1CGI::Application::DispaUtscehr(3C)ontributed Perl DocumeCnGtIa:t:iAopnplication::Dispatch(3)
2
6 CGI::Application::Dispatch - Dispatch requests to CGI::Application
7 based objects
8
10 Out of Box
11 Under mod_perl:
12 <Location /app>
14 SetHandler perl-script
15 PerlHandler CGI::Application::Dispatch
16 </Location>
17 Under normal cgi:
19 This would be the instance script for your application, such as
21 /cgi-bin/dispatch.cgi:
22 #!/usr/bin/perl
24 use FindBin::Real 'Bin';
25 use lib Bin() . '/../../rel/path/to/my/perllib';
26 use CGI::Application::Dispatch;
27 CGI::Application::Dispatch->dispatch();
28 With a dispatch table
30 package MyApp::Dispatch;
31 use base 'CGI::Application::Dispatch';
32 sub dispatch_args {
34 return {
35 prefix => 'MyApp',
36 table => [
37 '' => { app => 'Welcome', rm => 'start' },
38 ':app/:rm' => { },
39 'admin/:app/:rm' => { prefix => 'MyApp::Admin' },
40 ],
41 };
42 }
43 Under mod_perl:
45 <Location /app>
47 SetHandler perl-script
48 PerlHandler MyApp::Dispatch
49 </Location>
50 Under normal cgi:
52 This would be the instance script for your application, such as
54 /cgi-bin/dispatch.cgi:
55 #!/usr/bin/perl
57 use FindBin::Real 'Bin';
58 use lib Bin() . '/../../rel/path/to/my/perllib';
59 use MyApp::Dispatch;
60 MyApp::Dispatch->dispatch();
61
63 This module provides a way (as a mod_perl handler or running under
64 vanilla CGI) to look at the path (as returned by dispatch_path) of the
65 incoming request, parse off the desired module and its run mode, create
66 an instance of that module and run it.
67 It currently supports both generations of mod_perl (1.x and 2.x).
69 Although, for simplicity, all examples involving Apache configuration
70 and mod_perl code will be shown using mod_perl 1.x. This may change as
71 mp2 usage increases.
72 It will translate a URI like this (under mod_perl):
74 /app/module_name/run_mode
76 or this (vanilla cgi)
78 /app/index.cgi/module_name/run_mode
80 into something that will be functionally similar to this
82 my $app = Module::Name->new(..);
84 $app->mode_param(sub {'run_mode'}); #this will set the run mode
85
87 dispatch(%args)
88 This is the primary method used during dispatch. Even under mod_perl,
89 the handler method uses this under the hood.
90 #!/usr/bin/perl
92 use strict;
93 use CGI::Application::Dispatch;
94 CGI::Application::Dispatch->dispatch(
96 prefix => 'MyApp',
97 default => 'module_name',
98 );
99 This method accepts the following name value pairs:
101 default
103 Specify a value to use for the path if one is not available. This
104 could be the case if the default page is selected (eg: "/" ).
105 prefix
107 This option will set the string that will be prepended to the name
108 of the application module before it is loaded and created. So to
109 use our previous example request of
110 /app/index.cgi/module_name/run_mode
112 This would by default load and create a module named
114 'Module::Name'. But let's say that you have all of your application
115 specific modules under the 'My' namespace. If you set this option
116 to 'My' then it would instead load the 'My::Module::Name'
117 application module instead.
118 args_to_new
120 This is a hash of arguments that are passed into the "new()"
121 constructor of the application.
122 table
124 In most cases, simply using Dispatch with the "default" and
125 "prefix" is enough to simplify your application and your URLs, but
126 there are many cases where you want more power. Enter the dispatch
127 table. Since this table can be slightly complicated, a whole
128 section exists on its use. Please see the "DISPATCH TABLE" section.
129 debug
131 Set to a true value to send debugging output for this module to
132 STDERR. Off by default.
133 error_document
135 This string is similar to Apache ErrorDocument directive. If this
136 value is not present, then Dispatch will return a NOT FOUND error
137 either to the browser with simple hardcoded message (under CGI) or
138 to Apache (under mod_perl).
139 This value can be one of the following:
141 A string with error message - if it starts with a single double-
143 quote character ("""). This double-quote character will be trimmed
144 from final output.
145 A file with content of error document - if it starts with less-than
147 sign ("<"). First character will be excluded as well. Path of this
148 file should be relative to server DOCUMENT_ROOT.
