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<!DOCTYPE html>
<html prefix="dc: http://purl.org/dc/elements/1.1/" lang="en">
<head>
<title>Liberator</title>
<meta charset="utf-8">
<meta property="dc:creator" content="Malcolm Sparks"/>
<meta property="dc:contributor" content="Philipp Meier"/>
<meta property="dc:language" content="en"/>
<meta property="dc:title" content="Liberator"/>
<meta property="dc:description" content="A free, open-source web library for the Clojure programming language with an emphasis on REST"/>
<!-- http://www.google.com/webfonts#UsePlace:use/Collection:Molengo|Anonymous+Pro:400,700|Oregano -->
<link href='http://fonts.googleapis.com/css?family=Molengo|Anonymous+Pro:400,700|Oregano' rel='stylesheet' type='text/css'>
<style>
html {
margin: 0;
padding: 0;
}
body {
margin: 0;
padding: 0;
color: black;
font-family: Molengo,Helvetica,Arial;
font-size: 11pt;
background: #cfcfcf;
background-image: url("zenbg-1.png"), url("zenbg-2.png");
background-repeat: repeat-x, repeat;
}
#title { display: none; }
div.fixed {
position: fixed;
}
div#logo {
float: left;
width: 70px;
margin-top: 10px;
margin-left: 10px;
border: 1px solid black;
}
<!--
We have a fixed header of 40px, we means that the anchor links need to be offset by the same.
http://www.pixelflips.com/blog/anchor-links-with-a-fixed-header/
-->
span.anchor {
display: block;
height: 40px;
margin-top: -40px;
display: hidden;
}
nav {
clear: left;
}
nav ul {
font-family: Molengo,Helvetica,Arial;
margin: 0 4pt;
padding: 0 0;
font-size: 12pt;
}
nav li {
list-style-type: none;
margin: 1em 0 1em 0;
padding: 2pt;
text-align: center;
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color: #363;
text-decoration: none;
}
nav li a:hover {
text-decoration: underline;
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font-size: 160%;
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padding-bottom: 40px;
margin-top: 50px;
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float: left;
box-shadow: -4px 4px 7px #aa8;
}
section {
width: 620px;
margin-left: 12pt;
margin-right: 12pt;
}
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margin: 4em 0 0 0;
float: left;
width: 320px;
}
aside {
background: #6c6;
margin: 10pt 0 30pt 10px;
font-size: 80%;
padding: 6pt 10pt 10pt 10pt;
box-shadow: 6px 6px 17px #aa8;
text-align: justify;
}
aside h1, aside h2 {
text-shadow: 1px 1px 6px #4a4;
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aside h2 { font-size: 14pt; }
svg { border: 0px dotted black }
div#logo svg { border: none; }
div#status { margin-left: 40pt; float: left }
dl.callouts dt { float: left; }
dl.callouts dd { font-size: 80%; padding-bottom: 4pt; margin-left: 16pt }
pre {
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figcaption {
margin: 4pt;
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</style>
</head>
<body>
<script>
show_alert = function() {
document.querySelector("#alert").classList.remove("hidden");
}
hide_alert = function() {
document.querySelector("#alert").classList.add("hidden");
}
</script>
<div id=banner class=fixed>
<h1>Liberator</h1>
</div>
<div id="alert" class=hidden>
<p>Just to let you know, this is an <span style="color: red; font-style: italic">unofficial</span> version of the Liberator site. The official version is
at <a href="http://clojure-liberator.github.com/">http://clojure-liberator.github.com/</a>. </p>
<p style="font-size: smaller"><a href="javascript:hide_alert()">Hide</a></p>
</div>
<script>
if (location.hostname != "clojure-liberator.github.com") {
show_alert();
}
</script>
<a href="https://github.com/clojure-liberator/liberator">
<img style="position: absolute; top: 0; right: 0; border: 0;" src="forkme_right_green_007200.png" alt="Fork me on GitHub">
</a>
<div class=fixed>
<nav>
<ul>
<li><a href="#introduction">Intro</a>
<li><a href="#flowchart">Flowchart</a>
<li><a href="#functions">Functions</a>
<li><a href="#getting-started">Get started</a>
<li><a href="#community">Community</a>
<li><a href="#faq">FAQ</a>
<li><a href="https://github.com/clojure-liberator/liberator">Github</a>
</ul>
</nav>
</div>
<div id=main>
<div id=content>
<!-- We put empty spans before each section to provide anchor targets:
See http://www.pixelflips.com/blog/anchor-links-with-a-fixed-header/ for more details. -->
<span class="anchor" id="introduction"></span>
<section>
<h1 id=title>Liberator</h1>
<p id=description>With Liberator it is <em>easy</em> to create <abbr title="Representational State Transfer">REST</abbr>ful web services in Clojure.</p>
</section>
<section>
<h2>What it is</h2>
<p>
Liberator is a Clojure library that helps you expose your data
as REST resources while automatically complying with all the
relevant requirements of HTTP specification
(<a href="http://www.ietf.org/rfc/rfc2616.txt">RFC-2616</a>). Your
resources will automatically gain useful HTTP features, such as
caching and content negotiation. Liberator is loosely modeled on
<a href="http://wiki.basho.com/Webmachine.html">webmachine</a>.
