 |
 |
Apache's Handler Use
What is a Handler
|
Related Modules mod_actions mod_asis mod_cgi mod_imap mod_info mod_include mod_mime mod_negotiation mod_status |
Related Directives 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-parsed: Parse for server-side includes. (mod_include)
- 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.