<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <link rel="STYLESHEET" href="modpython.css" type='text/css' /> <link rel="first" href="modpython.html" title='Mod_python Manual' /> <link rel='contents' href='contents.html' title="Contents" /> <link rel='index' href='genindex.html' title='Index' /> <link rel='last' href='about.html' title='About this document...' /> <link rel='help' href='about.html' title='About this document...' /> <link rel="next" href="pyapi-filter.html" /> <link rel="prev" href="pyapi-interps.html" /> <link rel="parent" href="pythonapi.html" /> <link rel="next" href="pyapi-filter.html" /> <meta name='aesop' content='information' /> <title>4.2 Overview of a Request Handler</title> </head> <body> <DIV CLASS="navigation"> <div id='top-navigation-panel' xml:id='top-navigation-panel'> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="4.1 Multiple Interpreters" href="pyapi-interps.html"><img src='previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="4. 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Python API</A> <b class="navlabel">Next:</b> <a class="sectref" rel="next" href="pyapi-filter.html">4.3 Overview of a</A> </div> <hr /></div> </DIV> <!--End of Navigation Panel--> <H1><A NAME="SECTION006200000000000000000"></A><A NAME="pyapi-handler"></A> <BR> 4.2 Overview of a Request Handler </H1> <a id='l2h-24' xml:id='l2h-24'></a> <P> A <i class="dfn">handler</i> is a function that processes a particular phase of a request. Apache processes requests in phases - read the request, process headers, provide content, etc. For every phase, it will call handlers, provided by either the Apache core or one of its modules, such as mod_python which passes control to functions provided by the user and written in Python. A handler written in Python is not any different from a handler written in C, and follows these rules: <P> <a id='l2h-26' xml:id='l2h-26'></a> <a id='l2h-25' xml:id='l2h-25'></a> A handler function will always be passed a reference to a request object. (Throughout this manual, the request object is often referred to by the <code>req</code> variable.) <P> Every handler can return: <P> <UL> <LI><tt class="constant">apache.OK</tt>, meaning this phase of the request was handled by this handler and no errors occurred. <P> </LI> <LI><tt class="constant">apache.DECLINED</tt>, meaning this handler has not handled this phase of the request to completion and Apache needs to look for another handler in subsequent modules. <P> </LI> <LI><tt class="constant">apache.<em>HTTP_ERROR</em></tt>, meaning an HTTP error occurred. <var>HTTP_ERROR</var> can be any of the following: <P> <div class="verbatim"><pre> HTTP_CONTINUE = 100 HTTP_SWITCHING_PROTOCOLS = 101 HTTP_PROCESSING = 102 HTTP_OK = 200 HTTP_CREATED = 201 HTTP_ACCEPTED = 202 HTTP_NON_AUTHORITATIVE = 203 HTTP_NO_CONTENT = 204 HTTP_RESET_CONTENT = 205 HTTP_PARTIAL_CONTENT = 206 HTTP_MULTI_STATUS = 207 HTTP_MULTIPLE_CHOICES = 300 HTTP_MOVED_PERMANENTLY = 301 HTTP_MOVED_TEMPORARILY = 302 HTTP_SEE_OTHER = 303 HTTP_NOT_MODIFIED = 304 HTTP_USE_PROXY = 305 HTTP_TEMPORARY_REDIRECT = 307 HTTP_BAD_REQUEST = 400 HTTP_UNAUTHORIZED = 401 HTTP_PAYMENT_REQUIRED = 402 HTTP_FORBIDDEN = 403 HTTP_NOT_FOUND = 404 HTTP_METHOD_NOT_ALLOWED = 405 HTTP_NOT_ACCEPTABLE = 406 HTTP_PROXY_AUTHENTICATION_REQUIRED= 407 HTTP_REQUEST_TIME_OUT = 408 HTTP_CONFLICT = 409 HTTP_GONE = 410 HTTP_LENGTH_REQUIRED = 411 HTTP_PRECONDITION_FAILED = 412 HTTP_REQUEST_ENTITY_TOO_LARGE = 413 HTTP_REQUEST_URI_TOO_LARGE = 414 HTTP_UNSUPPORTED_MEDIA_TYPE = 415 HTTP_RANGE_NOT_SATISFIABLE = 416 HTTP_EXPECTATION_FAILED = 417 HTTP_UNPROCESSABLE_ENTITY = 422 HTTP_LOCKED = 423 HTTP_FAILED_DEPENDENCY = 424 HTTP_INTERNAL_SERVER_ERROR = 500 HTTP_NOT_IMPLEMENTED = 501 HTTP_BAD_GATEWAY = 502 HTTP_SERVICE_UNAVAILABLE = 503 HTTP_GATEWAY_TIME_OUT = 504 HTTP_VERSION_NOT_SUPPORTED = 505 HTTP_VARIANT_ALSO_VARIES = 506 HTTP_INSUFFICIENT_STORAGE = 507 HTTP_NOT_EXTENDED = 510 </pre></div> <P> </LI> </UL> <P> As an alternative to <em>returning</em> an HTTP error code, handlers can signal an error by <em>raising</em> the <tt class="constant">apache.SERVER_RETURN</tt> exception, and providing an HTTP error code as the exception value, e.g. <P> <div class="verbatim"><pre> raise apache.SERVER_RETURN, apache.HTTP_FORBIDDEN </pre></div> <P> Handlers can send content to the client using the <tt class="method">req.write()</tt> method. <P> Client data, such as POST requests, can be read by using the <tt class="method">req.read()</tt> function. <P> <div class="note"><b class="label">Note:</b> The directory of the Apache <code>Python*Handler</code> directive in effect is prepended to the <code>sys.path</code>. If the directive was specified in a server config file outside any <code><Directory></code>, then the directory is unknown and not prepended. </div> <P> An example of a minimalistic handler might be: <P> <div class="verbatim"><pre> from mod_python import apache def requesthandler(req): req.content_type = "text/plain" req.write("Hello World!") return apache.OK </pre></div> <P> <DIV CLASS="navigation"> <div class='online-navigation'> <p></p><hr /> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="4.1 Multiple Interpreters" href="pyapi-interps.html"><img src='previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="4. Python API" href="pythonapi.html"><img src='up.png' border='0' height='32' alt='Up One Level' width='32' /></A></td> <td class='online-navigation'><a rel="next" title="4.3 Overview of a" href="pyapi-filter.html"><img src='next.png' border='0' height='32' alt='Next Page' width='32' /></A></td> <td align="center" width="100%">Mod_python Manual</td> <td class='online-navigation'><a rel="contents" title="Table of Contents" href="contents.html"><img src='contents.png' border='0' height='32' alt='Contents' width='32' /></A></td> <td class='online-navigation'><img src='blank.png' border='0' height='32' alt='' width='32' /></td> <td class='online-navigation'><a rel="index" title="Index" href="genindex.html"><img src='index.png' border='0' height='32' alt='Index' width='32' /></A></td> </tr></table> <div class='online-navigation'> <b class="navlabel">Previous:</b> <a class="sectref" rel="prev" href="pyapi-interps.html">4.1 Multiple Interpreters</A> <b class="navlabel">Up:</b> <a class="sectref" rel="parent" href="pythonapi.html">4. Python API</A> <b class="navlabel">Next:</b> <a class="sectref" rel="next" href="pyapi-filter.html">4.3 Overview of a</A> </div> </div> <hr /> <span class="release-info">Release 3.3.1, documentation updated on January 29, 2007.</span> </DIV> <!--End of Navigation Panel--> </BODY> </HTML>