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1 files changed, 405 insertions, 402 deletions
diff --git a/docs/en/cowboy/2.0/guide/req/index.html b/docs/en/cowboy/2.0/guide/req/index.html index 6ff5b0a7..bdf6b6b9 100644 --- a/docs/en/cowboy/2.0/guide/req/index.html +++ b/docs/en/cowboy/2.0/guide/req/index.html @@ -7,7 +7,7 @@ <meta name="description" content=""> <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> - <meta name="generator" content="Hugo 0.17" /> + <meta name="generator" content="Hugo 0.26" /> <title>Nine Nines: The Req object</title> @@ -67,413 +67,416 @@ <h1 class="lined-header"><span>The Req object</span></h1> -<div class="paragraph"><p>The Req object is a variable used for obtaining information
-about a request, read its body or send a response.</p></div>
-<div class="paragraph"><p>It is not really an object in the object-oriented sense.
-It is a simple map that can be directly accessed or
-used when calling functions from the <code>cowboy_req</code> module.</p></div>
-<div class="paragraph"><p>The Req object is the subject of a few different chapters.
-In this chapter we will learn about the Req object and
-look at how to retrieve information about the request.</p></div>
-<div class="sect1">
-<h2 id="_direct_access">Direct access</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The Req map contains a number of fields which are documented
-and can be accessed directly. They are the fields that have
-a direct mapping to HTTP: the request <code>method</code>; the HTTP
-<code>version</code> used; the effective URI components <code>scheme</code>,
-<code>host</code>, <code>port</code>, <code>path</code> and <code>qs</code>; the request <code>headers</code>;
-and the connection <code>peer</code> address and port.</p></div>
-<div class="paragraph"><p>Note that the <code>version</code> field can be used to determine
-whether a connection is using HTTP/2.</p></div>
-<div class="paragraph"><p>To access a field, you can simply match in the function
-head. The following example sends a simple "Hello world!"
-response when the <code>method</code> is GET, and a 405 error
-otherwise.</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">Req0</span><span style="color: #990000">=</span>#{<span style="color: #FF6600">method</span> <span style="color: #990000">:=</span> <span style="color: #990000"><<</span><span style="color: #FF0000">"GET"</span><span style="color: #990000">>></span>}, <span style="color: #009900">State</span>) <span style="color: #990000">-></span>
- <span style="color: #009900">Req</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: #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">Req0</span>),
- {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>};
-<span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req0</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span>
- <span style="color: #009900">Req</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">405</span>, #{
- <span style="color: #990000"><<</span><span style="color: #FF0000">"allow"</span><span style="color: #990000">>></span> <span style="color: #990000">=></span> <span style="color: #990000"><<</span><span style="color: #FF0000">"GET"</span><span style="color: #990000">>></span>
- }, <span style="color: #009900">Req0</span>),
- {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Any other field is internal and should not be accessed.
-They may change in future releases, including maintenance
-releases, without notice.</p></div>
-<div class="paragraph"><p>Modifying the Req object, while allowed, is not recommended
-unless strictly necessary. If adding new fields, make sure
-to namespace the field names so that no conflict can occur
-with future Cowboy updates or third party projects.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_introduction_to_the_cowboy_req_interface">Introduction to the cowboy_req interface</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Functions in the <code>cowboy_req</code> module provide access to
-the request information but also various operations that
-are common when dealing with HTTP requests.</p></div>
-<div class="paragraph"><p>All the functions that begin with a verb indicate an action.
-Other functions simply return the corresponding value
-(sometimes that value does need to be built, but the
-cost of the operation is equivalent to retrieving a value).</p></div>
-<div class="paragraph"><p>Some of the <code>cowboy_req</code> functions return an updated Req
-object. They are the read, reply, set and delete functions.
