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| author | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
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| committer | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
| commit | fe3492a98de29942477b061cd02c92246f4bf85a (patch) | |
| tree | 2255b796a657e6e4dfb72beec1141258d17f1220 /docs/en/cowboy/2.0/guide/handlers | |
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Initial commit, new website system
Diffstat (limited to 'docs/en/cowboy/2.0/guide/handlers')
| -rw-r--r-- | docs/en/cowboy/2.0/guide/handlers/index.html | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/docs/en/cowboy/2.0/guide/handlers/index.html b/docs/en/cowboy/2.0/guide/handlers/index.html new file mode 100644 index 00000000..4d42be27 --- /dev/null +++ b/docs/en/cowboy/2.0/guide/handlers/index.html @@ -0,0 +1,242 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Handlers</title> + + <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 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"> + + +</head> + + +<body class=""> + <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"> + + <div id="side-header"> + <nav> + <ul> + <li><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li class="active"><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></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>Handlers</span></h1> + +<div class="paragraph"><p>Handlers are Erlang modules that handle HTTP requests.</p></div>
+<div class="sect1">
+<h2 id="_plain_http_handlers">Plain HTTP handlers</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The most basic handler in Cowboy implements the mandatory
+<code>init/2</code> callback, manipulates the request, optionally
+sends a response and then returns.</p></div>
+<div class="paragraph"><p>This callback receives the <a href="../req">Req object</a> and the options
+defined during the <a href="../routing">router configuration</a>.</p></div>
+<div class="paragraph"><p>A handler that does nothing would look like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">_Opts</span>) <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #008080">#state</span>{}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Despite sending no reply, a <code>204 No Content</code> reply will be
+sent to the client, as Cowboy makes sure that a reply is
+sent for every request.</p></div>
+<div class="paragraph"><p>We need to use the Req object for sending a reply.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">_Opts</span>) <span style="color: #990000">-></span>
+ <span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, [
+ {<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/plain"</span><span style="color: #990000">>></span>}
+ ], <span style="color: #990000"><<</span><span style="color: #FF0000">"Hello World!"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req2</span>, <span style="color: #008080">#state</span>{}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>As you can see we return a 3-tuple. <code>ok</code> means that the
+handler ran successfully. The Req object is returned as
+it may have been modified as is the case here: replying
+returns a modified Req object that you need to return
+back to Cowboy for proper operations.</p></div>
+<div class="paragraph"><p>The last value of the tuple is a state that will be used
+in every subsequent callbacks to this handler. Plain HTTP
+handlers only have one additional callback, the optional
+<code>terminate/3</code>.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_other_handlers">Other handlers</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The <code>init/2</code> callback can also be used to inform Cowboy
+that this is a different kind of handler and that Cowboy
+should switch to it. To do this you simply need to return
+the module name of the handler type you want to switch to.</p></div>
+<div class="paragraph"><p>Cowboy comes with three handler types you can switch to:
+<a href="../rest_handlers">cowboy_rest</a>, <a href="#ws_handlers">cowboy_websocket</a>
+and <a href="../loop_handlers">cowboy_loop</a>. In addition to those you
+can define your own handler types.</p></div>
+<div class="paragraph"><p>Switching is simple. Instead of returning <code>ok</code>, you simply
+return the name of the handler type you want to use. The
+following snippet switches to a Websocket handler:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">_Opts</span>) <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">cowboy_websocket</span>, <span style="color: #009900">Req</span>, <span style="color: #008080">#state</span>{}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You can also switch to your own custom handler type:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">_Opts</span>) <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">my_handler_type</span>, <span style="color: #009900">Req</span>, <span style="color: #008080">#state</span>{}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>How to implement a custom handler type is described in the
+<a href="../sub_protocols">Sub protocols</a> chapter.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_cleaning_up">Cleaning up</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>All handlers coming with Cowboy allow the use of the optional
+<code>terminate/3</code> callback.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">terminate</span></span>(<span style="color: #009900">_Reason</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span>
+ <span style="color: #FF6600">ok</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>This callback is strictly reserved for any required cleanup.
+You cannot send a response from this function. There is no
+other return value.</p></div>
+<div class="paragraph"><p>If you used the process dictionary, timers, monitors or may
+be receiving messages, then you can use this function to clean
+them up, as Cowboy might reuse the process for the next
+keep-alive request.</p></div>
+<div class="paragraph"><p>Note that while this function may be called in a Websocket
+handler, it is generally not useful to do any clean up as
+the process terminates immediately after calling this callback
+when using Websocket.</p></div>
+</div>
+</div>
+ + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.0 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <li><a href="/docs/en/cowboy/1.0/guide">1.0</a></li> + + <li><a href="/docs/en/cowboy/2.0/guide">2.0</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 © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <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> + </body> +</html> + + |