Apache Tomcat 8

• Introduction
• Installation
• Servlet Configuration
• Filter Configuration
• Directives
• Variables

SSI (Server Side Includes) are directives that are placed in HTML pages, and evaluated on the server while the pages are being served. They let you add dynamically generated content to an existing HTML page, without having to serve the entire page via a CGI program, or other dynamic technology.

Within Tomcat SSI support can be added when using Tomcat as your HTTP server and you require SSI support. Typically this is done during development when you don't want to run a web server like Apache.

Tomcat SSI support implements the same SSI directives as Apache. See the Apache Introduction to SSI for information on using SSI directives.

SSI support is available as a servlet and as a filter. You should use one or the other to provide SSI support but not both.

Servlet based SSI support is implemented using the class org.apache.catalina.ssi.SSIServlet. Traditionally, this servlet is mapped to the URL pattern "*.shtml".

Filter based SSI support is implemented using the class org.apache.catalina.ssi.SSIFilter. Traditionally, this filter is mapped to the URL pattern "*.shtml", though it can be mapped to "*" as it will selectively enable/disable SSI processing based on mime types. The contentType init param allows you to apply SSI processing to JSP pages, javascript, or any other content you wish.

By default SSI support is disabled in Tomcat.

CAUTION - SSI directives can be used to execute programs external to the Tomcat JVM. If you are using the Java SecurityManager this will bypass your security policy configuration in catalina.policy.

To use the SSI servlet, remove the XML comments from around the SSI servlet and servlet-mapping configuration in $CATALINA_BASE/conf/web.xml.

To use the SSI filter, remove the XML comments from around the SSI filter and filter-mapping configuration in $CATALINA_BASE/conf/web.xml.

Only Contexts which are marked as privileged may use SSI features (see the privileged property of the Context element).

There are several servlet init parameters which can be used to configure the behaviour of the SSI servlet.

• buffered - Should output from this servlet be buffered? (0=false, 1=true) Default 0 (false).
• debug - Debugging detail level for messages logged by this servlet. Default 0.
• expires - The number of seconds before a page with SSI directives will expire. Default behaviour is for all SSI directives to be evaluated for every request.
• isVirtualWebappRelative - Should "virtual" SSI directive paths be interpreted as relative to the context root, instead of the server root? Default false.
• inputEncoding - The encoding to be assumed for SSI resources if one cannot be determined from the resource itself. Default is the default platform encoding.
• outputEncoding - The encoding to be used for the result of the SSI processing. Default is UTF-8.
• allowExec - Is the exec command enabled? Default is false.

There are several filter init parameters which can be used to configure the behaviour of the SSI filter.

• contentType - A regex pattern that must be matched before SSI processing is applied. When crafting your own pattern, don't forget that a mime content type may be followed by an optional character set in the form "mime/type; charset=set" that you must take into account. Default is "text/x-server-parsed-html(;.*)?".
• debug - Debugging detail level for messages logged by this servlet. Default 0.
• expires - The number of seconds before a page with SSI directives will expire. Default behaviour is for all SSI directives to be evaluated for every request.
• isVirtualWebappRelative - Should "virtual" SSI directive paths be interpreted as relative to the context root, instead of the server root? Default false.
• allowExec - Is the exec command enabled? Default is false.

Server Side Includes are invoked by embedding SSI directives in an HTML document whose type will be processed by the SSI servlet. The directives take the form of an HTML comment. The directive is replaced by the results of interpreting it before sending the page to the client. The general form of a directive is:

<!--#directive [parm=value] -->

The directives are:

• config - <!--#config timefmt="%B %Y" --> Used to set the format of dates and other items processed by SSI
• echo - <!--#echo var="VARIABLE_NAME" --> will be replaced by the value of the variable.
• exec - Used to run commands on the host system.
• include - <!--#include virtual="file-name" --> inserts the contents
• flastmod - <!--#flastmod file="filename.shtml" --> Returns the time that a file was lost modified.
• fsize - <!--#fsize file="filename.shtml" --> Returns the size of a file.
• printenv - <!--#printenv --> Returns the list of all the defined variables.
• set - <!--#set var="foo" value="Bar" --> is used to assign a value to a user-defined variable.
• if elif endif else - Used to create conditional sections. For example:

  <!--#config timefmt="%A" -->
  <!--#if expr="$DATE_LOCAL = /Monday/" -->
  <p>Meeting at 10:00 on Mondays</p>
  <!--#elif expr="$DATE_LOCAL = /Friday/" -->
  <p>Turn in your time card</p>
  <!--#else -->
  <p>Yoga class at noon.</p>
  <!--#endif -->

See the Apache Introduction to SSI for more information on using SSI directives.

The SSI servlet currently implements the following variables: