<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>4.2 Overview of a Request Handler</title> <META NAME="description" CONTENT="4.2 Overview of a Request Handler"> <META NAME="keywords" CONTENT="modpython"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <link rel="STYLESHEET" href="modpython.css"> <link rel="first" href="modpython.html"> <link rel="contents" href="contents.html" title="Contents"> <link rel="index" href="genindex.html" title="Index"> <LINK REL="next" href="pyapi-filter.html"> <LINK REL="previous" href="pyapi-interps.html"> <LINK REL="up" href="pythonapi.html"> <LINK REL="next" href="pyapi-filter.html"> </head> <body> <DIV CLASS="navigation"> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A href="pyapi-interps.html"><img src="icons/previous.png" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="pythonapi.html"><img src="icons/up.png" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="pyapi-filter.html"><img src="icons/next.png" border="0" height="32" alt="Next Page" width="32"></A></td> <td align="center" width="100%">Mod_python Manual</td> <td><A href="contents.html"><img src="icons/contents.png" border="0" height="32" alt="Contents" width="32"></A></td> <td><img src="icons/blank.png" border="0" height="32" alt="" width="32"></td> <td><A href="genindex.html"><img src="icons/index.png" border="0" height="32" alt="Index" width="32"></A></td> </tr></table> <b class="navlabel">Previous:</b> <a class="sectref" href="pyapi-interps.html">4.1 Multiple Interpreters</A> <b class="navlabel">Up:</b> <a class="sectref" href="pythonapi.html">4. Python API</A> <b class="navlabel">Next:</b> <a class="sectref" href="pyapi-filter.html">4.3 Overview of a</A> <br><hr> </DIV> <!--End of Navigation Panel--> <H1><A NAME="SECTION006200000000000000000"> </A> <BR> 4.2 Overview of a Request Handler </H1> <a name="l2h-13"> </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 name="l2h-14"> </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.<i>HTTP_ERROR</i></tt>, meaning an HTTP error occurred. <var>HTTP_ERROR</var> can be any of the following: <P> <dl><dd><pre class="verbatim"> 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></dl> <P> </LI> </UL> <P> As an alternative to <i>returning</i> an HTTP error code, handlers can signal an error by <i>raising</i> the <tt class="constant">apache.SERVER_RETURN</tt> exception, and providing an HTTP error code as the exception value, e.g. <P> <dl><dd><pre class="verbatim"> raise apache.SERVER_RETURN, apache.HTTP_FORBIDDEN </pre></dl> <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> <dl><dd><pre class="verbatim"> from mod_python import apache def requesthandler(req): req.content_type = "text/plain" req.write("Hello World!") return apache.OK </pre></dl> <P> <DIV CLASS="navigation"> <p><hr> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A href="pyapi-interps.html"><img src="icons/previous.png" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="pythonapi.html"><img src="icons/up.png" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="pyapi-filter.html"><img src="icons/next.png" border="0" height="32" alt="Next Page" width="32"></A></td> <td align="center" width="100%">Mod_python Manual</td> <td><A href="contents.html"><img src="icons/contents.png" border="0" height="32" alt="Contents" width="32"></A></td> <td><img src="icons/blank.png" border="0" height="32" alt="" width="32"></td> <td><A href="genindex.html"><img src="icons/index.png" border="0" height="32" alt="Index" width="32"></A></td> </tr></table> <b class="navlabel">Previous:</b> <a class="sectref" href="pyapi-interps.html">4.1 Multiple Interpreters</A> <b class="navlabel">Up:</b> <a class="sectref" href="pythonapi.html">4. Python API</A> <b class="navlabel">Next:</b> <a class="sectref" href="pyapi-filter.html">4.3 Overview of a</A> <hr> <span class="release-info">Release 3.1.0a, documentation updated on August 26, 2003.</span> </DIV> <!--End of Navigation Panel--> </BODY> </HTML>