3 Catalyst::Manual::Tutorial::Authentication - Catalyst Tutorial - Part 5: Authentication
8 This is B<Part 5 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
36 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::Appendices>
59 Now that we finally have a simple yet functional application, we can
60 focus on providing authentication (with authorization coming next in
63 This part of the tutorial is divided into two main sections: 1) basic,
64 cleartext authentication and 2) hash-based authentication.
66 You can checkout the source code for this example from the catalyst
67 subversion repository as per the instructions in
68 L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
71 =head1 BASIC AUTHENTICATION
73 This section explores how to add authentication logic to a Catalyst
77 =head2 Add Users and Roles to the Database
79 First, we add both user and role information to the database (we will
80 add the role information here although it will not be used until the
81 authorization section, Part 6). Create a new SQL script file by opening
82 C<myapp02.sql> in your editor and insert:
85 -- Add users and roles tables, along with a many-to-many join table
88 id INTEGER PRIMARY KEY,
97 id INTEGER PRIMARY KEY,
100 CREATE TABLE user_roles (
103 PRIMARY KEY (user_id, role_id)
106 -- Load up some initial test data
108 INSERT INTO users VALUES (1, 'test01', 'mypass', 't01@na.com', 'Joe', 'Blow', 1);
109 INSERT INTO users VALUES (2, 'test02', 'mypass', 't02@na.com', 'Jane', 'Doe', 1);
110 INSERT INTO users VALUES (3, 'test03', 'mypass', 't03@na.com', 'No', 'Go', 0);
111 INSERT INTO roles VALUES (1, 'user');
112 INSERT INTO roles VALUES (2, 'admin');
113 INSERT INTO user_roles VALUES (1, 1);
114 INSERT INTO user_roles VALUES (1, 2);
115 INSERT INTO user_roles VALUES (2, 1);
116 INSERT INTO user_roles VALUES (3, 1);
118 Then load this into the C<myapp.db> database with the following command:
120 $ sqlite3 myapp.db < myapp02.sql
123 =head2 Add User and Role Information to DBIC Schema
125 Although we could manually edit the DBIC schema information to include
126 the new tables added in the previous step, let's use the C<create=static>
127 option on the DBIC model helper to do most of the work for us:
129 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
130 create=static components=TimeStamp dbi:SQLite:myapp.db
131 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
132 exists "/root/dev/MyApp/script/../t"
133 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
134 Schema dump completed.
135 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
137 $ ls lib/MyApp/Schema/Result
138 Authors.pm BookAuthors.pm Books.pm Roles.pm UserRoles.pm Users.pm
140 Notice how the helper has added three new table-specific result source
141 files to the C<lib/MyApp/Schema/Result> directory. And, more
142 importantly, even if there were changes to the existing result source
143 files, those changes would have only been written above the C<# DO NOT
144 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-edited
145 enhancements would have been preserved.
147 Speaking of "hand-edit ted enhancements," we should now add
148 relationship information to the three new result source files. Edit
149 each of these files and add the following information between the C<#
150 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
152 C<lib/MyApp/Schema/Result/Users.pm>:
160 # 1) Name of relationship, DBIC will create accessor with this name
161 # 2) Name of the model class referenced by this relationship
162 # 3) Column name in *foreign* table (aka, foreign key in peer table)
163 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::Result::UserRoles', 'user_id');
167 # 1) Name of relationship, DBIC will create accessor with this name
168 # 2) Name of has_many() relationship this many_to_many() is shortcut for
169 # 3) Name of belongs_to() relationship in model class of has_many() above
170 # You must already have the has_many() defined to use a many_to_many().
171 __PACKAGE__->many_to_many(roles => 'map_user_role', 'role');
174 C<lib/MyApp/Schema/Result/Roles.pm>:
182 # 1) Name of relationship, DBIC will create accessor with this name
183 # 2) Name of the model class referenced by this relationship
184 # 3) Column name in *foreign* table (aka, foreign key in peer table)
185 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::Result::UserRoles', 'role_id');
188 C<lib/MyApp/Schema/Result/UserRoles.pm>:
196 # 1) Name of relationship, DBIC will create accessor with this name
197 # 2) Name of the model class referenced by this relationship
198 # 3) Column name in *this* table
199 __PACKAGE__->belongs_to(user => 'MyApp::Schema::Result::Users', 'user_id');
203 # 1) Name of relationship, DBIC will create accessor with this name
204 # 2) Name of the model class referenced by this relationship
205 # 3) Column name in *this* table
206 __PACKAGE__->belongs_to(role => 'MyApp::Schema::Result::Roles', 'role_id');
209 The code for these three sets of updates is obviously very similar to
210 the edits we made to the C<Books>, C<Authors>, and C<BookAuthors>
211 classes created in Part 3.
213 Note that we do not need to make any change to the
214 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to load all
215 of the Result Class and ResultSet Class files it finds in below the
216 C<lib/MyApp/Schema> directory, so it will automatically pick up our
217 new table information.
220 =head2 Sanity-Check Reload of Development Server
222 We aren't ready to try out the authentication just yet; we only want
223 to do a quick check to be sure our model loads correctly. Press
224 C<Ctrl-C> to kill the previous server instance (if it's still running)
227 $ script/myapp_server.pl
229 Look for the three new model objects in the startup debug output:
232 .-------------------------------------------------------------------+----------.
234 +-------------------------------------------------------------------+----------+
235 | MyApp::Controller::Books | instance |
236 | MyApp::Controller::Root | instance |
237 | MyApp::Model::DB | instance |
238 | MyApp::Model::DB::Author | class |
239 | MyApp::Model::DB::Books | class |
240 | MyApp::Model::DB::BookAuthors | class |
241 | MyApp::Model::DB::Roles | class |
242 | MyApp::Model::DB::Users | class |
243 | MyApp::Model::DB::UserRoles | class |
244 | MyApp::View::TT | instance |
245 '-------------------------------------------------------------------+----------'
248 Again, notice that your "Result Class" classes have been "re-loaded"
249 by Catalyst under C<MyApp::Model>.
252 =head2 Include Authentication and Session Plugins
254 Edit C<lib/MyApp.pm> and update it as follows (everything below
255 C<StackTrace> is new):
258 use Catalyst qw/-Debug
267 Session::Store::FastMmap
268 Session::State::Cookie
271 B<Note:> As discussed in MoreCatalystBasics, different versions of
272 C<Catalyst::Devel> have used a variety of methods to load the plugins.
273 You can put the plugins in the C<use Catalyst> statement if you prefer.
275 The C<Authentication> plugin supports Authentication while the
276 C<Session> plugins are required to maintain state across multiple HTTP
279 Note that the only required Authentication class is the main one. This
280 is a change that occurred in version 0.09999_01 of the
281 C<Authentication> plugin. You B<do not need> to specify a particular
282 Authentication::Store or Authentication::Credential plugin. Instead,
283 indicate the Store and Credential you want to use in your application
284 configuration (see below).
286 Note that there are several options for
287 L<Session::Store|Catalyst::Plugin::Session::Store>
288 (L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap>
289 is generally a good choice if you are on Unix; try
290 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
291 are on Win32) -- consult
292 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
293 for additional information and options (for example to use a database-
294 backed session store).
