As we mentioned
in the beginning of this chapter, mod_perl lets you run both scripts
and handlers. The previous example showed a script, which is probably
the most familiar approach to web programming, but the more advanced
use of mod_perl involves writing handlers. Have no fear; writing
handlers is almost as easy as writing scripts and offers a level of
access to Apache's internals that is simply not
possible with conventional CGI scripts.
To create a mod_perl handler module, all that is necessary is to wrap
the code that would have been the body of a script into a
handlersubroutine, add a statement to return the
status to the server when the subroutine has successfully completed,
and add a package declaration at the top of the code.
Just as with scripts, the familiar CGI API may be used. Example 2-4 shows an example.
Example 2-4. ModPerl/Rules1.pm
package ModPerl::Rules1;
use Apache::Constants qw(:common);
sub handler {
print "Content-type: text/plain\n\n";
print "mod_perl rules!\n";
return OK; # We must return a status to mod_perl
}
1; # This is a perl module so we must return true to perl
Alternatively, the mod_perl API can be used. This API provides almost
complete access to the Apache core. In the simple example used here,
either approach is fine, but when lower-level access to Apache is
required, the mod_perl API shown in Example 2-5 must
be used.
Example 2-5. ModPerl/Rules2.pm
package ModPerl::Rules2;
use Apache::Constants qw(:common);
sub handler {
my $r = shift;
$r->send_http_header('text/plain');
$r->print("mod_perl rules!\n");
return OK; # We must return a status to mod_perl
}
1; # This is a perl module so we must return true to perl
Create a directory called ModPerl under one of
the directories in@INC (e.g., under
/usr/lib/perl5/site_perl/5.6.1), and put
Rules1.pm and Rules2.pm
into it. (Note that you will need root access in
order to do this.) The files should include the code from the above
examples. To find out what the @INC directories
are, execute:
Therefore, on our machine, we might place the files in the directory
/usr/lib/perl5/site_perl/5.6.1/ModPerl. By
default, when you work as root, the files are
created with permissions allowing everybody to read them, so here we
don't have to adjust the file permissions (the
server only needs to be able to read those).
Now add the following snippet to
/usr/local/apache/conf/httpd.conf, to configure
mod_perl to execute the ModPerl::Rules1::handler
subroutine whenever a request to mod_perl_rules1
is made:
