Apache::Dispatch - call PerlHandlers with the ease of Registry scripts
Makefile.PL:
# require util since it can be used outside an apache process PREREQ_PM => { 'Apache::Dispatch::Util' => 0.11, }
httpd.conf:
PerlModule Apache::Dispatch PerlModule Bar DispatchExtras Pre Post Error DispatchStat On DispatchISA "My::Utils" DispatchAUTOLOAD Off <Location /Foo> SetHandler perl-script PerlHandler Apache::Dispatch DispatchPrefix Bar DispatchFilter Off </Location>
Apache::Dispatch translates $r->uri into a class and method and runs it as a PerlHandler. Basically, this allows you to call PerlHandlers as you would Regsitry scripts without having to load your httpd.conf with a slurry of <Location> tags.
in httpd.conf PerlModule Apache::Dispatch PerlModule Bar <Location /Foo> SetHandler perl-script PerlHandler Apache::Dispatch DispatchPrefix Bar </Location> in browser: http://localhost/Foo/baz the results are the same as if your httpd.conf looked like: <Location /Foo> SetHandler perl-script PerlHandler Bar->dispatch_baz </Location>
but with the additional security of protecting the class name from the browser and keeping the method name from being called directly. Because any class under the Bar:: hierarchy can be called, one <Location> directive is able to handle all the methods of Bar, Bar::Baz, etc...
DispatchPrefix The base class to be substituted for the $r->location part of the uri. DispatchLocation Using Apache::Dispatch from a <Directory> directive, either directly or from a .htaccess file, will _require_ the use of DispatchLocation, which defines the location from which Apache::Dispatch will start class->method() translation. For example: httpd.conf DocumentRoot /usr/local/apache/htdocs <Directory /usr/local/apache/htdocs/> ... <Directory> .htaccess (in /usr/local/apache/htdocs/Foo) SetHandler perl-script PerlHandler Apache::Dispatch DispatchPrefix Baz DispatchLocation /Foo This allows a request to /Foo/Bar/biff to properly map to Baz::Bar->biff(). While intended specifically for <Directory> configurations, one could use DispatchLocation to further obscure uri translations within <Location> sections as well by changing the part of the uri that is substitued with your module. DispatchExtras An optional list of extra processing to enable per-request. If the main handler is not a valid method call, the request is declined prior to the execution of any of the extra methods. Pre - eval()s Foo->pre_dispatch($r) prior to dispatching the uri. The $@ of the eval is not checked in any way. Post - eval()s Foo->post_dispatch($r) after dispatching the uri. The $@ of the eval is not checked in any way. Error - If the main handler returns other than OK then Foo->error_dispatch($r, $@) is called and return status of it is returned instead. Unlike the pre and post processing routines above, error_dispatch is not wrapped in an eval, so if it dies, the Apache::Dispatch dies, and Apache will process the error using ErrorDocument, custom_response(), etc. With error_dispatch() disabled, the return status of the the main handler is returned to the client. DispatchRequire An optional directive that enables require()ing of the module that is the result of the uri to class->method translation. This allows your configuration to be a bit more dynamic, but also decreases security somewhat. And don't forget that you really should be pre-loading frequently used modules in the parent process to reduce overhead - DispatchRequire is a directive of conveinence. On - require() the module Off - Do not require() the module (Default) DispatchStat An optional directive that enables reloading of the module that is the result of the uri to class->method translation, similar to Apache::Registry, Apache::Reload, or Apache::StatINC. On - Test the called package for modification and reload on change Off - Do not test or reload the package (Default) ISA - Test the called package, and all other packages in the called package's @ISA, and reload on change DispatchAUTOLOAD An optional directive that enables unknown methods to use AutoLoader. It may be applied on a per-server or per-location basis and defaults to Off. Please see the special section on AUTOLOAD below. On - Allow for methods to be defined in AUTOLOAD method Off - Turn off search for AUTOLOAD method (Default) DispatchISA An optional list of parent classes you want your dispatched class to inherit from. DispatchFilter If you have Apache::Filter 1.013 or above installed, you can take advantage of other Apache::Filter aware modules. Please see the section on FILTERING below. In keeping with Apache::Filter standards, PerlSetVar Filter has the same effect as DispatchFilter but with lower precedence. On - make the output of your module Apache::Filter aware Off - do not use Apache::Filter (Default) DispatchDebug Set DispatchDebug to 1 or 2 to control the verbosity of debug statements.
