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`

+ + + + +

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.

+ +

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.)

+ +

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:

+ +

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

+ + +

Modifying static content using a CGI script

+ + +

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

+ +

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

+ +

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.

+ + +

Files with HTTP headers

+ + +

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.

+ +

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

+ + +

Programmer's Note

+ + +

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:

+ +

+ char *handler +

+ +

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.