297 =head2 Configure Authentication
299 Although C<__PACKAGE__-E<gt>config(name =E<gt> 'value');> is still
300 supported, newer Catalyst applications tend to place all configuration
301 information in C<myapp.conf> and automatically load this information
302 into C<MyApp-E<gt>config> using the
303 L<ConfigLoader|Catalyst::Plugin::ConfigLoader> plugin.
305 As discussed in Part 3 of the tutorial, Catalyst has recently
306 switched from a default config file format of YAML to
307 L<Config::General|Config::General> (an apache-like format). In case
308 you are using a version of Catalyst earlier than v5.7014, delete the
309 C<myapp.yml>, or convert it to .conf format using the TIP in
310 L<Catalyst::Manual::MoreCatalystBasics/EDIT THE LIST OF CATALYST PLUGINS>
311 then simply follow the directions below to create a new C<myapp.conf>
312 file. Although we will use the C<Config::General> format here because
313 YAML files can be difficult to cut and paste in certain environments,
314 you are free to use any format supported by
315 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
316 L<Config::Any|Config::Any> -- Catalyst will transparently handle the
319 Here, we need to load several parameters that tell
320 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
321 where to locate information in your database. To do this, edit the
322 C<myapp.conf> file and update it to match:
324 # rename this file to MyApp.yml and put a : in front of "name" if
325 # you want to use yaml like in old versions of Catalyst
332 # Note: this first definition would be the same as setting
333 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
334 # ->{credential} = 'Password' in lib/MyApp.pm
336 # Specify that we are going to do password-based auth
338 # This is the name of the field in the users table with the
339 # password stored in it
340 password_field password
341 # We are using an unencrypted password for now
345 # Use DBIC to retrieve username, password & role information
347 # This is the model object created by Catalyst::Model::DBIC
348 # from your schema (you created 'MyApp::Schema::Result::User'
349 # but as the Catalyst startup debug messages show, it was
350 # loaded as 'MyApp::Model::DB::Users').
351 # NOTE: Omit 'MyApp::Model' here just as you would when using
352 # '$c->model("DB::Users)'
359 Inline comments in the code above explain how each field is being used.
362 =head2 Add Login and Logout Controllers
364 Use the Catalyst create script to create two stub controller files:
366 $ script/myapp_create.pl controller Login
367 $ script/myapp_create.pl controller Logout
369 You could easily use a single controller here. For example, you could
370 have a C<User> controller with both C<login> and C<logout> actions.
371 Remember, Catalyst is designed to be very flexible, and leaves such
372 matters up to you, the designer and programmer.
374 Then open C<lib/MyApp/Controller/Login.pm>, locate the
375 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
376 are using an older version of Catalyst) that was automatically
377 inserted by the helpers when we created the Login controller above,
378 and update the definition of C<sub index> to match:
386 sub index :Path :Args(0) {
389 # Get the username and password from form
390 my $username = $c->request->params->{username} || "";
391 my $password = $c->request->params->{password} || "";
393 # If the username and password values were found in form
394 if ($username && $password) {
395 # Attempt to log the user in
396 if ($c->authenticate({ username => $username,
397 password => $password } )) {
398 # If successful, then let them use the application
399 $c->response->redirect($c->uri_for(
400 $c->controller('Books')->action_for('list')));
403 # Set an error message
404 $c->stash->{error_msg} = "Bad username or password.";
408 # If either of above don't work out, send to the login page
409 $c->stash->{template} = 'login.tt2';
412 This controller fetches the C<username> and C<password> values from the
413 login form and attempts to authenticate the user. If successful, it
414 redirects the user to the book list page. If the login fails, the user
415 will stay at the login page and receive an error message. If the
416 C<username> and C<password> values are not present in the form, the
417 user will be taken to the empty login form.
419 Note that we could have used something like "C<sub default :Path>",
420 however, it is generally recommended (partly for historical reasons,
421 and partly for code clarity) only to use C<default> in
422 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
423 found page for the application.
425 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
426 specifically match the URL C</login>. C<Path> actions (aka, "literal
427 actions") create URI matches relative to the namespace of the
428 controller where they are defined. Although C<Path> supports
429 arguments that allow relative and absolute paths to be defined, here
430 we use an empty C<Path> definition to match on just the name of the
431 controller itself. The method name, C<index>, is arbitrary. We make
432 the match even more specific with the C<:Args(0)> action modifier --
433 this forces the match on I<only> C</login>, not
434 C</login/somethingelse>.
436 Next, update the corresponding method in
437 C<lib/MyApp/Controller/Logout.pm> to match:
445 sub index :Path :Args(0) {
448 # Clear the user's state
451 # Send the user to the starting point
452 $c->response->redirect($c->uri_for('/'));
455 As with the login controller, be sure to delete the
456 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
457 line of the C<sub index>.
