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10 <title>mod_xml2enc - Apache HTTP Server Version 2.5</title>
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21 <p class="apache">Apache HTTP Server Version 2.5</p>
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25 <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="./">Modules</a></div>
26 <div id="page-content">
27 <div id="preamble"><h1>Apache Module mod_xml2enc</h1>
29 <p><span>Available Languages: </span><a href="../en/mod/mod_xml2enc.html" title="English"> en </a></p>
31 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Enhanced charset/internationalisation support for libxml2-based
32 filter modules</td></tr>
33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>xml2enc_module</td></tr>
35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_xml2enc.c</td></tr>
36 <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.4 and later. Available as a third-party module
37 for 2.2.x versions</td></tr></table>
40 <p>This module provides enhanced internationalisation support for
41 markup-aware filter modules such as <code class="module"><a href="../mod/mod_proxy_html.html">mod_proxy_html</a></code>.
42 It can automatically detect the encoding of input data and ensure
43 they are correctly processed by the <a href="http://xmlsoft.org/">libxml2</a> parser, including converting to Unicode (UTF-8) where
44 necessary. It can also convert data to an encoding of choice
45 after markup processing, and will ensure the correct <var>charset</var>
46 value is set in the HTTP <var>Content-Type</var> header.</p>
48 <div id="quickview"><h3>Topics</h3>
50 <li><img alt="" src="../images/down.gif" /> <a href="#usage">Usage</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#api">Programming API</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#sniffing">Detecting an Encoding</a></li>
53 <li><img alt="" src="../images/down.gif" /> <a href="#output">Output Encoding</a></li>
54 <li><img alt="" src="../images/down.gif" /> <a href="#alias">Unsupported Encodings</a></li>
55 </ul><h3 class="directives">Directives</h3>
57 <li><img alt="" src="../images/down.gif" /> <a href="#xml2encalias">xml2EncAlias</a></li>
58 <li><img alt="" src="../images/down.gif" /> <a href="#xml2encdefault">xml2EncDefault</a></li>
59 <li><img alt="" src="../images/down.gif" /> <a href="#xml2startparse">xml2StartParse</a></li>
61 <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_xml2enc">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_xml2enc">Report a bug</a></li></ul><h3>See also</h3>
63 <li><a href="#comments_section">Comments</a></li></ul></div>
64 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
66 <h2><a name="usage" id="usage">Usage</a></h2>
67 <p>There are two usage scenarios: with modules programmed to work
68 with mod_xml2enc, and with those that are not aware of it:</p>
70 <dt>Filter modules enabled for mod_xml2enc</dt><dd>
71 <p>Modules such as <code class="module"><a href="../mod/mod_proxy_html.html">mod_proxy_html</a></code> version 3.1
72 and up use the <code>xml2enc_charset</code> optional function to retrieve
73 the charset argument to pass to the libxml2 parser, and may use the
74 <code>xml2enc_filter</code> optional function to postprocess to another
75 encoding. Using mod_xml2enc with an enabled module, no configuration
76 is necessary: the other module will configure mod_xml2enc for you
77 (though you may still want to customise it using the configuration
78 directives below).</p>
80 <dt>Non-enabled modules</dt><dd>
81 <p>To use it with a libxml2-based module that isn't explicitly enabled for
82 mod_xml2enc, you will have to configure the filter chain yourself.
