Apache's Handler Use

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This document describes the use of Apache's Handlers.

What is a Handler
Examples
Programmer's Note

What is a Handler

Related Modules	Related Directives
`mod_actions` `mod_asis` `mod_cgi` `mod_imap` `mod_info` `mod_mime` `mod_negotiation` `mod_status`	`Action` `AddHandler` `RemoveHandler` `SetHandler`

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A "handler" is an internal Apache representation of the - action to be performed when a file is called. Generally, files - have implicit handlers, based on the file type. Normally, all - files are simply served by the server, but certain file types - are "handled" separately.

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Apache 1.1 adds the ability to use handlers explicitly. - Based on either filename extensions or on location, handlers - can be specified without relation to file type. This is - advantageous both because it is a more elegant solution, and - because it also allows for both a type and a - handler to be associated with a file. (See also Files with Multiple - Extensions.)

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Handlers can either be built into the server or included in - a module, or they can be added with the Action directive. The - built-in handlers in the standard distribution are as - follows:

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default-handler: Send the file using the - default_handler(), which is the handler used by - default to handle static content. (core)
send-as-is: Send file with HTTP headers - as is. (mod_asis)
cgi-script: Treat the file as a CGI - script. (mod_cgi)
imap-file: Parse as an imagemap rule - file. (mod_imap)
server-info: Get the server's - configuration information. (mod_info)
server-status: Get the server's status - report. (mod_status)
type-map: Parse as a type map file for - content negotiation. (mod_negotiation)

Examples

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Modifying static content using a CGI script

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The following directives will cause requests for files with - the html extension to trigger the launch of the - footer.pl CGI script.

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- Action add-footer /cgi-bin/footer.pl - AddHandler add-footer .html -

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Then the CGI script is responsible for sending the - originally requested document (pointed to by the - PATH_TRANSLATED environment variable) and making - whatever modifications or additions are desired.

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Files with HTTP headers

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The following directives will enable the - send-as-is handler, which is used for files which - contain their own HTTP headers. All files in the - /web/htdocs/asis/ directory will be processed by - the send-as-is handler, regardless of their - filename extensions.

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- <Directory /web/htdocs/asis> - SetHandler send-as-is - </Directory> -

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Programmer's Note

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In order to implement the handler features, an addition has - been made to the Apache API that - you may wish to make use of. Specifically, a new record has - been added to the request_rec structure:

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- char *handler -

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If you wish to have your module engage a handler, you need - only to set r->handler to the name of the - handler at any time prior to the invoke_handler - stage of the request. Handlers are implemented as they were - before, albeit using the handler name instead of a content - type. While it is not necessary, the naming convention for - handlers is to use a dash-separated word, with no slashes, so - as to not invade the media type name-space.