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 create=static dbi:SQLite:myapp.db
130 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
131 exists "/root/dev/MyApp/script/../t"
132 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
133 Schema dump completed.
134 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
136 $ ls lib/MyApp/Schema
137 Authors.pm BookAuthors.pm Books.pm Roles.pm UserRoles.pm Users.pm
139 Notice how the helper has added three new table-specific result source
140 files to the C<lib/MyApp/Schema/MyApp> directory. And, more
141 importantly, even if there were changes to the existing result source
142 files, those changes would have only been written above the C<# DO NOT
143 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-edited
144 enhancements would have been preserved.
146 Speaking of "hand-edit ted enhancements," we should now add
147 relationship information to the three new result source files. Edit
148 each of these files and add the following information between the C<#
149 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
151 C<lib/MyApp/Schema/Users.pm>:
159 # 1) Name of relationship, DBIC will create accessor with this name
160 # 2) Name of the model class referenced by this relationship
161 # 3) Column name in *foreign* table
162 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'user_id');
166 # 1) Name of relationship, DBIC will create accessor with this name
167 # 2) Name of has_many() relationship this many_to_many() is shortcut for
168 # 3) Name of belongs_to() relationship in model class of has_many() above
169 # You must already have the has_many() defined to use a many_to_many().
170 __PACKAGE__->many_to_many(roles => 'map_user_role', 'role');
173 C<lib/MyApp/Schema/Roles.pm>:
181 # 1) Name of relationship, DBIC will create accessor with this name
182 # 2) Name of the model class referenced by this relationship
183 # 3) Column name in *foreign* table
184 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'role_id');
187 C<lib/MyApp/Schema/UserRoles.pm>:
195 # 1) Name of relationship, DBIC will create accessor with this name
196 # 2) Name of the model class referenced by this relationship
197 # 3) Column name in *this* table
198 __PACKAGE__->belongs_to(user => 'MyApp::Schema::Users', 'user_id');
202 # 1) Name of relationship, DBIC will create accessor with this name
203 # 2) Name of the model class referenced by this relationship
204 # 3) Column name in *this* table
205 __PACKAGE__->belongs_to(role => 'MyApp::Schema::Roles', 'role_id');
208 The code for these three sets of updates is obviously very similar to
209 the edits we made to the C<Books>, C<Authors>, and C<BookAuthors>
210 classes created in Part 3.
212 Note that we do not need to make any change to the
213 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to
214 load all of the result class files it finds in below the
215 C<lib/MyApp/Schema> directory, so it will automatically pick
216 up our new table information.
219 =head2 Sanity-Check Reload of Development Server
221 We aren't ready to try out the authentication just yet; we only want
222 to do a quick check to be sure our model loads correctly. Press
223 C<Ctrl-C> to kill the previous server instance (if it's still running)
226 $ script/myapp_server.pl
228 Look for the three new model objects in the startup debug output:
231 .-------------------------------------------------------------------+----------.
233 +-------------------------------------------------------------------+----------+
234 | MyApp::Controller::Books | instance |
235 | MyApp::Controller::Root | instance |
236 | MyApp::Model::DB | instance |
237 | MyApp::Model::DB::Author | class |
238 | MyApp::Model::DB::Books | class |
239 | MyApp::Model::DB::BookAuthors | class |
240 | MyApp::Model::DB::Roles | class |
241 | MyApp::Model::DB::Users | class |
242 | MyApp::Model::DB::UserRoles | class |
243 | MyApp::View::TT | instance |
244 '-------------------------------------------------------------------+----------'
247 Again, notice that your "result class" classes have been "re-loaded"
248 by Catalyst under C<MyApp::Model>.
251 =head2 Include Authentication and Session Plugins
253 Edit C<lib/MyApp.pm> and update it as follows (everything below
254 C<StackTrace> is new):
256 __PACKAGE__->setup(qw/
266 Session::Store::FastMmap
267 Session::State::Cookie
270 B<Note:> As discussed in MoreCatalystBasics, different versions of
271 C<Catalyst::Devel> have used a variety of methods to load the plugins.
272 You can put the plugins in the C<use Catalyst> statement if you prefer.
274 The C<Authentication> plugin supports Authentication while the
275 C<Session> plugins are required to maintain state across multiple HTTP
278 Note that the only required Authentication class is the main one. This
279 is a change that occurred in version 0.09999_01 of the
280 C<Authentication> plugin. You B<do not need> to specify a particular
281 Authentication::Store or Authentication::Credential plugin. Instead,
282 indicate the Store and Credential you want to use in your application
283 configuration (see below).
