doc/web/howto/web-in-60/custom-codes.html

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   3 <title>Twisted Documentation: Custom Response Codes</title>
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   8     <h1 class="title">Custom Response Codes</h1>
   9     <div class="toc"><ol/></div>
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  11 <span/>
  12
  13 <p>The previous example introduced <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.error.NoResource.html" title="twisted.web.error.NoResource">NoResource</a></code>, a Twisted Web error resource which
  14 responds with a 404 (not found) code. This example will cover the APIs
  15 that <code>NoResource</code> uses to do this so that you can generate your own
  16 custom response codes as desired.</p>
  17
  18 <p>First, the now-standard import preamble:</p>
  19
  20 <pre class="python"><p class="py-linenumber">1
  21 2
  22 3
  23 </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>
  24 <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>
  25 <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>
  26 </pre>
  27
  28 <p>Now we'll define a new resource class that always returns a 402 (payment
  29 required) response. This is really not very different from the resources that
  30 was defined in previous examples. The fact that it has a response code other
  31 than 200 doesn't change anything else about its role. This will require using
  32 the request object, though, which none of the previous examples have done.</p>
  33
  34 <p>The <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.server.Request.html" title="twisted.web.server.Request">Request</a></code> object has
  35 shown up in a couple of places, but so far we've ignored it. It is a parameter
  36 to the <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>
  37 API as well as to render methods such as <code>render_GET</code>. As you might
  38 have suspected, it represents the request for which a response is to be
  39 generated. Additionally, it also represents the response being generated. In
  40 this example we're going to use its <code class="API"><a href="http://twistedmatrix.com/documents/12.1.0/api/twisted.web.http.Request.setResponseCode.html" title="twisted.web.http.Request.setResponseCode">setResponseCode</a></code> method to - you guessed
  41 it - set the response's status code.</p>
  42
  43 <pre class="python"><p class="py-linenumber">1
  44 2
  45 3
  46 4
  47 </p><span class="py-src-keyword">class</span> <span class="py-src-identifier">PaymentRequired</span>(<span class="py-src-parameter">Resource</span>):
  48     <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>):
  49         <span class="py-src-variable">request</span>.<span class="py-src-variable">setResponseCode</span>(<span class="py-src-number">402</span>)
  50         <span class="py-src-keyword">return</span> <span class="py-src-string">&quot;&lt;html&gt;&lt;body&gt;Please swipe your credit card.&lt;/body&gt;&lt;/html&gt;&quot;</span>
  51 </pre>
  52
  53 <p>Just like the other resources I've demonstrated, this one returns a
  54 string from its <code>render_GET</code> method to define the body of
  55 the response. All that's different is the call
  56 to <code>setResponseCode</code> to override the default response code,
  57 200, with a different one.</p>
  58
  59 <p>Finally, the code to set up the site and reactor. We'll put an instance of
  60 the above defined resource at <code>/buy</code>:</p>
  61
  62 <pre class="python"><p class="py-linenumber">1
  63 2
  64 3
  65 4
  66 5
  67 </p><span class="py-src-variable">root</span> = <span class="py-src-variable">Resource</span>()
  68 <span class="py-src-variable">root</span>.<span class="py-src-variable">putChild</span>(<span class="py-src-string">&quot;buy&quot;</span>, <span class="py-src-variable">PaymentRequired</span>())
  69 <span class="py-src-variable">factory</span> = <span class="py-src-variable">Site</span>(<span class="py-src-variable">root</span>)
  70 <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>)
  71 <span class="py-src-variable">reactor</span>.<span class="py-src-variable">run</span>()
  72 </pre>
  73
  74 <p>Here's the complete example:</p>
  75
  76 <pre class="python"><p class="py-linenumber"> 1
  77  2
  78  3
  79  4
  80  5
  81  6
  82  7
  83  8
  84  9
  85 10
  86 11
  87 12
  88 13
  89 14
  90 </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>
  91 <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>
  92 <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>
  93
  94 <span class="py-src-keyword">class</span> <span class="py-src-identifier">PaymentRequired</span>(<span class="py-src-parameter">Resource</span>):
  95     <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>):
  96         <span class="py-src-variable">request</span>.<span class="py-src-variable">setResponseCode</span>(<span class="py-src-number">402</span>)
  97         <span class="py-src-keyword">return</span> <span class="py-src-string">&quot;&lt;html&gt;&lt;body&gt;Please swipe your credit card.&lt;/body&gt;&lt;/html&gt;&quot;</span>
  98
  99 <span class="py-src-variable">root</span> = <span class="py-src-variable">Resource</span>()
 100 <span class="py-src-variable">root</span>.<span class="py-src-variable">putChild</span>(<span class="py-src-string">&quot;buy&quot;</span>, <span class="py-src-variable">PaymentRequired</span>())
 101 <span class="py-src-variable">factory</span> = <span class="py-src-variable">Site</span>(<span class="py-src-variable">root</span>)
 102 <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>)
 103 <span class="py-src-variable">reactor</span>.<span class="py-src-variable">run</span>()
 104 </pre>
 105
 106 <p>Run the server and visit <code>http://localhost:8880/buy</code> in your
 107 browser. It'll look pretty boring, but if you use Firefox's View Page Info
 108 right-click menu item (or your browser's equivalent), you'll be able to see that
 109 the server indeed sent back a 402 response code.</p>
 110
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