# Apache Tomcat 6.0

## Default Servlet Reference

Introduction

> This discusses different ways to manipulate the default servlet. Topics are
> - What is the DefaultServlet?
> - Where is it declared?
> - What can I change?
> - How do I customize directory listings?
> - How do I secure directory listings?

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>true</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>

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

What can I change?

> The DefaultServlet allows the following initParamters:

> 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.
> listings | If no welcome file is present, can a directory listing be shown? value may be true or 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.
> 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. default value is null
> globalXsltFile | 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.

> localXsltFile

> You may also customize your directory listing by directory by configuring `localXsltFile`. This should be a relative file name in the directory where the listing will take place. 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.

> 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]

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 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)

> 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"?>

>     <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>       version="1.0">

>       <xsl:output method="xhtml" encoding="iso-8859-1" indent="no"/>

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

>       <xsl:template match="entries">
>         <xsl:apply-templates select="entry"/>
>       </xsl:template>

>       <xsl:template match="readme">
>         <hr size="1" />
>         <pre><xsl:apply-templates/></pre>
>       </xsl:template>

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

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