460 =head2 Add a Login Form TT Template Page
462 Create a login form by opening C<root/src/login.tt2> and inserting:
464 [% META title = 'Login' %]
467 <form method="post" action="[% c.uri_for('/login') %]">
471 <td><input type="text" name="username" size="40" /></td>
475 <td><input type="password" name="password" size="40" /></td>
478 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
484 =head2 Add Valid User Check
486 We need something that provides enforcement for the authentication
487 mechanism -- a I<global> mechanism that prevents users who have not
488 passed authentication from reaching any pages except the login page.
489 This is generally done via an C<auto> action/method (prior to Catalyst
490 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
491 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
493 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
494 the following method:
498 Check if there is a user and, if not, forward to login page
502 # Note that 'auto' runs after 'begin' but before your actions and that
503 # 'auto's "chain" (all from application path to most specific class are run)
504 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
508 # Allow unauthenticated users to reach the login page. This
509 # allows unauthenticated users to reach any action in the Login
510 # controller. To lock it down to a single action, we could use:
511 # if ($c->action eq $c->controller('Login')->action_for('index'))
512 # to only allow unauthenticated access to the 'index' action we
514 if ($c->controller eq $c->controller('Login')) {
518 # If a user doesn't exist, force login
519 if (!$c->user_exists) {
520 # Dump a log message to the development server debug output
521 $c->log->debug('***Root::auto User not found, forwarding to /login');
522 # Redirect the user to the login page
523 $c->response->redirect($c->uri_for('/login'));
524 # Return 0 to cancel 'post-auto' processing and prevent use of application
528 # User found, so return 1 to continue with processing after this 'auto'
533 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
534 every C<auto> method from the application/root controller down to the
535 most specific controller will be called. By placing the
536 authentication enforcement code inside the C<auto> method of
537 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
538 called for I<every> request that is received by the entire
542 =head2 Displaying Content Only to Authenticated Users
544 Let's say you want to provide some information on the login page that
545 changes depending on whether the user has authenticated yet. To do
546 this, open C<root/src/login.tt2> in your editor and add the following
547 lines to the bottom of the file:
552 # This code illustrates how certain parts of the TT
553 # template will only be shown to users who have logged in
555 [% IF c.user_exists %]
556 Please Note: You are already logged in as '[% c.user.username %]'.
557 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
559 You need to log in to use this application.
562 Note that this whole block is a comment because the "#" appears
563 immediate after the "[%" (with no spaces in between). Although it
564 can be a handy way to temporarily "comment out" a whole block of
565 TT code, it's probably a little too subtle for use in "normal"
570 Although most of the code is comments, the middle few lines provide a
571 "you are already logged in" reminder if the user returns to the login
572 page after they have already authenticated. For users who have not yet
573 authenticated, a "You need to log in..." message is displayed (note the
574 use of an IF-THEN-ELSE construct in TT).
577 =head2 Try Out Authentication
579 Press C<Ctrl-C> to kill the previous server instance (if it's still
580 running) and restart it:
582 $ script/myapp_server.pl
584 B<IMPORTANT NOTE:> If you are having issues with authentication on
585 Internet Explorer, be sure to check the system clocks on both your
586 server and client machines. Internet Explorer is very picky about
587 timestamps for cookies. You can quickly sync a Debian system by
588 installing the "ntpdate" package:
590 sudo aptitude -y install ntpdate
592 And then run the following command:
596 Or, depending on your firewall configuration:
598 sudo ntpdate-debian -u
600 Note: NTP can be a little more finicky about firewalls because it uses
601 UDP vs. the more common TCP that you see with most Internet protocols.
602 Worse case, you might have to manually set the time on your development
603 box instead of using NTP.