285 Note that there are several options for
286 L<Session::Store|Catalyst::Plugin::Session::Store>
287 (L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap>
288 is generally a good choice if you are on Unix; try
289 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
290 are on Win32) -- consult
291 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
292 for additional information and options (for example to use a database-
293 backed session store).
296 =head2 Configure Authentication
298 Although C<__PACKAGE__-E<gt>config(name =E<gt> 'value');> is still
299 supported, newer Catalyst applications tend to place all configuration
300 information in C<myapp.conf> and automatically load this information
301 into C<MyApp-E<gt>config> using the
302 L<ConfigLoader|Catalyst::Plugin::ConfigLoader> plugin.
304 As discussed in Part 3 of the tutorial, Catalyst has recently
305 switched from a default config file format of YAML to
306 L<Config::General|Config::General> (an apache-like format). In case
307 you are using a version of Catalyst earlier than v5.7014, delete the
308 C<myapp.yml>, or convert it to .conf format using the TIP in
309 L<Catalyst::Manual::MoreCatalystBasics/EDIT THE LIST OF CATALYST PLUGINS>
310 then simply follow the directions below to create a new C<myapp.conf>
311 file. Although we will use the C<Config::General> format here because
312 YAML files can be difficult to cut and paste in certain environments,
313 you are free to use any format supported by
314 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
315 L<Config::Any|Config::Any> -- Catalyst will transparently handle the
318 Here, we need to load several parameters that tell
319 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
320 where to locate information in your database. To do this, edit the
321 C<myapp.conf> file and update it to match:
323 # rename this file to MyApp.yml and put a : in front of "name" if
324 # you want to use yaml like in old versions of Catalyst
331 # Note: this first definition would be the same as setting
332 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
333 # ->{credential} = 'Password' in lib/MyApp.pm
335 # Specify that we are going to do password-based auth
337 # This is the name of the field in the users table with the
338 # password stored in it
339 password_field password
340 # We are using an unencrypted password for now
344 # Use DBIC to retrieve username, password & role information
346 # This is the model object created by Catalyst::Model::DBIC
347 # from your schema (you created 'MyApp::Schema::User' but as
348 # the Catalyst startup debug messages show, it was loaded as
349 # 'MyApp::Model::DB::Users').
350 # NOTE: Omit 'MyApp::Model' here just as you would when using
351 # '$c->model("DB::Users)'
358 Inline comments in the code above explain how each field is being used.
361 =head2 Add Login and Logout Controllers
363 Use the Catalyst create script to create two stub controller files:
365 $ script/myapp_create.pl controller Login
366 $ script/myapp_create.pl controller Logout
368 You could easily use a single controller here. For example, you could
369 have a C<User> controller with both C<login> and C<logout> actions.
370 Remember, Catalyst is designed to be very flexible, and leaves such
371 matters up to you, the designer and programmer.
373 Then open C<lib/MyApp/Controller/Login.pm>, locate the
374 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
375 are using an older version of Catalyst) that was automatically
376 inserted by the helpers when we created the Login controller above,
377 and update the definition of C<sub index> to match:
385 sub index :Path :Args(0) {
388 # Get the username and password from form
389 my $username = $c->request->params->{username} || "";
390 my $password = $c->request->params->{password} || "";
392 # If the username and password values were found in form
393 if ($username && $password) {
394 # Attempt to log the user in
395 if ($c->authenticate({ username => $username,
396 password => $password } )) {
397 # If successful, then let them use the application
398 $c->response->redirect($c->uri_for(
399 $c->controller('Books')->action_for('list')));
402 # Set an error message
403 $c->stash->{error_msg} = "Bad username or password.";
407 # If either of above don't work out, send to the login page
408 $c->stash->{template} = 'login.tt2';
411 This controller fetches the C<username> and C<password> values from the
412 login form and attempts to authenticate the user. If successful, it
413 redirects the user to the book list page. If the login fails, the user
414 will stay at the login page and receive an error message. If the
415 C<username> and C<password> values are not present in the form, the
416 user will be taken to the empty login form.