-While ignoring the returned Req will not cause incorrect
-behavior for some of them, it is highly recommended to
-always keep and use the last returned Req object. The
-manual for <code>cowboy_req</code> details these functions and what
-modifications are done to the Req object.</p></div>
-<div class="paragraph"><p>Some of the calls to <code>cowboy_req</code> have side effects. This
-is the case of the read and reply functions. Cowboy reads
-the request body or replies immediately when the function
-is called.</p></div>
-<div class="paragraph"><p>All functions will crash if something goes wrong. There
-is usually no need to catch these errors, Cowboy will
-send the appropriate 4xx or 5xx response depending on
-where the crash occurred.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_request_method">Request method</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The request method can be retrieved directly:</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="color: #FF6600">method</span> <span style="color: #990000">:=</span> <span style="color: #009900">Method</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Or using a function:</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="color: #009900">Method</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:method</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>The method is a case sensitive binary string. Standard
-methods include GET, HEAD, OPTIONS, PATCH, POST, PUT
-or DELETE.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_http_version">HTTP version</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The HTTP version is informational. It does not indicate that
-the client implements the protocol well or fully.</p></div>
-<div class="paragraph"><p>There is typically no need to change behavior based on the
-HTTP version: Cowboy already does it for you.</p></div>
-<div class="paragraph"><p>It can be useful in some cases, though. For example, one may
-want to redirect HTTP/1.1 clients to use Websocket, while HTTP/2
-clients keep using HTTP/2.</p></div>
-<div class="paragraph"><p>The HTTP version can be retrieved directly:</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="color: #FF6600">version</span> <span style="color: #990000">:=</span> <span style="color: #009900">Version</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Or using a function:</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="color: #009900">Version</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:version</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Cowboy defines the <code>'HTTP/1.0'</code>, <code>'HTTP/1.1'</code> and <code>'HTTP/2'</code>
-versions. Custom protocols can define their own values as
-atoms.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_effective_request_uri">Effective request URI</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The scheme, host, port, path and query string components
-of the effective request URI can all be retrieved directly:</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="color: #FF6600">scheme</span> <span style="color: #990000">:=</span> <span style="color: #009900">Scheme</span>,
- <span style="color: #FF6600">host</span> <span style="color: #990000">:=</span> <span style="color: #009900">Host</span>,
- <span style="color: #FF6600">port</span> <span style="color: #990000">:=</span> <span style="color: #009900">Port</span>,
- <span style="color: #FF6600">path</span> <span style="color: #990000">:=</span> <span style="color: #009900">Path</span>,
- <span style="color: #FF6600">qs</span> <span style="color: #990000">:=</span> <span style="color: #009900">Qs</span>
-} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Or using the related functions:</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="color: #009900">Scheme</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:scheme</span></span>(<span style="color: #009900">Req</span>),
-<span style="color: #009900">Host</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:host</span></span>(<span style="color: #009900">Req</span>),
-<span style="color: #009900">Port</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:port</span></span>(<span style="color: #009900">Req</span>),
-<span style="color: #009900">Path</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:path</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span>
-<span style="color: #009900">Qs</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:qs</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>The scheme and host are lowercased case insensitive binary
-strings. The port is an integer representing the port number.
-The path and query string are case sensitive binary strings.</p></div>
-<div class="paragraph"><p>Cowboy defines only the <code><<"http">></code> and <code><<"https">></code> schemes.
-They are chosen so that the scheme will only be <code><<"https">></code>
-for requests on secure HTTP/1.1 or HTTP/2 connections.</p></div>
-<div class="paragraph"><p>The effective request URI itself can be reconstructed with
-the <code>cowboy_req:uri/1,2</code> function. By default, an absolute
-URI is returned:</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-style: italic"><span style="color: #9A1900">%% </span></span><span style="text-decoration: underline"><span style="color: #0000FF">scheme://host</span></span><span style="font-style: italic"><span style="color: #9A1900">[:port]/path[?qs]</span></span>
-<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Options are available to either disable or replace some
-or all of the components. Various URIs or URI formats can
-be generated this way, including the origin form:</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-style: italic"><span style="color: #9A1900">%% /path[?qs]</span></span>
-<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">host</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>The protocol relative form:</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-style: italic"><span style="color: #9A1900">%% //host[:port]/path[?qs]</span></span>
-<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">scheme</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>The absolute URI without a query string:</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="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">qs</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>A different host:</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="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">host</span> <span style="color: #990000">=></span> <span style="color: #990000"><<</span><span style="color: #FF0000">"example.org"</span><span style="color: #990000">>></span>})<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>And any other combination.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_bindings">Bindings</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Bindings are the host and path components that you chose
-to extract when defining the routes of your application.