Migrating to Apache::Dispatch is relatively painless - it requires only a few minor code changes. The good news is that once you adapt code to work with Dispatch, it can be used as a conventional mod_perl method handler, requiring only a few considerations. Below are a few things that require attention.
In the interests of security, all handler methods must be prefixed with 'dispatch_', which is added to the uri behind the scenes. Unlike ordinary mod_perl handlers, for Apache::Dispatch there is no default method (with a tiny exception - see NOTES below).
Apache::Dispatch uses object oriented calls behind the scenes. This means that you either need to account for your handler to be called as a method handler, such as
sub dispatch_bar { my $self = shift; # your class my $r = shift; }
or get the Apache request object directly via
sub dispatch_bar { my $r = Apache->request; }
If you want to use the handler unmodified outside of Apache::Dispatch, you must do three things:
prototype your handler: sub dispatch_baz ($$) { my $self = shift; my $r = shift; } change your httpd.conf entry: <Location /Foo> SetHandler perl-script PerlHandler Bar->dispatch_baz </Location> pre-load your module: PerlModule Bar or PerlRequire startup.pl # where startup.pl contains # use Bar;
That's it - now the handler can be swapped in and out of Dispatch without further modification. See the Eagle book on method handlers for more details.
Apache::Dispatch provides for output filtering using Apache::Filter 1.013 and above.
<Location /Foo> SetHandler perl-script PerlHandler Apache::Dispatch Apache::Compress DispatchPrefix Bar DispatchFilter On </Location>
Your handler need do nothing special to make its output the start of the chain - Apache::Dispatch registers itself with Apache::Filter and hides the task from your handler. Thus, any dispatched handler is automatically Apache::Filter ready without the need for additional code.
The only caveat is that you must use the request object that is passed to the handler and not get it directly using Apache->request.
Support for AUTOLOAD has been made optional, but requires special care. Please take the time to read the camel book on using AUTOLOAD with can() and subroutine declarations (3rd ed pp326-329).
Basically, you declare the methods you want AUTOLOAD to capture by name at the top of your script. This is necessary because can() will return true if your class (or any parent class) contains an AUTOLOAD method, but $AUTOLOAD will only be populated for declared method calls. Hence, without a declaration you won't be able to get at the name of the method you want to AUTOLOAD.
DispatchISA introduced some convenience, but some headaches as well - if you inherit from a class that uses AutoLoader then ALL method calls are true. And as just explained, AUTOLOAD() will not know what the called method was. This may represent a problem if you aren't aware that, say, CGI.pm uses AutoLoader and spend a few hours trying to figure out why all of a sudden every URL under Dispatch is bombing. You may want to check out NEXT.pm (available from CPAN) for use in your AUTOLOAD routines to help circumvent this partucular feature.
If you decide to use DispatchISA it is HIGHLY SUGGESTED that you do so with DispatchAUTOLOAD Off (which is the default behavior).
If you define a dispatch_index() method calls to /Foo will default to it. Unfortunately, this implicit translation only happens at the highest level - calls to /Foo/Bar will translate to Foo->Bar() (that is, unless Foo::Bar is your DispatchPrefix, in which case it will work but /Foo/Bar/Baz will not, etc). Explicit calls to /Foo/index follow the normal dispatch rules.
If the uri can be dispatched but contains anything other than [a-zA-Z0-9_/-] Apache::Dispatch declines to handle the request.
Like everything in perl, the package names are case sensitive.
Warnings have been left on, so if you set an invalid class with DispatchISA you will see a message like: Can't locate package Foo::Bar for @Bar::Baz::ISA at .../Apache/Dispatch.pm line 277.
This is alpha software, and as such has not been tested on multiple platforms or environments for security, stability or other concerns. It requires PERL_DIRECTIVE_HANDLERS=1, PERL_LOG_API=1, PERL_HANDLER=1, and maybe other hooks to function properly.
If a module fails reload under DispatchStat, Apache::Dispatch declines the request. This might change to SERVER_ERROR in the future...
perl(1), mod_perl(1), Apache(3), Apache::Filter(3), Apache::Reload(3), Apache::StatINC(3)
Fred Moyer <phred@apache.org>
Geoffrey Young <geoff@cpan.org>
Copyright 2001-2006 Geoffrey Young - all rights reserved.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Apache::Dispatch, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Apache::Dispatch
CPAN shell
perl -MCPAN -e shell install Apache::Dispatch
For more information on module installation, please visit the detailed CPAN module installation guide.