Default Servlet Reference
Table of Contents
What is the DefaultServlet
The default servlet is the servlet which serves static resources as well as serves the directory listings (if directory listings are enabled).
Where is it declared?
It is declared globally in $CATALINA_BASE/conf/web.xml. By default here is it's declaration:
<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>What can I change?
The DefaultServlet allows the following initParamters:
| Property | Description |
|---|---|
debug | Debugging level. It is not very useful unless you are a tomcat developer. As of this writing, useful values are 0, 1, 11, 1000. [0] |
listings |
If no welcome file is present, can a directory listing be
shown?
value may be true or false [false]
Welcome files are part of the servlet api. WARNING: Listings of directories containing many entries are expensive. Multiple requests for large directory listings can consume significant proportions of server resources. |
precompressed |
If a precompressed version of a file exists (a file with .br
or .gz 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]
The precompressed file with the with .br or .gz
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.
It is also possible to configure the list of precompressed formats. The syntax is comma separated list of [content-encoding]=[file-extension] pairs. For example:
br=.br,gzip=.gz,bzip2=.bz2. 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.
|
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. |
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 contextXsltFile and localXsltFile below. The format of the xml is shown below. |
contextXsltFile |
You may also customize your directory listing by context by
configuring contextXsltFile. This must be a context
relative path (e.g.: /path/to/context.xslt) to a file with
a .xsl or .xslt extension. This overrides
globalXsltFile. If this value is present but a file does
not exist, then globalXsltFile will be used. If
globalXsltFile does not exist, then the default
directory listing will be shown.
|
localXsltFile |
You may also customize your directory listing by directory by
configuring localXsltFile. This must be a file in the
directory where the listing will take place to with a
.xsl or .xslt extension. This overrides
globalXsltFile and contextXsltFile. If this
value is present but a file does not exist, then
contextXsltFile will be used. If
contextXsltFile does not exist, then
globalXsltFile will be used. If
globalXsltFile does not exist, then the default
directory listing will be shown.
|
input | Input buffer size (in bytes) when reading resources to be served. [2048] |
output | Output buffer size (in bytes) when writing resources to be served. [2048] |
readonly | Is this context "read only", so HTTP commands like PUT and DELETE are rejected? [true] |
fileEncoding | File encoding to be used when reading static resources. [platform default] |
sendfileSize | 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] |
useAcceptRanges | If true, the Accept-Ranges header will be set when appropriate for the response. [true] |
showServerInfo | Should server information be presented in the response sent to clients when directory listing is enabled. [true] |
sortListings | Should the server sort the listings in a directory. [false] |
sortDirectoriesFirst | Should the server list all directories before all files. [false] |
How do I customize directory listings?
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)
You can use either localXsltFile or
globalXsltFile and DefaultServlet will create
an xml document and run it through an xsl transformation based
on the values provided in localXsltFile and
globalXsltFile. localXsltFile is first
checked, followed by globalXsltFile, then default
behaviors takes place.
Format:
<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>- size will be missing if
type='dir' - Readme is a CDATA entry
The following is a sample xsl file which mimics the default tomcat behavior:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="3.0">
<xsl:output method="html" html-version="5.0"
encoding="UTF-8" indent="no"
doctype-system="about:legacy-compat"/>
<xsl:template match="listing">
<html>
<head>
<title>
Sample Directory Listing For
<xsl:value-of select="@directory"/>
</title>
<style>
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; }
</style>
</head>
<body>
<h1>Sample Directory Listing For
<xsl:value-of select="@directory"/>
</h1>
<hr style="height: 1px;" />
<table style="width: 100%;">
<tr>
<th style="text-align: left;">Filename</th>
<th style="text-align: center;">Size</th>
<th style="text-align: right;">Last Modified</th>
</tr>
<xsl:apply-templates select="entries"/>
</table>
<xsl:apply-templates select="readme"/>
<hr style="height: 1px;" />
<h3>Apache Tomcat/<version-major-minor/></h3>
</body>
</html>
</xsl:template>
<xsl:template match="entries">
<xsl:apply-templates select="entry"/>
</xsl:template>
<xsl:template match="readme">
<hr style="height: 1px;" />
<pre><xsl:apply-templates/></pre>
</xsl:template>
<xsl:template match="entry">
<tr>
<td style="text-align: left;">
<xsl:variable name="urlPath" select="@urlPath"/>
<a href="{$urlPath}">
<pre><xsl:apply-templates/></pre>
</a>
</td>
<td style="text-align: right;">
<pre><xsl:value-of select="@size"/></pre>
</td>
<td style="text-align: right;">
<pre><xsl:value-of select="@date"/></pre>
</td>
</tr>
</xsl:template>
</xsl:stylesheet>How do I secure directory listings?
Use web.xml in each individual webapp. See the security section of the
Servlet specification.