-They are only available after the routing.</p></div>
-<div class="paragraph"><p>Cowboy provides functions to retrieve one or all bindings.</p></div>
-<div class="paragraph"><p>To retrieve a single value:</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="color: #009900">Value</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:binding</span></span>(<span style="color: #FF6600">userid</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>When attempting to retrieve a value that was not bound,
-<code>undefined</code> will be returned. A different default value
-can be provided:</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="color: #009900">Value</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:binding</span></span>(<span style="color: #FF6600">userid</span>, <span style="color: #009900">Req</span>, <span style="color: #993399">42</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>To retrieve everything that was bound:</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="color: #009900">Bindings</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:bindings</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>They are returned as a map, with keys being atoms.</p></div>
-<div class="paragraph"><p>The Cowboy router also allows you to capture many host
-or path segments at once using the <code>...</code> qualifier.</p></div>
-<div class="paragraph"><p>To retrieve the segments captured from the host name:</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="color: #009900">HostInfo</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:host_info</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>And the path segments:</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="color: #009900">PathInfo</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:path_info</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Cowboy will return <code>undefined</code> if <code>...</code> was not used
-in the route.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_query_parameters">Query parameters</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Cowboy provides two functions to access query parameters.
-You can use the first to get the entire list of parameters.</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="color: #009900">QsVals</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_qs</span></span>(<span style="color: #009900">Req</span>),
-{<span style="color: #990000">_</span>, <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">lists:keyfind</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"lang"</span><span style="color: #990000">>></span>, <span style="color: #993399">1</span>, <span style="color: #009900">QsVals</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Cowboy will only parse the query string, and not do any
-transformation. This function may therefore return duplicates,
-or parameter names without an associated value. The order of
-the list returned is undefined.</p></div>
-<div class="paragraph"><p>When a query string is <code>key=1&key=2</code>, the list returned will
-contain two parameters of name <code>key</code>.</p></div>
-<div class="paragraph"><p>The same is true when trying to use the PHP-style suffix <code>[]</code>.
-When a query string is <code>key[]=1&key[]=2</code>, the list returned will
-contain two parameters of name <code>key[]</code>.</p></div>
-<div class="paragraph"><p>When a query string is simply <code>key</code>, Cowboy will return the
-list <code>[{<<"key">>, true}]</code>, using <code>true</code> to indicate that the
-parameter <code>key</code> was defined, but with no value.</p></div>
-<div class="paragraph"><p>The second function Cowboy provides allows you to match out
-only the parameters you are interested in, and at the same
-time do any post processing you require using <a href="../constraints">constraints</a>.
-This function returns a map.</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="color: #FF6600">id</span> <span style="color: #990000">:=</span> <span style="color: #009900">ID</span>, <span style="color: #FF6600">lang</span> <span style="color: #990000">:=</span> <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([<span style="color: #FF6600">id</span>, <span style="color: #FF6600">lang</span>], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Constraints can be applied automatically. The following
-snippet will crash when the <code>id</code> parameter is not an integer,
-or when the <code>lang</code> parameter is empty. At the same time, the
-value for <code>id</code> will be converted to an integer term:</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="color: #009900">QsMap</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([{<span style="color: #FF6600">id</span>, <span style="color: #FF6600">int</span>}, {<span style="color: #FF6600">lang</span>, <span style="color: #FF6600">nonempty</span>}], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>A default value may also be provided. The default will be used
-if the <code>lang</code> key is not found. It will not be used if
-the key is found but has an empty value.</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="color: #FF6600">lang</span> <span style="color: #990000">:=</span> <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([{<span style="color: #FF6600">lang</span>, [], <span style="color: #990000"><<</span><span style="color: #FF0000">"en-US"</span><span style="color: #990000">>></span>}], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>If no default is provided and the value is missing, the
-query string is deemed invalid and the process will crash.</p></div>
-<div class="paragraph"><p>When the query string is <code>key=1&key=2</code>, the value for <code>key</code>
-will be the list <code>[1, 2]</code>. Parameter names do not need to
-include the PHP-style suffix. Constraints may be used to
-ensure that only one value was passed through.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_headers">Headers</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Header values can be retrieved either as a binary string
