index.html">README</a></li></ul>
<h3>Version select</h3>
<ul>
<li><a href="/docs/en/cowboy/1.0/guide/"><strong>1.0</strong></a></li>
<li><a href="/docs/en/cowboy/HEAD/guide/"><strong>HEAD</strong></a></li>
</ul>
</div>
</div>
</div>
</div>
<footer>
<div class="container">
<div class="row">
<div class="span6">
<p id="scroll-top"><a href="#">↑ Scroll to top</a></p>
<nav>
<ul>
<li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li>
</ul>
</nav>
</div>
<div class="span6 credits">
<p><img src="/img/footer_logo.png"></p>
<p>Copyright © Nine Nines 2012-2014</p>
</div>
</div>
</div>
</footer>
<!-- Javascript -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script src="/js/bootstrap-carousel.js"></script>
<script src="/js/bootstrap-dropdown.js"></script>
<script src="/js/custom.js"></script>
<script type="text/javascript" src="/js/shCore.js"></script>
<script type="text/javascript" src="/js/shlang/shBrushBash.js"></script>
<script type="text/javascript" src="/js/shlang/shBrushErlang.js"></script>
<script type="text/javascript" src="/js/shlang/shBrushJScript.js"></script>
<script type="text/javascript" src="/js/shlang/shBrushPlain.js"></script>
<script type="text/javascript">SyntaxHighlighter.all();</script>
<script type="text/javascript" src="/js/fuse.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
var f;
$.getJSON("/docs/db.json", function(data){
f = new Fuse(data, {keys: ["n"], threshold: 0.3});
$("<ul id=\"search-results\">").insertAfter("#form-search");
});
$("#input-search").keyup(function(e){if(f){if (e.which != 13 ){
var results = f.search($(this).val());
if (results.length == 0){
$("#form-search").attr("action", "#");
}else{
$("#form-search").attr("action", results[0].l);
}
$("#search-results").empty();
for (var i = 0; i < 10 && i < results.length; i++){
$("<li><a href=\"" + results[i].l + "\">" + results[i].n + "</a></li>")
.appendTo("#search-results");
}
}}});
});
</script>
</body>
</html>
|