149 A URI to which the application will be redirected - if no leading
151 """ or "<" will be found.
152 Custom messages will be displayed in non mod_perl environment only.
154 (Under mod_perl, please use ErrorDocument directive in Apache
155 configuration files.) This value can contain %s placeholder for
156 sprintf Perl function. This placeholder will be replaced with
157 numeric HTTP error code. Currently CGI::Application::Dispatch uses
158 three HTTP errors:
159 400 Bad Request - If there are invalid characters in module name
161 (parameter :app) or runmode name (parameter :rm).
162 404 Not Found - When the path does not match anything in the
164 "DISPATCH TABLE", or module could not be found in @INC, or run mode
165 did not exist.
166 500 Internal Server Error - If application error occurs.
168 Examples of using error_document (assume error 404 have been
170 returned):
171 # return in browser 'Opss... HTTP Error #404'
173 error_document => '"Opss... HTTP Error #%s'
174 # return contents of file $ENV{DOCUMENT_ROOT}/errors/error404.html
176 error_document => '</errors/error%s.html'
177 # internal redirect to /errors/error404.html
179 error_document => '/errors/error%s.html'
180 # external redirect to
182 # http://host.domain/cgi-bin/errors.cgi?error=404
183 error_document => 'http://host.domain/cgi-bin/errors.cgi?error=%s'
184 auto_rest
186 This tells Dispatch that you are using REST by default and that you
187 care about which HTTP method is being used. Dispatch will append
188 the HTTP method name (upper case by default) to the run mode that
189 is determined after finding the appropriate dispatch rule. So a GET
190 request that translates into "MyApp::Module->foo" will become
191 "MyApp::Module->foo_GET".
192 This can be overridden on a per-rule basis in a custom dispatch
194 table.
195 auto_rest_lc
197 In combinaion with auto_rest this tells Dispatch that you prefer
198 lower cased HTTP method names. So instead of "foo_POST" and
199 "foo_GET" you'll have "foo_post" and "foo_get".
200 dispatch_path()
202 This method returns the path that is to be processed.
203 By default it returns the value of $ENV{PATH_INFO} (or "$r->path_info"
205 under mod_perl) which should work for most cases. It allows the
206 ability for subclasses to override the value if they need to do
207 something more specific.
208 handler()
210 This method is used so that this module can be run as a mod_perl
211 handler. When it creates the application module it passes the $r
212 argument into the PARAMS hash of new()
213 <Location /app>
215 SetHandler perl-script
216 PerlHandler CGI::Application::Dispatch
217 PerlSetVar CGIAPP_DISPATCH_PREFIX MyApp
218 PerlSetVar CGIAPP_DISPATCH_DEFAULT /module_name
219 </Location>
220 The above example would tell apache that any url beginning with /app
222 will be handled by CGI::Application::Dispatch. It also sets the prefix
223 used to create the application module to 'MyApp' and it tells
224 CGI::Application::Dispatch that it shouldn't set the run mode but that
225 it will be determined by the application module as usual (through the
226 query string). It also sets a default application module to be used if
227 there is no path. So, a url of "/app/module_name" would create an
228 instance of "MyApp::Module::Name".
229 Using this method will add the "Apache-"request> object to your
231 application's "PARAMS" as 'r'.
232 # inside your app
234 my $request = $self->param('r');
235 If you need more customization than can be accomplished with just
237 prefix and default, then it would be best to just subclass
238 CGI::Application::Dispatch and override dispatch_args since "handler()"
239 uses dispatch to do the heavy lifting.
240 package MyApp::Dispatch;
242 use base 'CGI::Application::Dispatch';
243 sub dispatch_args {
245 return {
246 prefix => 'MyApp',
247 table => [
248 '' => { app => 'Welcome', rm => 'start' },
249 ':app/:rm' => { },
250 'admin/:app/:rm' => { prefix => 'MyApp::Admin' },
251 ],
252 args_to_new => {
253 PARAMS => {
254 foo => 'bar',
255 baz => 'bam',
256 },
257 }
258 };
259 }
260 1;
262 And then in your httpd.conf
264 <Location /app>
266 SetHandler perl-script
267 PerlHandler MyApp::Dispatch
268 </Location>
269 dispatch_args()
271 Returns a hashref of args that will be passed to dispatch(). It will
272 return the following structure by default.