-or parsed into a more meaningful representation.</p></div>
-<div class="paragraph"><p>The get the raw value:</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="color: #009900">HeaderVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Cowboy expects all header names to be provided as lowercase
-binary strings. This is true for both requests and responses,
-regardless of the underlying protocol.</p></div>
-<div class="paragraph"><p>When the header is missing from the request, <code>undefined</code>
-will be returned. A different default can be provided:</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="color: #009900">HeaderVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/plain"</span><span style="color: #990000">>></span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>All headers can be retrieved at once, either directly:</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="color: #FF6600">headers</span> <span style="color: #990000">:=</span> <span style="color: #009900">AllHeaders</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Or using a function:</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="color: #009900">AllHeaders</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:headers</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Cowboy provides equivalent functions to parse individual
-headers. There is no function to parse all headers at once.</p></div>
-<div class="paragraph"><p>To parse a specific header:</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="color: #009900">ParsedVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>An exception will be thrown if it doesn’t know how to parse the
-given header, or if the value is invalid. The list of known headers
-and default values can be found in the manual.</p></div>
-<div class="paragraph"><p>When the header is missing, <code>undefined</code> is returned. You can
-change the default value. Note that it should be the parsed value
-directly:</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="color: #009900">ParsedVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>,
- {<span style="color: #990000"><<</span><span style="color: #FF0000">"text"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"plain"</span><span style="color: #990000">>></span>, []})<span style="color: #990000">.</span></tt></pre></div></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_peer">Peer</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The peer address and port number for the connection can be
-retrieved either directly or using a function.</p></div>
-<div class="paragraph"><p>To retrieve the peer directly:</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="color: #FF6600">peer</span> <span style="color: #990000">:=</span> {<span style="color: #009900">IP</span>, <span style="color: #009900">Port</span>}} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>And using a function:</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="color: #009900">IP</span>, <span style="color: #009900">Port</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:peer</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Note that the peer corresponds to the remote end of the
-connection to the server, which may or may not be the
-client itself. It may also be a proxy or a gateway.</p></div>
-</div>
-</div>
+<div class="paragraph"><p>The Req object is a variable used for obtaining information +about a request, read its body or send a response.</p></div> +<div class="paragraph"><p>It is not really an object in the object-oriented sense. +It is a simple map that can be directly accessed or +used when calling functions from the <code>cowboy_req</code> module.</p></div> +<div class="paragraph"><p>The Req object is the subject of a few different chapters. +In this chapter we will learn about the Req object and +look at how to retrieve information about the request.</p></div> +<div class="sect1"> +<h2 id="_direct_access">Direct access</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The Req map contains a number of fields which are documented +and can be accessed directly. They are the fields that have +a direct mapping to HTTP: the request <code>method</code>; the HTTP +<code>version</code> used; the effective URI components <code>scheme</code>, +<code>host</code>, <code>port</code>, <code>path</code> and <code>qs</code>; the request <code>headers</code>; +and the connection <code>peer</code> address and port.</p></div> +<div class="paragraph"><p>Note that the <code>version</code> field can be used to determine +whether a connection is using HTTP/2.</p></div> +<div class="paragraph"><p>To access a field, you can simply match in the function +head. The following example sends a simple "Hello world!" +response when the <code>method</code> is GET, and a 405 error +otherwise.</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">Req0</span><span style="color: #990000">=</span>#{<span style="color: #FF6600">method</span> <span style="color: #990000">:=</span> <span style="color: #990000"><<</span><span style="color: #FF0000">"GET"</span><span style="color: #990000">>></span>}, <span style="color: #009900">State</span>) <span style="color: #990000">-></span> + <span style="color: #009900">Req</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: #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">Req0</span>), + {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}; +<span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">Req0</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span> + <span style="color: #009900">Req</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">405</span>, #{ + <span style="color: #990000"><<</span><span style="color: #FF0000">"allow"</span><span style="color: #990000">>></span> <span style="color: #990000">=></span> <span style="color: #990000"><<</span><span style="color: #FF0000">"GET"</span><span style="color: #990000">>></span> + }, <span style="color: #009900">Req0</span>), + {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Any other field is internal and should not be accessed. +They may change in future releases, including maintenance +releases, without notice.