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<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="default-servlet.html">

    &project;

    <properties>
        <author email="funkman@apache.org">Tim Funk</author>
        <title>Default Servlet Reference</title>
    </properties>

<body>

<section name="Table of Contents">
<toc/>
</section>

<section anchor="what" name="What is the DefaultServlet">
<p>
The default servlet is the servlet which serves static resources as well
as serves the directory listings (if directory listings are enabled).
</p>
</section>

<section anchor="where" name="Where is it declared?">
<p>
It is declared globally in <i>$CATALINA_BASE/conf/web.xml</i>.
By default here is it's declaration:
</p>
<source><![CDATA[    <servlet>
        <servlet-name>default</servlet-name>
        <servlet-class>
          org.apache.catalina.servlets.DefaultServlet
        </servlet-class>
        <init-param>
            <param-name>debug</param-name>
            <param-value>0</param-value>
        </init-param>
        <init-param>
            <param-name>listings</param-name>
            <param-value>false</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

...

    <servlet-mapping>
        <servlet-name>default</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>]]></source>

<p>So by default, the default servlet is loaded at webapp startup and directory
listings are disabled and debugging is turned off.</p>

<p>If you need to change the DefaultServlet settings for an application you can
override the default configuration by re-defining the DefaultServlet in
<code>/WEB-INF/web.xml</code>. However, this will cause problems if you attempt
to deploy the application on another container as the DefaultServlet class will
not be recognised. You can work-around this problem by using the Tomcat specific
<code>/WEB-INF/tomcat-web.xml</code> deployment descriptor. The format is
identical to <code>/WEB-INF/web.xml</code>. It will override any default
settings but not those in <code>/WEB-INF/web.xml</code>. Since it is Tomcat
specific, it will only be processed when the application is deployed on
Tomcat.</p>
</section>

<section anchor="change" name="What can I change?">
<p>
  The DefaultServlet allows the following initParameters:
</p>