418 Note that we could have used something like "C<sub default :Path>",
419 however, it is generally recommended (partly for historical reasons,
420 and partly for code clarity) only to use C<default> in
421 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
422 found page for the application.
424 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
425 specifically match the URL C</login>. C<Path> actions (aka, "literal
426 actions") create URI matches relative to the namespace of the
427 controller where they are defined. Although C<Path> supports
428 arguments that allow relative and absolute paths to be defined, here
429 we use an empty C<Path> definition to match on just the name of the
430 controller itself. The method name, C<index>, is arbitrary. We make
431 the match even more specific with the C<:Args(0)> action modifier --
432 this forces the match on I<only> C</login>, not
433 C</login/somethingelse>.
435 Next, update the corresponding method in
436 C<lib/MyApp/Controller/Logout.pm> to match:
444 sub index :Path :Args(0) {
447 # Clear the user's state
450 # Send the user to the starting point
451 $c->response->redirect($c->uri_for('/'));
454 As with the login controller, be sure to delete the
455 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
456 line of the C<sub index>.
459 =head2 Add a Login Form TT Template Page
461 Create a login form by opening C<root/src/login.tt2> and inserting:
463 [% META title = 'Login' %]
466 <form method="post" action="[% c.uri_for('/login') %]">
470 <td><input type="text" name="username" size="40" /></td>
474 <td><input type="password" name="password" size="40" /></td>
477 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
483 =head2 Add Valid User Check
485 We need something that provides enforcement for the authentication
486 mechanism -- a I<global> mechanism that prevents users who have not
487 passed authentication from reaching any pages except the login page.
488 This is generally done via an C<auto> action/method (prior to Catalyst
489 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
490 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
492 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
493 the following method:
497 Check if there is a user and, if not, forward to login page
501 # Note that 'auto' runs after 'begin' but before your actions and that
502 # 'auto's "chain" (all from application path to most specific class are run)
503 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
507 # Allow unauthenticated users to reach the login page. This
508 # allows unauthenticated users to reach any action in the Login
509 # controller. To lock it down to a single action, we could use:
510 # if ($c->action eq $c->controller('Login')->action_for('index'))
511 # to only allow unauthenticated access to the 'index' action we
513 if ($c->controller eq $c->controller('Login')) {
517 # If a user doesn't exist, force login
518 if (!$c->user_exists) {
519 # Dump a log message to the development server debug output
520 $c->log->debug('***Root::auto User not found, forwarding to /login');
521 # Redirect the user to the login page
522 $c->response->redirect($c->uri_for('/login'));
523 # Return 0 to cancel 'post-auto' processing and prevent use of application
527 # User found, so return 1 to continue with processing after this 'auto'
532 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
533 every C<auto> method from the application/root controller down to the
534 most specific controller will be called. By placing the
535 authentication enforcement code inside the C<auto> method of
536 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
537 called for I<every> request that is received by the entire
541 =head2 Displaying Content Only to Authenticated Users
543 Let's say you want to provide some information on the login page that
544 changes depending on whether the user has authenticated yet. To do
545 this, open C<root/src/login.tt2> in your editor and add the following
546 lines to the bottom of the file:
550 # This code illustrates how certain parts of the TT
551 # template will only be shown to users who have logged in
553 [% IF c.user_exists %]
554 Please Note: You are already logged in as '[% c.user.username %]'.
555 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
557 You need to log in to use this application.
560 Note that this whole block is a comment because the "#" appears
561 immediate after the "[%" (with no spaces in between). Although it
562 can be a handy way to temporarily "comment out" a whole block of
563 TT code, it's probably a little too subtle for use in "normal"
568 Although most of the code is comments, the middle few lines provide a
569 "you are already logged in" reminder if the user returns to the login
570 page after they have already authenticated. For users who have not yet
571 authenticated, a "You need to log in..." message is displayed (note the
572 use of an IF-THEN-ELSE construct in TT).
