doc/web/howto/web-in-60/dynamic-dispatch.html

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   3 <title>Twisted Documentation: Dynamic URL Dispatch</title>
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   8     <h1 class="title">Dynamic URL Dispatch</h1>
   9     <div class="toc"><ol/></div>
  10     <div class="content">
  11 <span/>
  12
  13 <p>In the <a href="static-dispatch.html" shape="rect">previous example</a> we covered how to
  14 statically configure Twisted Web to serve different content at different
  15 URLs. The goal of this example is to show you how to do this dynamically
  16 instead. Reading the previous installment if you haven't already is suggested in
  17 order to get an overview of how URLs are treated when using Twisted Web's <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.resource.html" title="twisted.web.resource">resource</a></code> APIs.</p>
  18
  19 <p><code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.server.Site.html" title="twisted.web.server.Site">Site</a></code> (the object which
  20 associates a listening server port with the HTTP implementation), <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.resource.Resource.html" title="twisted.web.resource.Resource">Resource</a></code> (a convenient base class
  21 to use when defining custom pages), and <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.internet.reactor.html" title="twisted.internet.reactor">reactor</a></code> (the object which implements the Twisted
  22 main loop) return once again:</p>
  23
  24 <pre class="python"><p class="py-linenumber">1
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  27 </p><span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">web</span>.<span class="py-src-variable">server</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">Site</span>
  28 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">web</span>.<span class="py-src-variable">resource</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">Resource</span>
  29 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">reactor</span>
  30 </pre>
  31
  32 <p>With that out of the way, here's the interesting part of this
  33 example. We're going to define a resource which renders a whole-year
  34 calendar. The year it will render the calendar for will be the year in
  35 the request URL. So, for example, <code>/2009</code> will render a
  36 calendar for 2009. First, here's a resource that renders a calendar
  37 for the year passed to its initializer:</p>
  38
  39 <pre class="python"><p class="py-linenumber">1
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  48 </p><span class="py-src-keyword">from</span> <span class="py-src-variable">calendar</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">calendar</span>
  49
  50 <span class="py-src-keyword">class</span> <span class="py-src-identifier">YearPage</span>(<span class="py-src-parameter">Resource</span>):
  51     <span class="py-src-keyword">def</span> <span class="py-src-identifier">__init__</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">year</span>):
  52         <span class="py-src-variable">Resource</span>.<span class="py-src-variable">__init__</span>(<span class="py-src-variable">self</span>)
  53         <span class="py-src-variable">self</span>.<span class="py-src-variable">year</span> = <span class="py-src-variable">year</span>
  54
  55     <span class="py-src-keyword">def</span> <span class="py-src-identifier">render_GET</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">request</span>):
  56         <span class="py-src-keyword">return</span> <span class="py-src-string">&quot;&lt;html&gt;&lt;body&gt;&lt;pre&gt;%s&lt;/pre&gt;&lt;/body&gt;&lt;/html&gt;&quot;</span> % (<span class="py-src-variable">calendar</span>(<span class="py-src-variable">self</span>.<span class="py-src-variable">year</span>),)
  57 </pre>
  58
  59 <p>Pretty simple - not all that different from the first dynamic resource
  60 demonstrated in <a href="dynamic-content.html" shape="rect">Generating a Page
  61 Dynamically</a>. Now here's the resource that handles URLs with a year in them
  62 by creating a suitable instance of this <code>YearPage</code> class:</p>
  63
  64 <pre class="python"><p class="py-linenumber">1
  65 2
  66 3
  67 </p><span class="py-src-keyword">class</span> <span class="py-src-identifier">Calendar</span>(<span class="py-src-parameter">Resource</span>):
  68   <span class="py-src-keyword">def</span> <span class="py-src-identifier">getChild</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">name</span>, <span class="py-src-parameter">request</span>):
  69       <span class="py-src-keyword">return</span> <span class="py-src-variable">YearPage</span>(<span class="py-src-variable">int</span>(<span class="py-src-variable">name</span>))
  70 </pre>
  71
  72 <p>By implementing <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.resource.Resource.getChild.html" title="twisted.web.resource.Resource.getChild">getChild</a></code> here, we've just defined
  73 how Twisted Web should find children of <code>Calendar</code> instances when
  74 it's resolving an URL into a resource. This implementation defines all integers
  75 as the children of <code>Calendar</code> (and punts on error handling, more on
  76 that later).</p>
  77
  78 <p>All that's left is to create a <code>Site</code> using this resource as its
  79 root and then start the reactor:</p>
  80
  81 <pre xml:space="preserve">
  82 root = Calendar()
  83 factory = Site(root)
  84 reactor.listenTCP(8880, factory)
  85 reactor.run()
  86 </pre>
  87
  88 <p>And that's all. Any resource-based dynamic URL handling is going to look
  89 basically like <code>Calendar.getPage</code>. Here's the full example code:</p>
  90
  91 <pre class="python"><p class="py-linenumber"> 1
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 112 22
 113 </p><span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">web</span>.<span class="py-src-variable">server</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">Site</span>
 114 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">web</span>.<span class="py-src-variable">resource</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">Resource</span>
 115 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">reactor</span>
 116
 117 <span class="py-src-keyword">from</span> <span class="py-src-variable">calendar</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">calendar</span>
 118
 119 <span class="py-src-keyword">class</span> <span class="py-src-identifier">YearPage</span>(<span class="py-src-parameter">Resource</span>):
 120     <span class="py-src-keyword">def</span> <span class="py-src-identifier">__init__</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">year</span>):
 121         <span class="py-src-variable">Resource</span>.<span class="py-src-variable">__init__</span>(<span class="py-src-variable">self</span>)
 122         <span class="py-src-variable">self</span>.<span class="py-src-variable">year</span> = <span class="py-src-variable">year</span>
 123
 124     <span class="py-src-keyword">def</span> <span class="py-src-identifier">render_GET</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">request</span>):
 125         <span class="py-src-keyword">return</span> <span class="py-src-string">&quot;&lt;html&gt;&lt;body&gt;&lt;pre&gt;%s&lt;/pre&gt;&lt;/body&gt;&lt;/html&gt;&quot;</span> % (<span class="py-src-variable">calendar</span>(<span class="py-src-variable">self</span>.<span class="py-src-variable">year</span>),)
 126
 127 <span class="py-src-keyword">class</span> <span class="py-src-identifier">Calendar</span>(<span class="py-src-parameter">Resource</span>):
 128   <span class="py-src-keyword">def</span> <span class="py-src-identifier">getChild</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">name</span>, <span class="py-src-parameter">request</span>):
 129       <span class="py-src-keyword">return</span> <span class="py-src-variable">YearPage</span>(<span class="py-src-variable">int</span>(<span class="py-src-variable">name</span>))
 130
 131 <span class="py-src-variable">root</span> = <span class="py-src-variable">Calendar</span>()
 132 <span class="py-src-variable">factory</span> = <span class="py-src-variable">Site</span>(<span class="py-src-variable">root</span>)
 133 <span class="py-src-variable">reactor</span>.<span class="py-src-variable">listenTCP</span>(<span class="py-src-number">8880</span>, <span class="py-src-variable">factory</span>)
 134 <span class="py-src-variable">reactor</span>.<span class="py-src-variable">run</span>()
 135 </pre>
 136
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