<properties>
  <property name="debug">
        Debugging level. It is not very useful unless you are a tomcat
        developer. As
        of this writing, useful values are 0, 1, 11. [0]
  </property>
  <property name="listings">
        If no welcome file is present, can a directory listing be
        shown?
        value may be <b>true</b> or <b>false</b> [false]
        <br />
        Welcome files are part of the servlet api.
        <br />
        <b>WARNING:</b> Listings of directories containing many entries are
        expensive. Multiple requests for large directory listings can consume
        significant proportions of server resources.
  </property>
  <property name="precompressed">
        If a precompressed version of a file exists (a file with <code>.br</code>
        or <code>.gz</code> appended to the file name located alongside the
        original file), Tomcat will serve the precompressed file if the user
        agent supports the matching content encoding (br or gzip) and this
        option is enabled. [false]
        <br />
        The precompressed file with the with <code>.br</code> or <code>.gz</code>
        extension will be accessible if requested directly so if the original
        resource is protected with a security constraint, the precompressed
        versions must be similarly protected.
        <br />
        It is also possible to configure the list of precompressed formats.
        The syntax is comma separated list of
        <code>[content-encoding]=[file-extension]</code> pairs. For example:
        <code>br=.br,gzip=.gz,bzip2=.bz2</code>. If multiple formats are
        specified, the client supports more than one and the client does not
        express a preference, the order of the list of formats will be treated
        as the server preference order and used to select the format returned.
  </property>
  <property name="readmeFile">
        If a directory listing is presented, a readme file may also
        be presented with the listing. This file is inserted as is
        so it may contain HTML.
  </property>
  <property name="globalXsltFile">
        If you wish to customize your directory listing, you
        can use an XSL transformation. This value is a relative file name (to
        either $CATALINA_BASE/conf/ or $CATALINA_HOME/conf/) which will be used
        for all directory listings. This can be overridden per context and/or
        per directory. See <strong>contextXsltFile</strong> and
        <strong>localXsltFile</strong> below. The format of the xml is shown
        below.
  </property>
  <property name="contextXsltFile">
        You may also customize your directory listing by context by
        configuring <code>contextXsltFile</code>. This must be a context
        relative path (e.g.: <code>/path/to/context.xslt</code>) to a file with
        a <code>.xsl</code> or <code>.xslt</code> extension. This overrides
        <code>globalXsltFile</code>. If this value is present but a file does
        not exist, then <code>globalXsltFile</code> will be used. If
        <code>globalXsltFile</code> does not exist, then the default
        directory listing will be shown.
  </property>
  <property name="localXsltFile">
        You may also customize your directory listing by directory by
        configuring <code>localXsltFile</code>. This must be a file in the
        directory where the listing will take place to with a
        <code>.xsl</code> or <code>.xslt</code> extension. This overrides
        <code>globalXsltFile</code> and <code>contextXsltFile</code>. If this
        value is present but a file does not exist, then
        <code>contextXsltFile</code> will be used. If
        <code>contextXsltFile</code> does not exist, then
        <code>globalXsltFile</code> will be used. If
        <code>globalXsltFile</code> does not exist, then the default
        directory listing will be shown.
  </property>
  <property name="input">
        Input buffer size (in bytes) when reading
        resources to be served.  [2048]
  </property>
  <property name="output">
        Output buffer size (in bytes) when writing
        resources to be served.  [2048]
  </property>
  <property name="readonly">
        Is this context "read only", so HTTP commands like PUT and
        DELETE are rejected?  [true]
  </property>
  <property name="fileEncoding">
        File encoding to be used when reading static resources.
        [platform default]
  </property>
  <property name="useBomIfPresent">
        If a static file contains a byte order mark (BOM), should this be used
        to determine the file encoding in preference to fileEncoding. This
        setting must be one of <code>true</code> (remove the BOM and use it in
        preference to fileEncoding), <code>false</code> (remove the BOM but do
        not use it) or <code>pass-through</code> (do not use the BOM and do not
        remove it). [true]
  </property>
  <property name="sendfileSize">
        If the connector used supports sendfile, this represents the minimal
        file size in KiB for which sendfile will be used. Use a negative value
        to always disable sendfile. [48]
  </property>
  <property name="useAcceptRanges">
        If true, the Accept-Ranges header will be set when appropriate for the
        response. [true]
        <br/>
        Deprecated. This option will be removed without replacement in Tomcat
        12 onwards where it will effectively be hard coded to <code>true</code>.
  </property>
  <property name="showServerInfo">
        Should server information be presented in the response sent to clients
        when directory listing is enabled. [true]
  </property>
  <property name="sortListings">
        Should the server sort the listings in a directory. [false]
  </property>
  <property name="sortDirectoriesFirst">
        Should the server list all directories before all files. [false]
  </property>
  <property name="allowPartialPut">
        Should the server treat an HTTP PUT request with a Content-Range header
        as a partial PUT? Note that while RFC 7231 clarified that such a PUT
        with a Content-Range header field is a bad request, RFC 9110
        (which obsoletes RFC 7231) now allows partial PUT. [true]
  </property>
  <property name="directoryRedirectStatusCode">
        When a directory redirect (trailing slash missing) is made, use this as
        the HTTP response code. [302]
  </property>
  <property name="allowPostAsGet">
        Controls whether a direct request (i.e. not a forward or an include) for
        a static resource using the POST method will be processed as if the GET
        method had been used. If not allowed, the request will be rejected. The
        default behaviour of processing the request as if the GET method had
        been used is unchanged. [true]
  </property>
</properties>
</section>

<section anchor="dir" name="How do I customize directory listings?">
<p>You can override DefaultServlet with you own implementation and use that
in your web.xml declaration. If you
can understand what was just said, we will assume you can read the code
to DefaultServlet servlet and make the appropriate adjustments. (If not,
then that method isn't for you)
</p>
<p>
You can use either  <code>localXsltFile</code>, <code>contextXsltFile</code>
or <code>globalXsltFile</code> and DefaultServlet will create
an xml document and run it through an xsl transformation based
on the values provided in the XSLT file. <code>localXsltFile</code> is first
checked, then <code>contextXsltFile</code>, followed by
<code>globalXsltFile</code>. If no XSLT files are configured, default behavior
is used.
</p>

<p>
Format:
</p>
<source><![CDATA[    <listing>
     <entries>
      <entry type='file|dir' urlPath='aPath' size='###' date='gmt date'>
        fileName1
      </entry>
      <entry type='file|dir' urlPath='aPath' size='###' date='gmt date'>
        fileName2
      </entry>
      ...
     </entries>
     <readme></readme>
    </listing>]]></source>
<ul>
  <li>size will be missing if <code>type='dir'</code></li>
  <li>Readme is a CDATA entry</li>
</ul>