</p></div> +<div class="paragraph"><p>Modifying the Req object, while allowed, is not recommended +unless strictly necessary. If adding new fields, make sure +to namespace the field names so that no conflict can occur +with future Cowboy updates or third party projects.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_introduction_to_the_cowboy_req_interface">Introduction to the cowboy_req interface</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Functions in the <code>cowboy_req</code> module provide access to +the request information but also various operations that +are common when dealing with HTTP requests.</p></div> +<div class="paragraph"><p>All the functions that begin with a verb indicate an action. +Other functions simply return the corresponding value +(sometimes that value does need to be built, but the +cost of the operation is equivalent to retrieving a value).</p></div> +<div class="paragraph"><p>Some of the <code>cowboy_req</code> functions return an updated Req +object. They are the read, reply, set and delete functions. +While ignoring the returned Req will not cause incorrect +behavior for some of them, it is highly recommended to +always keep and use the last returned Req object. The +manual for <code>cowboy_req</code> details these functions and what +modifications are done to the Req object.</p></div> +<div class="paragraph"><p>Some of the calls to <code>cowboy_req</code> have side effects. This +is the case of the read and reply functions. Cowboy reads +the request body or replies immediately when the function +is called.</p></div> +<div class="paragraph"><p>All functions will crash if something goes wrong. There +is usually no need to catch these errors, Cowboy will +send the appropriate 4xx or 5xx response depending on +where the crash occurred.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_request_method">Request method</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The request method can be retrieved directly:</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="color: #FF6600">method</span> <span style="color: #990000">:=</span> <span style="color: #009900">Method</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Or using a function:</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="color: #009900">Method</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:method</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>The method is a case sensitive binary string. Standard +methods include GET, HEAD, OPTIONS, PATCH, POST, PUT +or DELETE.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_http_version">HTTP version</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The HTTP version is informational. It does not indicate that +the client implements the protocol well or fully.</p></div> +<div class="paragraph"><p>There is typically no need to change behavior based on the +HTTP version: Cowboy already does it for you.</p></div> +<div class="paragraph"><p>It can be useful in some cases, though. For example, one may +want to redirect HTTP/1.1 clients to use Websocket, while HTTP/2 +clients keep using HTTP/2.</p></div> +<div class="paragraph"><p>The HTTP version can be retrieved directly:</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="color: #FF6600">version</span> <span style="color: #990000">:=</span> <span style="color: #009900">Version</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Or using a function:</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="color: #009900">Version</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:version</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Cowboy defines the <code>'HTTP/1.0'</code>, <code>'HTTP/1.1'</code> and <code>'HTTP/2'</code> +versions. Custom protocols can define their own values as +atoms.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_effective_request_uri">Effective request URI</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The scheme, host, port, path and query string components +of the effective request URI can all be retrieved directly:</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="color: #FF6600">scheme</span> <span style="color: #990000">:=</span> <span style="color: #009900">Scheme</span>, + <span style="color: #FF6600">host</span> <span style="color: #990000">:=</span> <span style="color: #009900">Host</span>, + <span style="color: #FF6600">port</span> <span style="color: #990000">:=</span> <span style="color: #009900">Port</span>, + <span style="color: #FF6600">path</span> <span style="color: #990000">:=</span> <span style="color: #009900">Path</span>, + <span style="color: #FF6600">qs</span> <span style="color: #990000">:=</span> <span style="color: #009900">Qs</span> +} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Or using the related functions:</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="color: #009900">Scheme</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:scheme</span></span>(<span style="color: #009900">Req</span>), +<span style="color: #009900">Host</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:host</span></span>(<span style="color: #009900">Req</span>), +<span style="color: #009900">Port</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:port</span></span>(<span style="color: #009900">Req</span>), +<span style="color: #009900">Path</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:path</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span> +<span style="color: #009900">Qs</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:qs</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>The scheme and host are lowercased case insensitive binary +strings. The port is an integer representing the port number. +The path and query string are case sensitive binary strings.