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_HOME/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:
Attribute | Description |
debug |
Debugging level. It is not very useful unless you are a JBoss Web 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
|
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. The 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 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 |
localXsltFile |
You may also customize your directory listing by directory by
configuring |
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] |
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
<?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>JBoss Web/2.1</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>