</section>
<span class="anchor" id="status"></span>
<section>
<h2>Status</h2>
<p>Latest version: <a href="https://clojars.org/liberator">0.5.0</a>
</section>
<section>
<h2>Where it fits</h2>
<p>
Liberator is not a full-featured web framework like
<a href="http://www.webnoir.org">Noir</a>. Rather, Liberator forms part of a composition of other components. So be prepared to ...
<ul>
<li>Add a routing library, like <a href="https://github.com/weavejester/compojure">Compojure</a> or <a href="https://github.com/cgrand/moustache">Moustache</a>
<li>Add a presentation library, like <a href="https://github.com/weavejester/hiccup">Hiccup</a>
<li>Add some miscellaneous Ring middleware
</ul>
<p>If you are familiar with Ring, Liberator <dfn>resources</dfn>
are Ring handlers. A Ring handler is a Clojure function that
takes a map as an argument (representing the web request) and
returns another map representing the web response.
<p>You connect a Liberator resource to a route. For example,
if you use Compojure as your routing library, you would connect things like this :-
<pre><code>(<span class="clojure symbol">ns</span> <span class="clojure symbol">com.acme</span>
(<span class="clojure keyword">:use</span>
[<span class="clojure symbol">compojure.core</span> <span class="clojure keyword">:only</span> [<span class="clojure symbol">ANY</span>]]
[<span class="clojure symbol">liberator.core</span> <span class="clojure keyword">:only</span> [<span class="clojure symbol">resource</span>]]))
(<span class="clojure symbol">ANY</span> <span class="clojure string">"/products/:sku"</span> [sku]
<span class="code highlight">(<span class="clojure symbol">resource</span> ①)</span></code></pre>
<dl class="callouts">
<dt>①
<dd>The Liberator <code>resource</code> function takes an
even number of arguments, each pair is a keyword
(indicating the argument name) and the argument
value. There are over 50 different arguments you can give
to this function, all of which will be explained
later.
</dl>
<p>Now if we sent a web request to the server with the path <code>/products/54354</code> it would be routed to our Liberator resource.