273 {
275 prefix => '',
276 args_to_new => {},
277 table => [
278 ':app' => {},
279 ':app/:rm' => {},
280 ],
281 }
282 This is the perfect place to override when creating a subclass to
284 provide a richer dispatch table.
285 When called, it receives 1 argument, which is a reference to the hash
287 of args passed into dispatch.
288 translate_module_name($input)
290 This method is used to control how the module name is translated from
291 the matching section of the path (see "Path Parsing"). The main reason
292 that this method exists is so that it can be overridden if it doesn't
293 do exactly what you want.
294 The following transformations are performed on the input:
296 The text is split on '_'s (underscores) and each word has its first
298 letter capitalized. The words are then joined back together and each
299 instance of an underscore is replaced by '::'.
300 The text is split on '-'s (hyphens) and each word has its first letter
301 capitalized. The words are then joined back together and each instance
302 of a hyphen removed.
303 Here are some examples to make it even clearer:
305 module_name => Module::Name
307 module-name => ModuleName
308 admin_top-scores => Admin::TopScores
309 require_module($module_name)
311 This class method is used internally by CGI::Application::Dispatch to
312 take a module name (supplied by get_module_name) and require it in a
313 secure fashion. It is provided as a public class method so that if you
314 override other functionality of this module, you can still safely
315 require user specified modules. If there are any problems requiring the
316 named module, then we will "croak".
317 CGI::Application::Dispatch->require_module('MyApp::Module::Name');
319
321 Sometimes it's easiest to explain with an example, so here you go:
322 CGI::Application::Dispatch->dispatch(
324 prefix => 'MyApp',
325 args_to_new => {
326 TMPL_PATH => 'myapp/templates'
327 },
328 table => [
329 '' => { app => 'Blog', rm => 'recent'},
330 'posts/:category' => { app => 'Blog', rm => 'posts' },
331 ':app/:rm/:id' => { app => 'Blog' },
332 'date/:year/:month?/:day?' => {
333 app => 'Blog',
334 rm => 'by_date',
335 args_to_new => { TMPL_PATH => "events/" },
336 },
337 ]
338 );
339 So first, this call to dispatch sets the prefix and passes a
341 "TMPL_PATH" into args_to_new. Next it sets the table.
342 VOCABULARY
344 Just so we all understand what we're talking about....
345 A table is an array where the elements are gouped as pairs (similar to
347 a hash's key-value pairs, but as an array to preserve order). The first
348 element of each pair is called a "rule". The second element in the pair
349 is called the rule's "arg list". Inside a rule there are slashes "/".
350 Anything set of characters between slashes is called a "token".
351 URL MATCHING
353 When a URL comes in, Dispatch tries to match it against each rule in
354 the table in the order in which the rules are given. The first one to
355 match wins.
356 A rule consists of slashes and tokens. A token can one of the following
358 types:
359 literal
361 Any token which does not start with a colon (":") is taken to be a
362 literal string and must appear exactly as-is in the URL in order to
363 match. In the rule
364 'posts/:category'
366 "posts" is a literal token.
368 variable
370 Any token which begins with a colon (":") is a variable token.
371 These are simply wild-card place holders in the rule that will
372 match anything in the URL that isn't a slash. These variables can
373 later be referred to by using the "$self->param" mechanism. In the
374 rule
375 'posts/:category'
377 ":category" is a variable token. If the URL matched this rule, then
379 you could retrieve the value of that token from whithin your
380 application like so:
381 my $category = $self->param('category');
383 There are some variable tokens which are special. These can be used
385 to further customize the dispatching.
386 :app
388 This is the module name of the application. The value of this
389 token will be sent to the translate_module_name method and then
390 prefixed with the prefix if there is one.
391 :rm This is the run mode of the application. The value of this
393 token will be the actual name of the run mode used. The run
394 mode can be optional, as noted below. Example:
395 /foo/:rm?
397 If no run mode is found, it will default to using the
399 "start_mode()", just like invoking CGI::Application directly.
400 Both of these URLs would end up dispatching to the start mode
401 associated with /foo:
402 /foo/
404 /foo
405 optional-variable
407 Any token which begins with a colon (":") and ends with a question
408 mark (<?>) is considered optional. If the rest of the URL matches
409 the rest of the rule, then it doesn't matter whether it contains
410 this token or not. It's best to only include optional-variable
411 tokens at the end of your rule. In the rule
412 'date/:year/:month?/:day?'
