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<h1>Adding new content viewers</h1>
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<p>As discussed in <a href="../mitmproxy.html">the Flow View section of the mitmproxy overview</a>, mitmproxy allows you to inspect and manipulate flows. When inspecting a single flow, mitmproxy uses a number of heuristics to show a friendly view of various content types; if mitmproxy cannot show a friendly view, mitmproxy defaults to a <strong>raw</strong> view.</p>
<p>By default, mitmproxy has support for displaying the following content types in a friendly view:</p>
<ul>
<li><strong>1</strong>: Hex</li>
<li><strong>2</strong>: HTML</li>
<li><strong>3</strong>: Image</li>
<li><strong>4</strong>: JavaScript</li>
<li><strong>5</strong>: JSON</li>
<li><strong>6</strong>: URL-encoded data</li>
<li><strong>7</strong>: XML</li>
<li><strong>8</strong>: AMF (requires PyAMF)</li>
<li><strong>9</strong>: Protobuf (requires protobuf library)</li>
</ul>
<p>Each content type invokes a different flow viewer to parse the data and display the friendly view. Users can add custom content viewers by adding a view class to contentview.py, discussed below.</p>
<h2>Adding a new View class to contentview.py</h2>
<p>The content viewers used by mitmproxy to present a friendly view of various content types are stored in contentview.py. Reviewing this file shows a number of classes named ViewSomeDataType, each with the properties: <strong>name</strong>, <strong>prompt</strong>, and <strong>content_types</strong> and a function named <strong>__call__</strong>.</p>
<p>Adding a new content viewer to parse a data type is as simple as writing a new View class. Your new content viewer View class should have the same properties as the other View classes: <strong>name</strong>, <strong>prompt</strong>, and <strong>content_types</strong> and a <strong>__call__</strong> function to parse the content of the request/response. </p>
<ul>
<li>The <strong>name</strong> property should be a string describing the contents and new content viewer; </li>
<li><p>The <strong>prompt</strong> property should be a two item tuple:</p>
<ul>
<li><strong>1</strong>: A string that will be used to display the new content viewer's type; and</li>
<li><strong>2</strong>: A one character string that will be the hotkey used to select the new content viewer from the Flow View screen; </li>
</ul></li>
<li><p>The <strong>content_types</strong> property should be a list of strings of HTTP Content-Types that the new content viewer can parse. </p>
<ul>
<li>Note that mitmproxy will use the content_types to try and heuristically show a friendly view of content and that you can override the built-in views by populating content_types with values for content_types that are already parsed -- e.g. "image/png".</li>
</ul></li>
</ul>
<p>After defining the <strong>name</strong>, <strong>prompt</strong>, and <strong>content_types</strong> properties of the class, you should write the <strong>__call__</strong> function, which will parse the request/response data and provide a friendly view of the data. The <strong>__call__</strong> function should take the following arguments: <strong>self</strong>, <strong>hdrs</strong>, <strong>content</strong>, <strong>limit</strong>; <strong>hdrs</strong> is a ODictCaseless object containing the headers of the request/response; <strong>content</strong> is the content of the request/response, and <strong>limit</strong> is an integer representing the amount of data to display in the view window.</p>
<p>The <strong>__call__</strong> function returns two values: (1) a string describing the parsed data; and (2) the parsed data for friendly display. The parsed data to be displayed should be a list of strings formatted for display. You can use the <strong>_view_text</strong> function in contentview.py to format text for display. Alternatively, you can display content as a series of key-value pairs; to do so, prepare a list of lists, where each list item is a two item list -- a key that describes the data, and then the data itself; after preparing the list of lists, use the <strong>common.format_keyvals</strong> function on it to prepare it as text for display. </p>
<p>If the new content viewer fails or throws an exception, mitmproxy will default to a <strong>raw</strong> view.</p>
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