<?xml version="1.0"?>
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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="Introduction">

This discusses different ways to manipulate the default servlet. Topics are
<ul>
  <li><a href="#what">What is the DefaultServlet?</a></li>
  <li><a href="#where">Where is it declared?</a></li>
  <li><a href="#change">What can I change?</a></li>
  <li><a href="#dir">How do I customize directory listings?</a></li>
  <li><a href="#secure">How do I secure directory listings?</a></li>

</ul>

</section>

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

</section>

<section name="Where is it declared?">
<a name="where"></a>
It is declared globally in <i>$CATALINA_HOME/conf/web.xml</i>.
By default here is it's declaration:
<source>
    &lt;servlet&gt;
        &lt;servlet-name&gt;default&lt;/servlet-name&gt;
        &lt;servlet-class&gt;
          org.apache.catalina.servlets.DefaultServlet
        &lt;/servlet-class&gt;
        &lt;init-param&gt;
            &lt;param-name&gt;debug&lt;/param-name&gt;
            &lt;param-value&gt;0&lt;/param-value&gt;
        &lt;/init-param&gt;
        &lt;init-param&gt;
            &lt;param-name&gt;listings&lt;/param-name&gt;
            &lt;param-value&gt;true&lt;/param-value&gt;
        &lt;/init-param&gt;
        &lt;load-on-startup&gt;1&lt;/load-on-startup&gt;
    &lt;/servlet&gt;

...

    &lt;servlet-mapping&gt;
        &lt;servlet-name&gt;default&lt;/servlet-name&gt;
        &lt;url-pattern&gt;/&lt;/url-pattern&gt;
    &lt;/servlet-mapping&gt;

</source>

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

<section name="What can I change?">
<a name="change"></a>
The DefaultServlet allows the following initParamters:

<table border="1">
  <tr>
    <th valign='top'>debug</th>
    <td valign='top'>
        Debugging level. It is not very useful unless you are a tomcat
        developer. As
        of this writing, useful values are 0, 1, 11, 1000.
    </td>
  </tr>
  <tr>
    <th valign='top'>listings</th>
    <td valign='top'>
        If no welcome file is present, can a directory listing be
        shown?
        value may be <b>true</b> or <b>false</b>
        <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.
    </td>
  </tr>
  <tr>
    <th valign='top'>readmeFile</th>
    <td valign='top'>
        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. default value is null
    </td>
  </tr>
  <tr>
    <th valign='top'>globalXsltFile</th>
    <td valign='top'>
        If you wish to customize your directory listing, you
        can use an XSL transformation. This value is an absolute
        file name which be used for all direcotory listings.
        This can be disabled by per webapp by also declaring the
        default servlet in your local webapp's web.xml. The format
        of the xml is shown below.
    </td>
  </tr>
  <tr>
    <th valign='top'>localXsltFile</th>
    <td valign='top'>
        You may also customize your directory listing by directory by
        configuring <code>localXsltFile</code>. This should be a relative
        file name in the directory where the listing will take place.
        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.
    </td>
  </tr>
  <tr>
    <th valign='top'>input</th>
    <td valign='top'>
        Input buffer size (in bytes) when reading
        resources to be served.  [2048]
    </td>
  </tr>
  <tr>
    <th valign='top'>output</th>
    <td valign='top'>
        Output buffer size (in bytes) when writing
        resources to be served.  [2048]
    </td>
  </tr>
  <tr>
    <th valign='top'>readonly</th>
    <td valign='top'>
        Is this context "read only", so HTTP commands like PUT and
        DELETE are rejected?  [true]
    </td>
  </tr>
  <tr>
    <th valign='top'>fileEncoding</th>
    <td valign='top'>
        File encoding to be used when reading static resources.
        [platform default]
    </td>
  </tr>
  <tr>
    <th valign='top'>sendfileSize</th>
    <td valign='top'>
        If the connector used supports sendfile, this represents the minimal 
        file size in KB for which sendfile will be used. Use a negative value 
        to always disable sendfile. [48]
    </td>
  </tr>

</table>
</section>

<section name="How do I customize directory listings?">
<a name="dir"></a>
<p>You can override DefaultServlet with you own implementation and use that
in your web.xml declaration. If you
can undertand what was just said, we will assume yo 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> or
<code>globalXsltFile</code> and DefaultServlet will create
an xml document and run it through an xsl transformation based
on the values provided in <code>localXsltFile</code> and
<code>globalXsltFile</code>. <code>localXsltFile</code> is first
checked, followed by <code>globalXsltFile</code>, then default
behaviors takes place.
</p>

<p>
Format:
<source>
    &lt;listing&gt;
     &lt;entries&gt;
      &lt;entry type='file|dir' urlPath='aPath' size='###' date='gmt date'&gt;
        fileName1
      &lt;/entry&gt;
      &lt;entry type='file|dir' urlPath='aPath' size='###' date='gmt date'&gt;
        fileName2
      &lt;/entry&gt;
      ...
     &lt;/entries&gt;
     &lt;readme&gt;&lt;/readme&gt;
    &lt;/listing&gt;
</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:
<source>
&lt;?xml version="1.0"?&gt;

&lt;xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  version="1.0"&gt;

  &lt;xsl:output method="xhtml" encoding="iso-8859-1" indent="no"/&gt;

  &lt;xsl:template match="listing"&gt;
   &lt;html&gt;
    &lt;head&gt;
      &lt;title&gt;
        Sample Directory Listing For
        &lt;xsl:value-of select="@directory"/&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;}
      &lt;/style&gt;
    &lt;/head&gt;
    &lt;body&gt;
      &lt;h1&gt;Sample Directory Listing For
            &lt;xsl:value-of select="@directory"/&gt;
      &lt;/h1&gt;
      &lt;hr size="1" /&gt;
      &lt;table cellspacing="0"
                  width="100%"
            cellpadding="5"
                  align="center"&gt;
        &lt;tr&gt;
          &lt;th align="left"&gt;Filename&lt;/th&gt;
          &lt;th align="center"&gt;Size&lt;/th&gt;
          &lt;th align="right"&gt;Last Modified&lt;/th&gt;
        &lt;/tr&gt;
        &lt;xsl:apply-templates select="entries"/&gt;
        &lt;/table&gt;
      &lt;xsl:apply-templates select="readme"/&gt;
      &lt;hr size="1" /&gt;
      &lt;h3&gt;Apache Tomcat/6.0&lt;/h3&gt;
    &lt;/body&gt;
   &lt;/html&gt;
  &lt;/xsl:template&gt;


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

  &lt;xsl:template match="readme"&gt;
    &lt;hr size="1" /&gt;
    &lt;pre&gt;&lt;xsl:apply-templates/&gt;&lt;/pre&gt;
  &lt;/xsl:template&gt;

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

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

</section>

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

</section>

</body>

</document>