414 ":month?" and ":day?" are optional-variable tokens.
416 Just like with variable tokens, optional-variable tokens' values
418 can also be retrieved by the application, if they existed in the
419 URL.
420 if( defined $self->param('month') ) {
422 ...
423 }
424 wildcard
426 The wildcard token "*" allows for partial matches. The token MUST
427 appear at the end of the rule.
428 'posts/list/*'
430 By default, the "dispatch_url_remainder" param is set to the
432 remainder of the URL matched by the *. The name of the param can be
433 changed by setting "*" argument in the "ARG LIST".
434 'posts/list/*' => { '*' => 'post_list_filter' }
436 method
438 You can also dispatch based on HTTP method. This is similar to
439 using auto_rest but offers more fine grained control. You include
440 the method (case insensitive) at the end of the rule and enclose it
441 in square brackets.
442 ':app/news[post]' => { rm => 'add_news' },
444 ':app/news[get]' => { rm => 'news' },
445 ':app/news[delete]' => { rm => 'delete_news' },
446 The main reason that we don't use regular expressions for dispatch
448 rules is that regular expressions provide no mechanism for named back
449 references, like variable tokens do.
450 ARG LIST
452 Each rule can have an accompanying arg-list. This arg list can contain
453 special arguments that override something set higher up in dispatch for
454 this particular URL, or just have additional args passed available in
455 "$self->param()"
456 For instance, if you want to override prefix for a specific rule, then
458 you can do so.
459 'admin/:app/:rm' => { prefix => 'MyApp::Admin' },
461
463 This section will describe how the application module and run mode are
464 determined from the path if no "DISPATCH TABLE" is present, and what
465 options you have to customize the process. The value for the path to
466 be parsed is retrieved from the dispatch_path method, which by default
467 uses the "PATH_INFO" environment variable.
468 Getting the module name
470 To get the name of the application module the path is split on
471 backslahes ("/"). The second element of the returned list (the first
472 is empty) is used to create the application module. So if we have a
473 path of
474 /module_name/mode1
476 then the string 'module_name' is used. This is passed through the
478 translate_module_name method. Then if there is a "prefix" (and there
479 should always be a prefix) it is added to the beginning of this new
480 module name with a double colon "::" separating the two.
481 If you don't like the exact way that this is done, don't fret you do
483 have a couple of options. First, you can specify a "DISPATCH TABLE"
484 which is much more powerful and flexible (in fact this default behavior
485 is actually implemented internally with a dispatch table). Or if you
486 want something a little simpler, you can simply subclass and extend the
487 translate_module_name method.
488 Getting the run mode
490 Just like the module name is retrieved from splitting the path on
491 slashes, so is the run mode. Only instead of using the second element
492 of the resulting list, we use the third as the run mode. So, using the
493 same example, if we have a path of
494 /module_name/mode2
496 Then the string 'mode2' is used as the run mode.
498
500 • CGI query strings
501 CGI query strings are unaffected by the use of "PATH_INFO" to
503 obtain the module name and run mode. This means that any other
504 modules you use to get access to you query argument (ie, CGI,
505 Apache::Request) should not be affected. But, since the run
506 mode may be determined by CGI::Application::Dispatch having a
507 query argument named 'rm' will be ignored by your application
508 module.
509
511 With a dispatch script, you can fairly clean URLS like this:
512 /cgi-bin/dispatch.cgi/module_name/run_mode
514 However, including "/cgi-bin/dispatch.cgi" in ever URL doesn't add any
516 value to the URL, so it's nice to remove it. This is easily done if you
517 are using the Apache web server with "mod_rewrite" available. Adding
518 the following to a ".htaccess" file would allow you to simply use:
519 /module_name/run_mode
521 If you have problems with mod_rewrite, turn on debugging to see exactly
523 what's happening:
524 RewriteLog /home/project/logs/alpha-rewrite.log
526 RewriteLogLevel 9
527 mod_rewrite related code in the dispatch script.
529 This seemed necessary to put in the dispatch script to make mod_rewrite
530 happy. Perhaps it's specific to using "RewriteBase".
531 # mod_rewrite alters the PATH_INFO by turning it into a file system path,
533 # so we repair it.
534 $ENV{PATH_INFO} =~ s/^$ENV{DOCUMENT_ROOT}// if defined $ENV{PATH_INFO};
535 Simple Apache Example
537 RewriteEngine On
538 # You may want to change the base if you are using the dispatcher within a
540 # specific directory.