</p></div> +<div class="paragraph"><p>Cowboy defines only the <code><<"http">></code> and <code><<"https">></code> schemes. +They are chosen so that the scheme will only be <code><<"https">></code> +for requests on secure HTTP/1.1 or HTTP/2 connections.</p></div> +<div class="paragraph"><p>The effective request URI itself can be reconstructed with +the <code>cowboy_req:uri/1,2</code> function. By default, an absolute +URI is returned:</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-style: italic"><span style="color: #9A1900">%% </span></span><span style="text-decoration: underline"><span style="color: #0000FF">scheme://host</span></span><span style="font-style: italic"><span style="color: #9A1900">[:port]/path[?qs]</span></span> +<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Options are available to either disable or replace some +or all of the components. Various URIs or URI formats can +be generated this way, including the origin form:</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-style: italic"><span style="color: #9A1900">%% /path[?qs]</span></span> +<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">host</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>The protocol relative form:</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-style: italic"><span style="color: #9A1900">%% //host[:port]/path[?qs]</span></span> +<span style="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">scheme</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>The absolute URI without a query string:</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="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">qs</span> <span style="color: #990000">=></span> <span style="color: #000080">undefined</span>})<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>A different host:</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="color: #009900">URI</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:uri</span></span>(<span style="color: #009900">Req</span>, #{<span style="color: #0000FF">host</span> <span style="color: #990000">=></span> <span style="color: #990000"><<</span><span style="color: #FF0000">"example.org"</span><span style="color: #990000">>></span>})<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>And any other combination.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_bindings">Bindings</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Bindings are the host and path components that you chose +to extract when defining the routes of your application. +They are only available after the routing.</p></div> +<div class="paragraph"><p>Cowboy provides functions to retrieve one or all bindings.</p></div> +<div class="paragraph"><p>To retrieve a single value:</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="color: #009900">Value</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:binding</span></span>(<span style="color: #FF6600">userid</span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>When attempting to retrieve a value that was not bound, +<code>undefined</code> will be returned. A different default value +can be provided:</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="color: #009900">Value</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:binding</span></span>(<span style="color: #FF6600">userid</span>, <span style="color: #009900">Req</span>, <span style="color: #993399">42</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>To retrieve everything that was bound:</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="color: #009900">Bindings</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:bindings</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>They are returned as a map, with keys being atoms.</p></div> +<div class="paragraph"><p>The Cowboy router also allows you to capture many host +or path segments at once using the <code>...</code> qualifier.</p></div> +<div class="paragraph"><p>To retrieve the segments captured from the host name:</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="color: #009900">HostInfo</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:host_info</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>And the path segments:</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="color: #009900">PathInfo</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:path_info</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Cowboy will return <code>undefined</code> if <code>...</code> was not used +in the route.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_query_parameters">Query parameters</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Cowboy provides two functions to access query parameters. +You can use the first to get the entire list of parameters.</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="color: #009900">QsVals</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_qs</span></span>(<span style="color: #009900">Req</span>), +{<span style="color: #990000">_</span>, <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">lists:keyfind</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"lang"</span><span style="color: #990000">>></span>, <span style="color: #993399">1</span>, <span style="color: #009900">QsVals</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Cowboy will only parse the query string, and not do any +transformation. This function may therefore return duplicates, +or parameter names without an associated value. The order of +the list returned is undefined.</p></div> +<div class="paragraph"><p>When a query string is <code>key=1&key=2</code>, the list returned will +contain two parameters of name <code>key</code>.</p></div> +<div class="paragraph"><p>The same is true when trying to use the PHP-style suffix <code>[]</code>. +When a query string is <code>key[]=1&key[]=2</code>, the list returned will +contain two parameters of name <code>key[]</code>.</p></div> +<div class="paragraph"><p>When a query string is simply <code>key</code>, Cowboy will return the +list <code>[{<<"key">>, true}]</code>, using <code>true</code> to indicate that the +parameter <code>key</code> was defined, but with no value.