605 Now trying going to L<http://localhost:3000/books/list> and you should
606 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
607 if necessary (the "You are already logged in" message should I<not>
608 appear -- if it does, click the C<logout> button and try again). Note
609 the C<***Root::auto User not found...> debug message in the
610 development server output. Enter username C<test01> and password
611 C<mypass>, and you should be taken to the Book List page.
613 Open C<root/src/books/list.tt2> and add the following lines to the
614 bottom (below the closing </table> tag):
617 <a href="[% c.uri_for('/login') %]">Login</a>
618 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
621 Reload your browser and you should now see a "Login" and "Create" links
622 at the bottom of the page (as mentioned earlier, you can update template
623 files without reloading the development server). Click the first link
624 to return to the login page. This time you I<should> see the "You are
625 already logged in" message.
627 Finally, click the C<You can logout here> link on the C</login> page.
628 You should stay at the login page, but the message should change to "You
629 need to log in to use this application."
632 =head1 USING PASSWORD HASHES
634 In this section we increase the security of our system by converting
635 from cleartext passwords to SHA-1 password hashes.
637 B<Note:> This section is optional. You can skip it and the rest of the
638 tutorial will function normally.
640 Be aware that even with the techniques shown in this section, the browser
641 still transmits the passwords in cleartext to your application. We are
642 just avoiding the I<storage> of cleartext passwords in the database by
643 using a SHA-1 hash. If you are concerned about cleartext passwords
644 between the browser and your application, consider using SSL/TLS, made
645 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL. You should
646 also consider adding a "salt" mechanism to your hashed passwords to
647 mitigate the risk of a "rainbow table" crack against your passwords (see
648 L<Catalyst::Authentication::Credential::Password|Catalyst::Authentication::Credential::Password>
649 for more information on using a salt value).
652 =head2 Get a SHA-1 Hash for the Password
654 Catalyst uses the C<Digest> module to support a variety of hashing
655 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
656 First, we should compute the SHA-1 hash for the "mypass" password we are
657 using. The following command-line Perl script provides a "quick and
658 dirty" way to do this:
660 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
661 e727d1464ae12436e899a726da5b2f11d8381b26
663 B<Note:> You should probably modify this code for production use to
664 not read the password from the command line. By having the script
665 prompt for the cleartext password, it avoids having the password linger
666 in forms such as your C<.bash_history> files (assuming you are using
667 BASH as your shell). An example of such a script can be found in
671 =head2 Switch to SHA-1 Password Hashes in the Database
673 Next, we need to change the C<password> column of our C<users> table to
674 store this hash value vs. the existing cleartext password. Open
675 C<myapp03.sql> in your editor and enter:
678 -- Convert passwords to SHA-1 hashes
680 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
681 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
682 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
684 Then use the following command to update the SQLite database:
686 $ sqlite3 myapp.db < myapp03.sql
688 B<Note:> We are using SHA-1 hashes here, but many other hashing
689 algorithms are supported. See C<Digest> for more information.
692 =head2 Enable SHA-1 Hash Passwords in
693 C<Catalyst::Plugin::Authentication::Store::DBIC>
695 Edit C<myapp.conf> and update it to match (the C<password_type> and
696 C<password_hash_type> are new, everything else is the same):
698 # rename this file to MyApp.yml and put a : in front of "name" if
699 # you want to use yaml like in old versions of Catalyst
706 # Note this first definition would be the same as setting
707 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
708 # ->{credential} = 'Password' in lib/MyApp.pm
710 # Specify that we are going to do password-based auth
712 # This is the name of the field in the users table with the
713 # password stored in it
714 password_field password
715 # Switch to more secure hashed passwords
717 # Use the SHA-1 hashing algorithm
718 password_hash_type SHA-1
721 # Use DBIC to retrieve username, password & role information
723 # This is the model object created by Catalyst::Model::DBIC
724 # from your schema (you created 'MyApp::Schema::Result::User'
725 # but as the Catalyst startup debug messages show, it was
726 # loaded as 'MyApp::Model::DB::Users').
