122 lines
4.8 KiB
HTML
122 lines
4.8 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="author" content="Basho Technologies" />
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<meta name="description" content="Webmachine request dispatching" />
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<meta name="keywords" content="webmachine http rest web" />
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<meta http-equiv="content-type" content="text/html;charset=utf-8" />
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<link rel="stylesheet" href="css/style-1c.css" type="text/css" />
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<title>Webmachine request dispatching</title>
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</head>
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<body>
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<div id="content">
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<h1><span class="hr"></span><a href="/">webmachine</a></h1>
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<ul id="top">
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<li><a href="/">Home</a></li>
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<li><a href="http://bitbucket.org/justin/webmachine/">Source Code</a></li>
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<li><a href="contact.html">Contact</a></li>
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</ul>
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<div id="left">
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<h3>Webmachine request dispatching</h3>
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<p>
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This page describes the configuration of URI dispatch to resources
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in a webmachine application. The dispatch map data structure is a list
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of 3-tuples, where each entry is of the form {pathspec, resource,
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args}. The first pathspec in the list that matches the URI for a
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request will cause the corresponding resource to be used in handling
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that request.
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</p>
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<p>
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A <code>pathspec</code> is a list of pathterms. A pathterm is any of
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[string,atom,star] where star is just the atom of "*". The
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pathspec-matching is done by breaking up the request URI into tokens
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via the "/" separator and matching those tokens against the
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pathterms. A string pathterm will match a token if the token is equal
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to that string. A non-star atom will match any single token. The star
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atom (* in single quotes) will match any number of tokens, but may
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only be present as the last pathterm in a pathspec. If all tokens are
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matched and all pathterms are used, then the pathspec matches. The
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tokens used are available in <code>wrq:path_tokens(ReqData)</code>
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in the resource functions.
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</p>
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<p>
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Any atom pathterms that were used in a match will cause a binding in
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the path_info element of the request's
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<a href="reqdata.html">ReqData</a>. If
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there was a <code>foo</code> atom that matched the token
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<code>"bar"</code>, then <code>wrq:path_info(foo, ReqData)</code> will
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return <code>"bar"</code> inside the resource calls, and in any case
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<code>wrq:path_info(ReqData)</code> will return a Dict term with all
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the bindings, accessible via the <code>dict</code> standard library
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module. If there was a star pathterm in the pathspec, then
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<code>wrq:disp_path(ReqData)</code> in a resource function will return
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the URI portion that was matched by the star.
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</p>
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<p>
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The <code> resource </code> is an atom identifying a
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<a href="resources.html">resource</a> that
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should handle a matching request. It will have the <code>args</code>
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(which must be a list) passed to its init function before request
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handling begins.
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</p>
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<p>
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In the default directory structure for a new webmachine application,
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the dispatch terms will be in file:consult form in
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"priv/dispatch.conf" under the application root.
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</p>
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<h3 id="examples">Examples</h3>
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<p>
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The examples below are taken from
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<a href="http://www.erlang-factory.com/conference/SFBayAreaErlangFactory2009/speakers/justinsheehy">Justin Sheehy's slide at Erlang Factory 2009</a>
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</p>
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<table><tr><th>Dispatch Rule</th><th>URL</th><th>wrq:disp_path</th><th>wrq:path</th><th>wrq:path_info</th><th>wrq:path_tokens</th></tr>
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<tr><td>{["a"], some_resource, []}</td><td>/a</td><td>""</td><td>"/a"</td><td>[]</td><td>[]</td></tr>
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<tr><td>{["a", '*'], some_resource, []}</td><td>/a</td><td>""</td><td>"/a"</td><td>[]</td><td>[]</td></tr>
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<tr><td>{["a", '*'], some_resource, []}</td><td>/a/b/c</td><td>"b/c"</td><td>"/a/b/c"</td><td>[]</td><td>["b", "c"]</td></tr>
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<tr><td>{["a", foo], some_resource, []}</td><td>/a/b</td><td>""</td><td>"/a/b"</td><td>[{foo, "b"}]</td><td>[]</td></tr>
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<tr><td>{["a", foo, '*'], some_resource, []}</td><td>/a/b</td><td>""</td><td>"/a/b"</td><td>[{foo, "b"}]</td><td>[]</td></tr>
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<tr><td>{["a", foo, '*'], some_resource, []}</td><td>/a/b/c/d</td><td>"c/d"</td><td>"/a/b/c/d"</td><td>[{foo, "b"}]</td><td>["c", "d"]</td></tr>
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</table>
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<p>Query strings are easy too:</p>
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<ul><li>Given rule: {["a", foo, '*'], some_resource, []}
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</li><li>And URL: /a/b/c/d?fee=ah&fie=ha
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</li><li>Then wrq:get_qs_value("fie",ReqData) -> "ha"
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</li></ul>
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</div>
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