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| <title>When not to use mod_rewrite - Apache HTTP Server Version 2.5</title> |
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| <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> |
| <p class="apache">Apache HTTP Server Version 2.5</p> |
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| <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> |
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| <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 2.5</a> > <a href="./">Rewrite</a></div><div id="page-content"><div id="preamble"><h1>When not to use mod_rewrite</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p> |
| </div> |
| |
| |
| <p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> |
| <a href="../mod/mod_rewrite.html">reference documentation</a>. It describes |
| perhaps one of the most important concepts about <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> - namely, |
| when to avoid using it.</p> |
| |
| <p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> should be considered a last resort, when other |
| alternatives are found wanting. Using it when there are simpler |
| alternatives leads to configurations which are confusing, fragile, and |
| hard to maintain. Understanding what other alternatives are available is |
| a very important step towards <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> mastery.</p> |
| |
| <p>Note that many of these examples won't work unchanged in your |
| particular server configuration, so it's important that you understand |
| them, rather than merely cutting and pasting the examples into your |
| configuration.</p> |
| |
| <p>The most common situation in which <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is |
| the right tool is when the very best solution requires access to the |
| server configuration files, and you don't have that access. Some |
| configuration directives are only available in the server configuration |
| file. So if you are in a hosting situation where you only have .htaccess |
| files to work with, you may need to resort to |
| <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p> |
| |
| </div> |
| <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#redirect">Simple Redirection</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#alias">URL Aliasing</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#vhosts">Virtual Hosting</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#proxy">Simple Proxying</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#setenv">Environment Variable Testing</a></li> |
| </ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module documentation</a></li><li><a href="intro.html">mod_rewrite introduction</a></li><li><a href="remapping.html">Redirection and remapping</a></li><li><a href="access.html">Controlling access</a></li><li><a href="vhosts.html">Virtual hosts</a></li><li><a href="proxy.html">Proxying</a></li><li><a href="rewritemap.html">Using RewriteMap</a></li><li><a href="advanced.html">Advanced techniques</a></li><li><a href="#comments_section">Comments</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="redirect" id="redirect">Simple Redirection</a></h2> |
| |
| |
| <p><code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> provides the <code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> and <code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directives, which provide a |
| means to redirect one URL to another. This kind of simple redirection of |
| one URL, or a class of URLs, to somewhere else, should be accomplished |
| using these directives rather than <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. <code>RedirectMatch</code> |
| allows you to include a regular expression in your redirection criteria, |
| providing many of the benefits of using <code>RewriteRule</code>.</p> |
| |
| <p>A common use for <code>RewriteRule</code> is to redirect an entire |
| class of URLs. For example, all URLs in the <code>/one</code> directory |
| must be redirected to <code>http://one.example.com/</code>, or perhaps |
| all <code>http</code> requests must be redirected to |
| <code>https</code>.</p> |
| |
| <p>These situations are better handled by the <code>Redirect</code> |
| directive. Remember that <code>Redirect</code> preserves path |
| information. That is to say, a redirect for a URL <code>/one</code> will |
| also redirect all URLs under that, such as <code>/one/two.html</code> |
| and <code>/one/three/four.html</code>.</p> |
| |
| <p>To redirect URLs under <code>/one</code> to |
| <code>http://one.example.com</code>, do the following:</p> |
| |
| <pre class="prettyprint lang-config">Redirect "/one/" "http://one.example.com/"</pre> |
| |
| |
| <p>To redirect one hostname to another, for example |
| <code>example.com</code> to <code>www.example.com</code>, see the |
| <a href="remapping.html#canonicalhost">Canonical Hostnames</a> |
| recipe.</p> |
| |
| <p>To redirect <code>http</code> URLs to <code>https</code>, do the |
| following:</p> |
| |
| <pre class="prettyprint lang-config"><VirtualHost *:80> |
| ServerName www.example.com |
| Redirect "/" "https://www.example.com/" |
| </VirtualHost> |
| |
| <VirtualHost *:443> |
| ServerName www.example.com |
| # ... SSL configuration goes here |
| </VirtualHost></pre> |
| |
| |
| <p>The use of <code>RewriteRule</code> to perform this task may be |
| appropriate if there are other <code>RewriteRule</code> directives in |
| the same scope. This is because, when there are <code>Redirect</code> |
| and <code>RewriteRule</code> directives in the same scope, the |
| <code>RewriteRule</code> directives will run first, regardless of the |
| order of appearance in the configuration file.</p> |
| |
| <p>In the case of the <em>http-to-https</em> redirection, the use of |