<p>This is how it all fits together :-
<figure>
<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" version="1.1" width="600" height="180">
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<style type="text/css">
<![CDATA[
text {
font-size: 9pt;
font-family: Molengo,Arial;
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<marker id="arrowhead"
viewBox="0 0 10 10" refX="5" refY="5"
markerUnits="strokeWidth"
markerWidth="4" markerHeight="3" fill="darkred"
stroke="black"
orient="auto">
<path d="M 0 0 L 10 5 L 0 10 z" />
</marker>
<linearGradient id="clojure">
<stop offset="5%" stop-color="#0f0" />
<stop offset="95%" stop-color="#0f0" />
</linearGradient>
<linearGradient id="liberator">
<stop offset="5%" stop-color="#FA0" />
<stop offset="95%" stop-color="#FA0" />
</linearGradient>
</defs>
<g transform="translate(30,20)">
<rect x="0" y="0" width="120" height="140" fill="grey" opacity="0.5" stroke="black" stroke-width="2"/>
<text x="60" y="60" text-anchor="middle" dominant-baseline="central">Browser or other</text>
<text x="60" y="80" text-anchor="middle" dominant-baseline="central">HTTP user-agent</text>
</g>
<g transform="translate(275,20)">
<rect x="0" y="0" width="100" height="140" fill="#0f0" opacity="0.5" stroke="black" stroke-width="2"/>
<text x="50" y="50" text-anchor="middle" dominant-baseline="central">Java-based</text>
<text x="50" y="70" text-anchor="middle" dominant-baseline="central">web server</text>
<text x="50" y="90" text-anchor="middle" dominant-baseline="central">(eg. Jetty)</text>
</g>
<a xlink:href="http://google.com?q=clojure+ring">
<g transform="translate(375,160) rotate(-90)">
<rect x="0" y="0" width="140" height="30" fill="url(#clojure)" opacity="0.5" stroke="black" stroke-width="2"/>
<text x="70" y="15" text-decoration="underline" text-anchor="middle" dominant-baseline="central" fill="blue">Ring interface</text>
</g>
</a>
<g transform="translate(405,160) rotate(-90)">
<rect x="0" y="0" width="140" height="40" fill="url(#clojure)" opacity="0.5" stroke="black" stroke-width="2"/>
<text x="70" y="12" text-anchor="middle" dominant-baseline="central">Ring-middleware</text>
<text x="70" y="28" text-anchor="middle" dominant-baseline="central">and routing</text>
</g>
<g transform="translate(450,160) rotate(-90)">
<!-- <rect x="0" y="0" width="140" height="55" fill="green" opacity="0.2" stroke="black" stroke-width="2"/> -->
<path d="M0,50 h20 v10 h20 v-10 h20 v10 h20 v-10 h20 v10 h20 v-10 h20 v-55 h-140 z" stroke-width="2" stroke="black" fill="url(#liberator)" opacity="0.5"/>
<text x="70" y="20"><tspan text-anchor="middle" dominant-baseline="central" font-size="12pt" font-weight="bold">Liberator</tspan></text>
</g>
<g transform="translate(515,160) rotate(-90)">
<!-- <rect x="0" y="0" width="140" height="40" fill="green" opacity="0.2" stroke="black" stroke-width="2"/>-->
<path d="M0,65 v-80 h20 v10 h20 v-10 h20 v10 h20 v-10 h20 v10 h20 v-10 h20 v80z" stroke-width="2" stroke="black" fill="url(#clojure)" opacity="0.5"/>
<text x="70" y="10"><tspan text-anchor="middle" dominant-baseline="central" font-size="12pt" font-weight="bold" fill="green">Your</tspan></text>
<text x="70" y="30"><tspan text-anchor="middle" dominant-baseline="central" font-size="12pt" font-weight="bold" fill="green">Clojure code</tspan></text>
</g>
<path id="request-response" d="M150,30 h400 a 60,20 270 0,1 0,120 h-390" stroke="darkred" opacity="0.5" stroke-width="5px" fill="none" marker-end="url(#arrowhead)"/>
<circle cx="0" cy="0" r="4" fill="white">
<desc>This is the 'pulse' that follows the request-response path to indicate the order that events happen. Not that useful but makes things a bit more obvious.</desc>
<animateMotion dur="2s" repeatCount="2" rotate="auto">
<mpath xlink:href="#request-response"/>
</animateMotion>
</circle>
</svg>
</figure>
<p>(If you need more information about adding the web server component, see the Ring documentation <a href="#">here</a>).
</section>
<span class="anchor" id="works"></span>
<section>
<h2>How it works</h2>
<p>Liberator works by using a <b>decision tree</b> to determine how to
properly handle the request.
<p>Every decision is made by a <dfn>decision function</dfn>. The
diagram below illustrates how the outcomes of decision functions
determine the response status and the <dfn>handler function</dfn>
that will produce the response.