541 RewriteBase /
542 # If an actual file or directory is requested, serve directly
544 RewriteCond %{REQUEST_FILENAME} !-f
545 RewriteCond %{REQUEST_FILENAME} !-d
546 # Otherwise, pass everything through to the dispatcher
548 RewriteRule ^(.*)$ /cgi-bin/dispatch.cgi/$1 [L,QSA]
549 More complex rewrite: dispatching "/" and multiple developers
551 Here is a more complex example that dispatches "/", which would
552 otherwise be treated as a directory, and also supports multiple
553 developer directories, so "/~mark" has its own separate dispatching
554 system beneath it.
555 Note that order matters here! The Location block for "/" needs to come
557 before the user blocks.
558 <Location />
560 RewriteEngine On
561 RewriteBase /
562 # Run "/" through the dispatcher
564 RewriteRule ^home/project/www/$ /cgi-bin/dispatch.cgi [L,QSA]
565 # Don't apply this rule to the users sub directories.
567 RewriteCond %{REQUEST_URI} !^/~.*$
568 # If an actual file or directory is requested, serve directly
569 RewriteCond %{REQUEST_FILENAME} !-f
570 RewriteCond %{REQUEST_FILENAME} !-d
571 # Otherwise, pass everything through to the dispatcher
572 RewriteRule ^(.*)$ /cgi-bin/dispatch.cgi/$1 [L,QSA]
573 </Location>
574 <Location /~mark>
576 RewriteEngine On
577 RewriteBase /~mark
578 # Run "/" through the dispatcher
580 RewriteRule ^/home/mark/www/$ /~mark/cgi-bin/dispatch.cgi [L,QSA]
581 # Otherwise, if an actual file or directory is requested,
583 # serve directly
584 RewriteCond %{REQUEST_FILENAME} !-f
585 RewriteCond %{REQUEST_FILENAME} !-d
586 # Otherwise, pass everything through to the dispatcher
588 RewriteRule ^(.*)$ /~mark/cgi-bin/dispatch.cgi/$1 [L,QSA]
589 # These examples may also be helpful, but are unrelated to dispatching.
591 SetEnv DEVMODE mark
592 SetEnv PERL5LIB /home/mark/perllib:/home/mark/config
593 ErrorDocument 404 /~mark/errdocs/404.html
594 ErrorDocument 500 /~mark/errdocs/500.html
595 </Location>
596
598 While Dispatch tries to be flexible, it won't be able to do everything
599 that people want. Hopefully we've made it flexible enough so that if it
600 doesn't do The Right Thing you can easily subclass it.
601
603 Michael Peters <mpeters@plusthree.com>
604 Thanks to Plus Three, LP (http://www.plusthree.com) for sponsoring my
606 work on this module
607
609 This module is a part of the larger CGI::Application community. If you
610 have questions or comments about this module then please join us on the
611 cgiapp mailing list by sending a blank message to
612 "cgiapp-subscribe@lists.erlbaum.net". There is also a community wiki
613 located at <http://www.cgi-app.org/>
614
616 A public source code repository for this project is hosted here:
617 http://code.google.com/p/cgi-app-modules/source/checkout
619
621 • Shawn Sorichetti
622 • Timothy Appnel
624 • dsteinbrunner
626 • ZACKSE
628 • Stew Heckenberg
630 • Drew Taylor <drew@drewtaylor.com>
632 • James Freeman <james.freeman@smartsurf.org>
634 • Michael Graham <magog@the-wire.com>
636 • Cees Hek <ceeshek@gmail.com>
638 • Mark Stosberg <mark@summersault.com>
640 • Viacheslav Sheveliov <slavash@aha.ru>
642
644 Since C::A::Dispatch will dynamically choose which modules to use as
645 the content generators, it may give someone the ability to execute
646 random modules on your system if those modules can be found in you
647 path. Of course those modules would have to behave like
648 CGI::Application based modules, but that still opens up the door more
649 than most want. This should only be a problem if you don't use a
650 prefix. By using this option you are only allowing Dispatch to pick
651 from a namespace of modules to run.
652
654 CGI::Application, Apache::Dispatch
655
657 Copyright Michael Peters and Mark Stosberg 2008, all rights reserved.
658 This library is free software; you can redistribute it and/or modify it
660 under the same terms as Perl itself.
661perl v5.34.0 2022-01-20 CGI::Application::Dispatch(3)