727 # NOTE: Omit 'MyApp::Model' here just as you would when using
728 # '$c->model("DB::Users)'
736 =head2 Try Out the Hashed Passwords
738 Press C<Ctrl-C> to kill the previous server instance (if it's still
739 running) and restart it:
741 $ script/myapp_server.pl
743 You should now be able to go to L<http://localhost:3000/books/list> and
744 login as before. When done, click the "logout" link on the login page
745 (or point your browser at L<http://localhost:3000/logout>).
748 =head1 USING THE SESSION FOR FLASH
750 As discussed in Part 3 of the tutorial, C<flash> allows you to set
751 variables in a way that is very similar to C<stash>, but it will
752 remain set across multiple requests. Once the value is read, it
753 is cleared (unless reset). Although C<flash> has nothing to do with
754 authentication, it does leverage the same session plugins. Now that
755 those plugins are enabled, let's go back and update the "delete
756 and redirect with query parameters" code seen at the end of the
757 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
758 tutorial to take advantage of C<flash>.
760 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
761 to match the following (everything after the model search line of code
770 sub delete :Chained('object') :PathPart('delete') :Args(0) {
773 # Use the book object saved by 'object' and delete it along
774 # with related 'book_authors' entries
775 $c->stash->{object}->delete;
777 # Use 'flash' to save information across requests until it's read
778 $c->flash->{status_msg} = "Book deleted";
780 # Redirect the user back to the list page
781 $c->response->redirect($c->uri_for($self->action_for('list')));
784 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
785 flash vs. the C<status_msg> query parameter:
789 [%# Status and error messages %]
790 <span class="message">[% status_msg || c.flash.status_msg %]</span>
791 <span class="error">[% error_msg %]</span>
792 [%# This is where TT will stick all of your template's contents. -%]
794 </div><!-- end content -->
797 Although the sample above only shows the C<content> div, leave the
798 rest of the file intact -- the only change we made to the C<wrapper.tt2>
799 was to add "C<|| c.request.params.status_msg>" to the
800 C<E<lt>span class="message"E<gt>> line.
805 Restart the development server, log in, and then point your browser to
806 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
807 several books. Click the "Return to list" link and delete one of the
808 "Test" books you just added. The C<flash> mechanism should retain our
809 "Book deleted" status message across the redirect.
811 B<NOTE:> While C<flash> will save information across multiple requests,
812 I<it does get cleared the first time it is read>. In general, this is
813 exactly what you want -- the C<flash> message will get displayed on
814 the next screen where it's appropriate, but it won't "keep showing up"
815 after that first time (unless you reset it). Please refer to
816 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
820 =head2 Switch To Flash-To-Stash
822 Although the a use of flash above works well, the
823 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
824 alternative is to use the C<flash_to_stash> feature that automatically
825 copies the content of flash to stash. This makes your controller
826 and template code work regardless of where it was directly access, a
827 forward, or a redirect. To enable C<flash_to_stash>, you can either
828 set the value in C<lib/MyApp.pm> by changing the default
829 C<__PACKAGE__-E<gt>config> setting to something like:
833 session => {flash_to_stash => 1}
836 B<or> add the following to C<myapp.conf>:
842 The C<__PACKAGE__-E<gt>config> option is probably preferable here
843 since it's not something you will want to change at runtime without it
844 possibly breaking some of your code.
846 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
847 to match the following:
849 <span class="message">[% status_msg %]</span>
851 Restart the development server and go to
852 L<http://localhost:3000/books/list> in your browser. Delete another
853 of the "Test" books you added in the previous step. Flash should still
854 maintain the status message across the redirect even though you are no
855 longer explicitly accessing C<c.flash>.
860 Kennedy Clark, C<hkclark@gmail.com>
862 Please report any errors, issues or suggestions to the author. The
863 most recent version of the Catalyst Tutorial can be found at
864 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
866 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
867 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).