<p>
  The following is a sample xsl file which mimics the default tomcat behavior:
</p>
<source>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;

&lt;xsl:stylesheet xmlns:xsl=&quot;http://www.w3.org/1999/XSL/Transform&quot;
  version=&quot;3.0&quot;&gt;

  &lt;xsl:output method=&quot;html&quot; html-version=&quot;5.0&quot;
    encoding=&quot;UTF-8&quot; indent=&quot;no&quot;
    doctype-system=&quot;about:legacy-compat&quot;/&gt;

  &lt;xsl:template match=&quot;listing&quot;&gt;
   &lt;html&gt;
    &lt;head&gt;
      &lt;title&gt;
        Sample Directory Listing For
        &lt;xsl:value-of select=&quot;@directory&quot;/&gt;
      &lt;/title&gt;
      &lt;style&gt;
        h1 {color : white;background-color : #0086b2;}
        h3 {color : white;background-color : #0086b2;}
        body {font-family : sans-serif,Arial,Tahoma;
             color : black;background-color : white;}
        b {color : white;background-color : #0086b2;}
        a {color : black;} HR{color : #0086b2;}
        table td { padding: 5px; }
      &lt;/style&gt;
    &lt;/head&gt;
    &lt;body&gt;
      &lt;h1&gt;Sample Directory Listing For
            &lt;xsl:value-of select=&quot;@directory&quot;/&gt;
      &lt;/h1&gt;
      &lt;hr style=&quot;height: 1px;&quot; /&gt;
      &lt;table style=&quot;width: 100%;&quot;&gt;
        &lt;tr&gt;
          &lt;th style=&quot;text-align: left;&quot;&gt;Filename&lt;/th&gt;
          &lt;th style=&quot;text-align: center;&quot;&gt;Size&lt;/th&gt;
          &lt;th style=&quot;text-align: right;&quot;&gt;Last Modified&lt;/th&gt;
        &lt;/tr&gt;
        &lt;xsl:apply-templates select=&quot;entries&quot;/&gt;
        &lt;/table&gt;
      &lt;xsl:apply-templates select=&quot;readme&quot;/&gt;
      &lt;hr style=&quot;height: 1px;&quot; /&gt;
      &lt;h3&gt;Apache Tomcat/<version-major-minor/>&lt;/h3&gt;
    &lt;/body&gt;
   &lt;/html&gt;
  &lt;/xsl:template&gt;


  &lt;xsl:template match=&quot;entries&quot;&gt;
    &lt;xsl:apply-templates select=&quot;entry&quot;/&gt;
  &lt;/xsl:template&gt;

  &lt;xsl:template match=&quot;readme&quot;&gt;
    &lt;hr style=&quot;height: 1px;&quot; /&gt;
    &lt;pre&gt;&lt;xsl:apply-templates/&gt;&lt;/pre&gt;
  &lt;/xsl:template&gt;

  &lt;xsl:template match=&quot;entry&quot;&gt;
    &lt;tr&gt;
      &lt;td style=&quot;text-align: left;&quot;&gt;
        &lt;xsl:variable name=&quot;urlPath&quot; select=&quot;@urlPath&quot;/&gt;
        &lt;a href=&quot;{$urlPath}&quot;&gt;
          &lt;pre&gt;&lt;xsl:apply-templates/&gt;&lt;/pre&gt;
        &lt;/a&gt;
      &lt;/td&gt;
      &lt;td style=&quot;text-align: right;&quot;&gt;
        &lt;pre&gt;&lt;xsl:value-of select=&quot;@size&quot;/&gt;&lt;/pre&gt;
      &lt;/td&gt;
      &lt;td style=&quot;text-align: right;&quot;&gt;
        &lt;pre&gt;&lt;xsl:value-of select=&quot;@date&quot;/&gt;&lt;/pre&gt;
      &lt;/td&gt;
    &lt;/tr&gt;
  &lt;/xsl:template&gt;

&lt;/xsl:stylesheet&gt;</source>

</section>

<section anchor="secure" name="How do I secure directory listings?">
Use web.xml in each individual webapp. See the security section of the
Servlet specification.

</section>

</body>

</document>