<figure>
<svg id="flow-diagram" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" version="1.1" width="600" height="330">
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<tspan text-anchor="end" dominant-baseline="central"
font-style="normal">:service-available?</tspan>
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<text x="5" y="0"><tspan font-style="normal" dominant-baseline="middle" text-anchor="start">:handle-unauthorized</tspan></text>
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<text x="5" y="30" dominant-baseline="central" font-style="normal">:message</text>
<text x="75" y="30" dominant-baseline="central">"Not authorized."</text>
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<text x="-25" y="0" text-anchor="end" font-style="normal" dominant-baseline="central">:valid-entity-length?</text>
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<g transform="translate(40,0)">
<text x="5" y="0"><tspan font-style="normal" dominant-baseline="middle" text-anchor="start">:handle-request-entity-too-large</tspan></text>
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<text x="5" y="10" dominant-baseline="central" font-style="normal">:status</text>
<text x="75" y="10" dominant-baseline="central">413</text>
<use x="0" y="20" xlink:href="#entry"/>
<text x="5" y="30" dominant-baseline="central" font-style="normal">:message</text>
<text x="75" y="30" dominant-baseline="central">"Request Entity Too Large."</text>
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<text x="-25" y="0"><tspan text-anchor="end" font-style="normal" dominant-baseline="central">:resource-exists?</tspan><tspan>①</tspan></text>
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<text x="5" y="30" dominant-baseline="central" font-style="normal">:message</text>
<text x="75" y="30" dominant-baseline="central">"Not Found."</text>
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<use x="0" y="20" xlink:href="#entry"/>
<text x="5" y="30" dominant-baseline="central" font-style="normal">:message</text>
<text x="75" y="30" dominant-baseline="central">"OK."</text>
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<dl class=callouts>
<dt>①
<dd>This is a <em>decision function</em>.
<dt>②
<dd>This is a <em>handler function</em>.
</dl>
<p>As a developer you can specify <b>replacements</b> to both these types of function.
<p>For example, suppose we want to override the default 404
message. We can provide a replacement to
the <em>:handle-not-found</em> handler function when we define the
resource, like this:
<pre><code>(<span class="clojure symbol">compojure/ANY</span> <span class="clojure string">"/products/:sku"</span> [sku]
(<span class="clojure symbol">liberator/resource</span>
<span class="clojure keyword">:handle-not-found</span> (<span class="clojure symbol">fn</span>① [ctx②]
(<span class="clojure symbol">str</span> <span class="clojure string">"No such product: "</span> sku)③)))</code></pre>
<dl class=callouts>
<dt>①
<dd>We are providing a replacement function, but we could just as easily specify a constant or string value in this case. Constant values can be used in place of functions where appropriate.
<dt>②
<dd>This is the Liberator <em>context argument</em>. We'll come to this shortly.
<dt>③
<dd>We returned only a string here. Liberator is smart enough to turn this into a proper Ring response. This is a useful feature of Liberator, that it will coerce whatever you return into a correct Ring response, using whatever information it has already established (via content negotiation, etc.)
</dl>
<p>So the value which will be returned from the resource will be something like this :-
<pre><code>{:status 404
:body "No such product: 12345"}</code></pre>
<p>This will be processed by Ring to generate the final HTTP response.
<p>But shouldn't the body be valid HTML? This question assumes
that the user-agent (the software that sent us the request) is capable
of displaying HTML but we don't yet know that.
<p>Before we change the response body to valid HTML, let's
indicate to the user-agent that we are prepared to do so. We do
this via the <i>:available-media-types</i> argument.
<pre><code>(<span class="clojure symbol">compojure/ANY</span> <span class="clojure string">"/products/:sku"</span> [sku]
(<span class="clojure symbol">liberator/resource</span>
<span class="clojure keyword">:handle-not-found</span> (<span class="clojure symbol">fn</span> [ctx] (<span class="clojure symbol">str</span> <span class="clojure string">"No such product: "</span> sku))
<span class="code highlight"><span class="clojure keyword">:available-media-types</span> [<span class="clojure string">"text/html"</span> <span class="clojure string">"text/plain;q=0.8"</span>]</span>①))</code></pre>
<dl class=callouts>
<dt>①
<dd>This vector contains the mime-types of the
<em>representations</em> that we are able to support, HTML
(<code>text/html</code>) and plain-text
(<code>text/plain</code>). Each mime-type can be given an
optional <em>q-value</em> which indicates which
representation the resource would <i>prefer</i> to
generate. Note that the user-agent's preferred
representation (indicated by the Accept header) always
takes priority over this preference. The highest <em>q-value</em> wins and a
missing <em>q-value</em> implies a value of 1.
</dl>
</section>
<span class="anchor" id="flowchart"></span>
<section>
<h2>Understanding the flowchart</h2>
<p>Decisions are made according to a flowchart which determines
the order in which decisions and places where the path splits into
two.
<p>The flowchart always ends at a handler (at the bottom of the
chart) which determines the HTTP status code in the response.