83 So to use it with a filter foo provided by a module mod_foo to
84 improve the latter's i18n support with HTML and XML, you could use</p>
86 FilterProvider iconv xml2enc Content-Type $text/html
87 FilterProvider iconv xml2enc Content-Type $xml
88 FilterProvider markup foo Content-Type $text/html
89 FilterProvider markup foo Content-Type $xml
90 FilterChain iconv markup
92 <p>mod_foo will now support any character set supported by either
93 (or both) of libxml2 or apr_xlate/iconv.</p>
95 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
97 <h2><a name="api" id="api">Programming API</a></h2>
98 <p>Programmers writing libxml2-based filter modules are encouraged to
99 enable them for mod_xml2enc, to provide strong i18n support for your
100 users without reinventing the wheel. The programming API is exposed in
101 <var>mod_xml2enc.h</var>, and a usage example is
102 <code class="module"><a href="../mod/mod_proxy_html.html">mod_proxy_html</a></code>.</p>
103 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
104 <div class="section">
105 <h2><a name="sniffing" id="sniffing">Detecting an Encoding</a></h2>
106 <p>Unlike <code class="module"><a href="../mod/mod_charset_lite.html">mod_charset_lite</a></code>, mod_xml2enc is designed
107 to work with data whose encoding cannot be known in advance and thus
108 configured. It therefore uses 'sniffing' techniques to detect the
109 encoding of HTTP data as follows:</p>
111 <li>If the HTTP <var>Content-Type</var> header includes a
112 <var>charset</var> parameter, that is used.</li>
113 <li>If the data start with an XML Byte Order Mark (BOM) or an
114 XML encoding declaration, that is used.</li>
115 <li>If an encoding is declared in an HTML <code><META></code>
116 element, that is used.</li>
117 <li>If none of the above match, the default value set by
118 <code class="directive">xml2EncDefault</code> is used.</li>
120 <p>The rules are applied in order. As soon as a match is found,
121 it is used and detection is stopped.</p>
122 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
123 <div class="section">
124 <h2><a name="output" id="output">Output Encoding</a></h2>
125 <p><a href="http://xmlsoft.org/">libxml2</a> always uses UTF-8 (Unicode)
126 internally, and libxml2-based filter modules will output that by default.
127 mod_xml2enc can change the output encoding through the API, but there
128 is currently no way to configure that directly.</p>
129 <p>Changing the output encoding should (in theory, at least) never be
130 necessary, and is not recommended due to the extra processing load on
131 the server of an unnecessary conversion.</p>
132 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
133 <div class="section">
134 <h2><a name="alias" id="alias">Unsupported Encodings</a></h2>
135 <p>If you are working with encodings that are not supported by any of
136 the conversion methods available on your platform, you can still alias
137 them to a supported encoding using <code class="directive">xml2EncAlias</code>.</p>
139 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
140 <div class="directive-section"><h2><a name="xml2EncAlias" id="xml2EncAlias">xml2EncAlias</a> <a name="xml2encalias" id="xml2encalias">Directive</a></h2>
141 <table class="directive">
142 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Recognise Aliases for encoding values</td></tr>
143 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>xml2EncAlias <var>charset alias [alias ...]</var></code></td></tr>
144 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
145 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
146 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_xml2enc</td></tr>
148 <p>This server-wide directive aliases one or more encoding to another
149 encoding. This enables encodings not recognised by libxml2 to be handled
150 internally by libxml2's encoding support using the translation table for
151 a recognised encoding. This serves two purposes: to support character sets
152 (or names) not recognised either by libxml2 or iconv, and to skip
153 conversion for an encoding where it is known to be unnecessary.</p>
156 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
157 <div class="directive-section"><h2><a name="xml2EncDefault" id="xml2EncDefault">xml2EncDefault</a> <a name="xml2encdefault" id="xml2encdefault">Directive</a></h2>
158 <table class="directive">
159 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets a default encoding to assume when absolutely no information
160 can be <a href="#sniffing">automatically detected</a></td></tr>
161 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>xml2EncDefault <var>name</var></code></td></tr>
162 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
163 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
164 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_xml2enc</td></tr>
165 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.4.0 and later; available as a third-party
166 module for earlier versions.</td></tr>
168 <p>If you are processing data with known encoding but no encoding
169 information, you can set this default to help mod_xml2enc process
170 the data correctly. For example, to work with the default value
171 of Latin1 (<var>iso-8859-1</var> specified in HTTP/1.0, use</p>
172 <pre class="prettyprint lang-config">xml2EncDefault iso-8859-1</pre>
176 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
177 <div class="directive-section"><h2><a name="xml2StartParse" id="xml2StartParse">xml2StartParse</a> <a name="xml2startparse" id="xml2startparse">Directive</a></h2>
178 <table class="directive">
179 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Advise the parser to skip leading junk.</td></tr>
180 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>xml2StartParse <var>element [element ...]</var></code></td></tr>
181 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
182 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
183 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_xml2enc</td></tr>
185 <p>Specify that the markup parser should start at the first instance
186 of any of the elements specified. This can be used as a workaround
187 where a broken backend inserts leading junk that messes up the parser (<a href="http://bahumbug.wordpress.com/2006/10/12/mod_proxy_html-revisited/">example here</a>).</p>
188 <p>It should never be used for XML, nor well-formed HTML.</p>
192 <div class="bottomlang">
193 <p><span>Available Languages: </span><a href="../en/mod/mod_xml2enc.html" title="English"> en </a></p>
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