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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
| commit | e8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch) | |
| tree | aa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en | |
| parent | cc40af334e619bb549038238507407866f774f8f (diff) | |
upload http
JIRA: BOTTLENECK-10
Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en')
| -rw-r--r-- | rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en | 166 |
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diff --git a/rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en b/rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en new file mode 100644 index 00000000..20c83e6c --- /dev/null +++ b/rubbos/app/httpd-2.0.64/docs/manual/rewrite/rewrite_tech.html.en @@ -0,0 +1,166 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>Apache mod_rewrite Technical Details - Apache HTTP Server</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /> +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body id="manual-page"><div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.0</p> +<img alt="" src="../images/feather.gif" /></div> +<div class="up"><a href="./index.html"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Apache mod_rewrite Technical Details</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_tech.html" title="English"> en </a></p> +</div> + +<p>This document discusses some of the technical details of mod_rewrite +and URL matching.</p> +</div> +<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#Internal">Internal Processing</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#InternalAPI">API Phases</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#InternalRuleset">Ruleset Processing</a></li> +</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module +documentation</a></li><li><a href="rewrite_intro.html">mod_rewrite +introduction</a></li><li><a href="rewrite_guide.html">Practical solutions to common +problems</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="Internal" id="Internal">Internal Processing</a></h2> + + <p>The internal processing of this module is very complex but + needs to be explained once even to the average user to avoid + common mistakes and to let you exploit its full + functionality.</p> +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="InternalAPI" id="InternalAPI">API Phases</a></h2> + + <p>First you have to understand that when Apache processes a + HTTP request it does this in phases. A hook for each of these + phases is provided by the Apache API. Mod_rewrite uses two of + these hooks: the URL-to-filename translation hook which is + used after the HTTP request has been read but before any + authorization starts and the Fixup hook which is triggered + after the authorization phases and after the per-directory + config files (<code>.htaccess</code>) have been read, but + before the content handler is activated.</p> + + <p>So, after a request comes in and Apache has determined the + corresponding server (or virtual server) the rewriting engine + starts processing of all mod_rewrite directives from the + per-server configuration in the URL-to-filename phase. A few + steps later when the final data directories are found, the + per-directory configuration directives of mod_rewrite are + triggered in the Fixup phase. In both situations mod_rewrite + rewrites URLs either to new URLs or to filenames, although + there is no obvious distinction between them. This is a usage + of the API which was not intended to be this way when the API + was designed, but as of Apache 1.x this is the only way + mod_rewrite can operate. To make this point more clear + remember the following two points:</p> + + <ol> + <li>Although mod_rewrite rewrites URLs to URLs, URLs to + filenames and even filenames to filenames, the API + currently provides only a URL-to-filename hook. In Apache + 2.0 the two missing hooks will be added to make the + processing more clear. But this point has no drawbacks for + the user, it is just a fact which should be remembered: + Apache does more in the URL-to-filename hook than the API + intends for it.</li> + + <li> + Unbelievably mod_rewrite provides URL manipulations in + per-directory context, <em>i.e.</em>, within + <code>.htaccess</code> files, although these are reached + a very long time after the URLs have been translated to + filenames. It has to be this way because + <code>.htaccess</code> files live in the filesystem, so + processing has already reached this stage. In other + words: According to the API phases at this time it is too + late for any URL manipulations. To overcome this chicken + and egg problem mod_rewrite uses a trick: When you + manipulate a URL/filename in per-directory context + mod_rewrite first rewrites the filename back to its + corresponding URL (which is usually impossible, but see + the <code>RewriteBase</code> directive below for the + trick to achieve this) and then initiates a new internal + sub-request with the new URL. This restarts processing of + the API phases. + + <p>Again mod_rewrite tries hard to make this complicated + step totally transparent to the user, but you should + remember here: While URL manipulations in per-server + context are really fast and efficient, per-directory + rewrites are slow and inefficient due to this chicken and + egg problem. But on the other hand this is the only way + mod_rewrite can provide (locally restricted) URL + manipulations to the average user.</p> + </li> + </ol> + + <p>Don't forget these two points!</p> +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="InternalRuleset" id="InternalRuleset">Ruleset Processing</a></h2> + + <p>Now when mod_rewrite is triggered in these two API phases, it + reads the configured rulesets from its configuration + structure (which itself was either created on startup for + per-server context or during the directory walk of the Apache + kernel for per-directory context). Then the URL rewriting + engine is started with the contained ruleset (one or more + rules together with their conditions). The operation of the + URL rewriting engine itself is exactly the same for both + configuration contexts. Only the final result processing is + different. </p> + + <p>The order of rules in the ruleset is important because the + rewriting engine processes them in a special (and not very + obvious) order. The rule is this: The rewriting engine loops + through the ruleset rule by rule (<code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> directives) and + when a particular rule matches it optionally loops through + existing corresponding conditions (<code>RewriteCond</code> + directives). For historical reasons the conditions are given + first, and so the control flow is a little bit long-winded. See + Figure 1 for more details.</p> +<p class="figure"> + <img src="../images/mod_rewrite_fig1.gif" width="428" height="385" alt="[Needs graphics capability to display]" /><br /> + <dfn>Figure 1:</dfn>The control flow through the rewriting ruleset +</p> + <p>As you can see, first the URL is matched against the + <em>Pattern</em> of each rule. When it fails mod_rewrite + immediately stops processing this rule and continues with the + next rule. If the <em>Pattern</em> matches, mod_rewrite looks + for corresponding rule conditions. If none are present, it + just substitutes the URL with a new value which is + constructed from the string <em>Substitution</em> and goes on + with its rule-looping. But if conditions exist, it starts an + inner loop for processing them in the order that they are + listed. For conditions the logic is different: we don't match + a pattern against the current URL. Instead we first create a + string <em>TestString</em> by expanding variables, + back-references, map lookups, <em>etc.</em> and then we try + to match <em>CondPattern</em> against it. If the pattern + doesn't match, the complete set of conditions and the + corresponding rule fails. If the pattern matches, then the + next condition is processed until no more conditions are + available. If all conditions match, processing is continued + with the substitution of the URL with + <em>Substitution</em>.</p> + +</div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_tech.html" title="English"> en </a></p> +</div><div id="footer"> +<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> +</body></html>
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