<p>On deciding how to implemented the behaviour you have designed
for your resource you will often have this diagram in front of you
to decide which functions to replace.
<p>
<figure>
<figcaption>The Liberator flowchart (if you don't see anything below, please <a href="http://philipp.meier.name/t/liberator-flow-color.svg" target="_blank">open</a> it)</figcaption>
<a href="http://philipp.meier.name/t/liberator-flow-color.svg" target="_blank">
<object width="80%" height="80%" data="http://philipp.meier.name/t/liberator-flow-color.svg"></object>
</a>
</figure>
</p>
<p><small>Our diagrams are in SVG format. If your browser cannot
display SVG, there is also
a <a href="http://philipp.meier.name/t/liberator-flow-color.png">PNG</a>
version of this flowchart available.</small></p>
<p><small>Attribution: This diagram aligns with
the <a href="http://wiki.basho.com/Webmachine-Diagram.html">one
created by Alan Dean for webmachine</a>. We have made a few small changes to the naming of decisions (so that they can be represented by Clojure keys) and to include the side-effecting <tt>post!</tt>, <tt>put!</tt> and <tt>delete!</tt> actions.</small>
</section>
<span class="anchor" id="functions"></span>
<section>
<h2>Replacing functions</h2>
<h3>The context argument</h3>
<p>The context argument is provided as a single argument to all
replacement functions. It is a map of 5 entries.
<table id=context-arg dir=ltr border=1>
<style>
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<colgroup width=30% />
<colgroup width=1* style="background:#ddd;" />
<tbody>
<tr>
<td>:status
<td>The response status code
</tr>
<tr>
<td>:message
<td>The default status message that usually accompanies the status code
</tr>
<tr>
<td>:request
<td>The original Ring request
</tr>
<tr>
<td>:resource
<td>The resource map that defines the Liberator resource
</tr>
<tr>
<td>:representation
<td>This is a map containing the results of content negotiation. It contains 4 sub-keys :-
<ul>
<li>:media-type
<li>:language
<li>:charset
<li>:encoding
</ul>
</td>
</tr>
</tbody>
</table>
<h3>The return value</h3>
<p>For decision functions you usually return a boolean. However,
sometimes you want to store some state in the context to pass to
the next decisions and ultimately to the handler.
<p>
If you return a map, this will get merged into the context given
to future functions. Returning a map implies a true result, so
if you want to return a false result but also specify a map you
can do this by returning a vector pair containing the map,
ie. [false {}]
<p>For handler functions you have more flexibility. If you return
a map, it will be treated as a Ring response map. Anything else
will be treated as the :body value of a Ring reponse map, and the
rest of the details will be added by Liberator. It is possible in
this way to override the status code if necessary. Only do this if
you know what you're doing, but if you're sure Liberator won't
stand in your way.
<h3>Function reference</h3>
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<colgroup width=30% />
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<thead>
<tr><th>Key<th>Type<th>Purpose</tr>
</thead>
<tbody>
<tr><td class="decision">:allowed?<td>decision<td>Whether the user is allowed access to the resource. Returning false will cause a 403 Forbidden.</tr>
<tr><td class="decision">:authorized?<td>decision<td></tr>
<tr><td class="declaration">:available-charsets<td>declaration<td></tr>
<tr><td class="declaration">:available-encodings<td>declaration<td></tr>
<tr><td class="declaration">:available-languages<td>declaration<td></tr>
<tr><td class="declaration">:available-media-types<td>declaration<td></tr>
<tr class="advanced"><td class="decision">:can-post-to-missing?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:charset-available?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:conflict?<td>decision<td></tr>
<tr><td class="action">:delete!<td>action<td></tr>
<tr class="advanced"><td class="decision">:encoding-available?<td>decision<td></tr>
<tr class="advanced"><td class="declaration">:etag<td>declaration<td></tr>
<tr class="advanced"><td class="decision">:existed?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:exists?<td>decision<td></tr>
<tr class="advanced"><td class="handler">:handle-created<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-gone<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-malformed<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-method-not-allowed<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-multiple-representations<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-no-content<td>handler<td></tr>