</p></div> +<div class="paragraph"><p>The second function Cowboy provides allows you to match out +only the parameters you are interested in, and at the same +time do any post processing you require using <a href="../constraints">constraints</a>. +This function returns a map.</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="color: #FF6600">id</span> <span style="color: #990000">:=</span> <span style="color: #009900">ID</span>, <span style="color: #FF6600">lang</span> <span style="color: #990000">:=</span> <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([<span style="color: #FF6600">id</span>, <span style="color: #FF6600">lang</span>], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Constraints can be applied automatically. The following +snippet will crash when the <code>id</code> parameter is not an integer, +or when the <code>lang</code> parameter is empty. At the same time, the +value for <code>id</code> will be converted to an integer term:</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="color: #009900">QsMap</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([{<span style="color: #FF6600">id</span>, <span style="color: #FF6600">int</span>}, {<span style="color: #FF6600">lang</span>, <span style="color: #FF6600">nonempty</span>}], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>A default value may also be provided. The default will be used +if the <code>lang</code> key is not found. It will not be used if +the key is found but has an empty value.</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="color: #FF6600">lang</span> <span style="color: #990000">:=</span> <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>([{<span style="color: #FF6600">lang</span>, [], <span style="color: #990000"><<</span><span style="color: #FF0000">"en-US"</span><span style="color: #990000">>></span>}], <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>If no default is provided and the value is missing, the +query string is deemed invalid and the process will crash.</p></div> +<div class="paragraph"><p>When the query string is <code>key=1&key=2</code>, the value for <code>key</code> +will be the list <code>[1, 2]</code>. Parameter names do not need to +include the PHP-style suffix. Constraints may be used to +ensure that only one value was passed through.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_headers">Headers</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Header values can be retrieved either as a binary string +or parsed into a more meaningful representation.</p></div> +<div class="paragraph"><p>The get the raw value:</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="color: #009900">HeaderVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Cowboy expects all header names to be provided as lowercase +binary strings. This is true for both requests and responses, +regardless of the underlying protocol.</p></div> +<div class="paragraph"><p>When the header is missing from the request, <code>undefined</code> +will be returned. A different default can be provided:</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="color: #009900">HeaderVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"text/plain"</span><span style="color: #990000">>></span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>All headers can be retrieved at once, either directly:</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="color: #FF6600">headers</span> <span style="color: #990000">:=</span> <span style="color: #009900">AllHeaders</span>} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Or using a function:</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="color: #009900">AllHeaders</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:headers</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Cowboy provides equivalent functions to parse individual +headers. There is no function to parse all headers at once.</p></div> +<div class="paragraph"><p>To parse a specific header:</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="color: #009900">ParsedVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>An exception will be thrown if it doesn’t know how to parse the +given header, or if the value is invalid. The list of known headers +and default values can be found in the manual.</p></div> +<div class="paragraph"><p>When the header is missing, <code>undefined</code> is returned. You can +change the default value. Note that it should be the parsed value +directly:</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="color: #009900">ParsedVal</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>, + {<span style="color: #990000"><<</span><span style="color: #FF0000">"text"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"plain"</span><span style="color: #990000">>></span>, []})<span style="color: #990000">.</span></tt></pre></div></div> +</div> +</div> +<div class="sect1"> +<h2 id="_peer">Peer</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The peer address and port number for the connection can be +retrieved either directly or using a function.</p></div> +<div class="paragraph"><p>To retrieve the peer directly:</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="color: #FF6600">peer</span> <span style="color: #990000">:=</span> {<span style="color: #009900">IP</span>, <span style="color: #009900">Port</span>}} <span style="color: #990000">=</span> <span style="color: #009900">Req</span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>And using a function:</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="color: #009900">IP</span>, <span style="color: #009900">Port</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:peer</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Note that the peer corresponds to the remote end of the +connection to the server, which may or may not be the +client itself. It may also be a proxy or a gateway.</p></div> +</div> +</div> + + + <nav style="margin:1em 0"> |