| <code>RewriteRule</code> would be appropriate if you don't have access |
| to the main server configuration file, and are obliged to perform this |
| task in a <code>.htaccess</code> file instead.</p> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="alias" id="alias">URL Aliasing</a></h2> |
| <p>The <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> directive |
| provides mapping from a URI to a directory - usually a directory outside |
| of your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>. Although it |
| is possible to perform this mapping with <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>, |
| <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> is the preferred method, for |
| reasons of simplicity and performance.</p> |
| |
| <div class="example"><h3>Using Alias</h3><pre class="prettyprint lang-config">Alias "/cats" "/var/www/virtualhosts/felines/htdocs"</pre> |
| </div> |
| |
| <p> |
| The use of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> to perform this mapping may be |
| appropriate when you do not have access to the server configuration |
| files. Alias may only be used in server or virtualhost context, and not |
| in a <code>.htaccess</code> file. |
| </p> |
| |
| <p>Symbolic links would be another way to accomplish the same thing, if |
| you have <code>Options FollowSymLinks</code> enabled on your |
| server.</p> |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="vhosts" id="vhosts">Virtual Hosting</a></h2> |
| <p>Although it is possible to handle <a href="vhosts.html">virtual hosts |
| with mod_rewrite</a>, it is seldom the right way. Creating individual |
| <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> blocks is |
| almost always the right way to go. In the |
| event that you have an enormous number of virtual hosts, consider using |
| <code class="module"><a href="../mod/mod_vhost_alias.html">mod_vhost_alias</a></code> to create these hosts automatically.</p> |
| |
| <p>Modules such as <code class="module"><a href="../mod/mod_macro.html">mod_macro</a></code> are |
| also useful for creating a large number of virtual hosts dynamically.</p> |
| |
| <p>Using <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> for vitualhost creation may be |
| appropriate if you are using a hosting service that does not provide |
| you access to the server configuration files, and you are therefore |
| restricted to configuration using <code>.htaccess</code> files.</p> |
| |
| <p>See the <a href="vhosts.html">virtual hosts with mod_rewrite</a> |
| document for more details on how you might accomplish this if it still |
| seems like the right approach.</p> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="proxy" id="proxy">Simple Proxying</a></h2> |
| |
| <p><code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> provides the <a href="flags.html#flag_p">[P]</a> flag to pass rewritten URIs through |
| <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>.</p> |
| |
| <pre class="prettyprint lang-config">RewriteRule "^/?images(.*)" "http://imageserver.local/images$1" [P]</pre> |
| |
| |
| <p>However, in many cases, when there is no actual pattern matching |
| needed, as in the example shown above, the <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> directive is a better choice. |
| The example here could be rendered as:</p> |
| |
| <pre class="prettyprint lang-config">ProxyPass "/images/" "http://imageserver.local/images/"</pre> |
| |
| |
| <p>Note that whether you use <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> or <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>, you'll still need to use the |
| <code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code> directive to |
| catch redirects issued from the back-end server:</p> |
| |
| <pre class="prettyprint lang-config">ProxyPassReverse "/images/" "http://imageserver.local/images/"</pre> |
| |
| |
| <p>You may need to use <code>RewriteRule</code> instead when there are |
| other <code>RewriteRule</code>s in effect in the same scope, as a |
| <code>RewriteRule</code> will usually take effect before a |
| <code>ProxyPass</code>, and so may preempt what you're trying to |
| accomplish.</p> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="setenv" id="setenv">Environment Variable Testing</a></h2> |
| |
| <p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is frequently used to take a particular |
| action based on the presence or absence of a particular environment |
| variable or request header. This can be done more efficiently using the |
| <code class="directive"><a href="../mod/core.html#if"><If></a></code>.</p> |
| |
| <p>Consider, for example, the common scenario where |
| <code class="directive">RewriteRule</code> is used to enforce a canonical |
| hostname, such as <code>www.example.com</code> instead of |
| <code>example.com</code>. This can be done using the <code class="directive"><a href="../mod/core.html#if"><If></a></code> directive, as shown here:</p> |
| |
| <pre class="prettyprint lang-config"><If "req('Host') != 'www.example.com'"> |
| Redirect "/" "http://www.example.com/" |
| </If></pre> |
| |
| |
| <p>This technique can be used to take actions based on any request |
| header, response header, or environment variable, replacing |
| <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> in many common scenarios.</p> |
| |
| <p>See especially the <a href="../expr.html">expression evaluation |
| documentation</a> for a overview of what types of expressions you can |
| use in <code class="directive"><a href="../mod/core.html#if"><If></a></code> sections, |
| and in certain other directives.</p> |
| |
| </div></div> |
| <div class="bottomlang"> |
| <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p> |
| </div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div> |
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