<tr><td class="handler">:handle-not-acceptable<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-not-found<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-not-implemented<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-not-modified<td>handler<td></tr>
<tr><td class="handler">:handle-ok<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-precondition-failed<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-request-entity-too-large<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-service-not-available<td>handler<td></tr>
<tr><td class="handler">:handle-unsupported-media-type<td>handler<td></tr>
<tr class="advanced"><td class="handler">:handle-uri-too-long<td>handler<td></tr>
<tr class="advanced"><td class="decision">:known-content-type?<td>decision<td></tr>
<tr class="advanced"><td class="decision" >:known-method?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:language-available?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:malformed?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:method-allowed?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:multiple-representations?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:new?<td>decision<td></tr>
<tr><td class="action">:post!<td>action<td></tr>
<tr><td class="decision">:post-redirect?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:post-to-existing?<td>decision<td></tr>
<tr><td class="action">:put!<td>action<td></tr>
<tr class="advanced"><td class="decision">:put-to-different-url?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:respond-with-entity?<td>decision<td></tr>
<tr><td class="declaration">:see-other<td>declaration<td></tr>
<tr><td class="decision">:service-available?<td>decision<br>(Defaults to true)<td>Return false if, for some reason, you are no longer able to fulfill any requests, perhaps due to capacity issues. (You've just appeared on Hacker News!)</tr>
<tr><td class="handler">:unauthorized<td>handler<td></tr>
<tr class="advanced"><td class="handler">:unknown-method<td>handler<td></tr>
<tr class="advanced"><td class="decision">:uri-too-long?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:valid-content-header?<td>decision<td></tr>
<tr class="advanced"><td class="decision">:valid-entity-length?<td>decision<td></tr>
</table>
</section>
<span class="anchor" id="getting-started"></span>
<section>
<h2>Getting started</h2>
<p>For this bit, please use <a href="http://leiningen.org">leiningen 2</a>.</p>
<p>Create a new project
<pre>> <kbd>lein new myproj</kbd></pre>
<p>Edit the <code>project.clj</code> file so that the <code>liberator</code> dependency is added.
<pre><code>(<span class="clojure symbol">defproject</span> myproj <span class="clojure string">"0.0.1"</span>
<span class="clojure keyword">:dependencies</span> [...
[liberator <span class="clojure string">"0.8.0"</span>]])</code></pre>
<p>Start the REPL
<pre>> <kbd>lein repl</kbd></pre>
<p>Import liberator
<pre>REPL> <kbd>(use 'liberator.core)</kbd></pre>
<h3>Running the examples</h3>
<p>A set of examples is included. If you want to see the examples in a browser, run
<pre>> <kbd>lein examples</kbd></pre>
<p>This will start a web server on port 8000 (but you can specify a alternative port with an argument, eg. <kbd>lein examples 8001</kbd>). Alternatively you can run the web server with <kbd>lein ring server</kbd>).
<h3>Swank users</h3>
<p>If you code in Emacs (with Slime) and want to use swank, ensure
you have the lein swank plugin installed. For example, ensure you have included the lein-swank plugin in your <tt>$HOME/.lein/profiles.clj</tt> file :-
<pre>
{<span class="clojure keyword">:user</span> {<span class="clojure keyword">:plugins</span> [[<span class="clojure symbol">lein-swank</span> <span class="clojure string">"1.4.4"</span>]]}}
</pre>
<p>Now you can use leiningen to start the swank server :-
<pre>> <kbd>lein swank</kbd></pre>
<p>In Emacs, execute <tt>M-x slime-connect</tt> and wait for the REPL to start. To start the examples server, type the following commands into the Emacs REPL :-
<pre>
user> <kbd>(require 'examples.server)</kbd>
user> <kbd>(examples.server/-main)</kbd></pre>
<p>Now open <tt>examples/clj/examples.clj</tt> and add a new route to the top of the <tt>assemble-routes</tt> function. Re-eval the buffer and test in the browser. Happy hacking!</p>
<pre>
(<span class="clojure symbol">defn</span> assemble-routes []
(<span class="clojure symbol">routes</span>
<span class="code highlight">(<span class="clojure symbol">ANY</span> <span class="clojure string">"/my-example"</span> [] (<span class="clojure symbol">resource</span> <span class="clojure keyword">:handle-ok</span> <span class="clojure string">"My example..."</span>))</span>
(<span class="clojure symbol">ANY</span> <span class="clojure string">"/hello-world"</span> [] <span class="clojure symbol">hello-world</span>)
...
))</pre>