575 =head2 Try Out Authentication
577 Press C<Ctrl-C> to kill the previous server instance (if it's still
578 running) and restart it:
580 $ script/myapp_server.pl
582 B<IMPORTANT NOTE:> If you are having issues with authentication on
583 Internet Explorer, be sure to check the system clocks on both your
584 server and client machines. Internet Explorer is very picky about
585 timestamps for cookies. You can quickly sync an Ubuntu system with
586 the following command:
588 sudo ntpdate ntp.ubuntu.com
590 Or possibly try C<sudo ntpdate -u ntp.ubuntu.com> (to us an
591 unpriviledged port) or C<sudo ntpdate pool.ntp.org> (to try a
592 different server in case the Ubuntu NTP server is down).
594 Now trying going to L<http://localhost:3000/books/list> and you should
595 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
596 if necessary (the "You are already logged in" message should I<not>
597 appear -- if it does, click the C<logout> button and try again). Note
598 the C<***Root::auto User not found...> debug message in the
599 development server output. Enter username C<test01> and password
600 C<mypass>, and you should be taken to the Book List page.
602 Open C<root/src/books/list.tt2> and add the following lines to the
603 bottom (below the closing </table> tag):
606 <a href="[% c.uri_for('/login') %]">Login</a>
607 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
610 Reload your browser and you should now see a "Login" and "Create" links
611 at the bottom of the page (as mentioned earlier, you can update template
612 files without reloading the development server). Click the first link
613 to return to the login page. This time you I<should> see the "You are
614 already logged in" message.
616 Finally, click the C<You can logout here> link on the C</login> page.
617 You should stay at the login page, but the message should change to "You
618 need to log in to use this application."
621 =head1 USING PASSWORD HASHES
623 In this section we increase the security of our system by converting
624 from cleartext passwords to SHA-1 password hashes.
626 B<Note:> This section is optional. You can skip it and the rest of the
627 tutorial will function normally.
629 Be aware that even with the techniques shown in this section, the browser
630 still transmits the passwords in cleartext to your application. We are
631 just avoiding the I<storage> of cleartext passwords in the database by
632 using a SHA-1 hash. If you are concerned about cleartext passwords
633 between the browser and your application, consider using SSL/TLS, made
634 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL. You should
635 also consider adding a "salt" mechanism to your hashed passwords to
636 mitigate the risk of a "rainbow table" crack against your passwords (see
637 L<Catalyst::Authentication::Credential::Password|Catalyst::Authentication::Credential::Password>
638 for more information on using a salt value).
641 =head2 Get a SHA-1 Hash for the Password
643 Catalyst uses the C<Digest> module to support a variety of hashing
644 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
645 First, we should compute the SHA-1 hash for the "mypass" password we are
646 using. The following command-line Perl script provides a "quick and
647 dirty" way to do this:
649 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
650 e727d1464ae12436e899a726da5b2f11d8381b26
653 B<Note:> If you are following along in Ubuntu, you will need to install
654 C<Digest::SHA> with the following command to run the example code above:
656 sudo aptitude install libdigest-sha-perl
658 B<Note:> You should probably modify this code for production use to
659 not read the password from the command line. By having the script
660 prompt for the cleartext password, it avoids having the password linger
661 in forms such as your C<.bash_history> files (assuming you are using
662 BASH as your shell). An example of such a script can be found in
666 =head2 Switch to SHA-1 Password Hashes in the Database
668 Next, we need to change the C<password> column of our C<users> table to
669 store this hash value vs. the existing cleartext password. Open
670 C<myapp03.sql> in your editor and enter:
673 -- Convert passwords to SHA-1 hashes
675 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
676 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
677 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
679 Then use the following command to update the SQLite database:
681 $ sqlite3 myapp.db < myapp03.sql
683 B<Note:> We are using SHA-1 hashes here, but many other hashing
684 algorithms are supported. See C<Digest> for more information.
687 =head2 Enable SHA-1 Hash Passwords in
688 C<Catalyst::Plugin::Authentication::Store::DBIC>
690 Edit C<myapp.conf> and update it to match (the C<password_type> and
691 C<password_hash_type> are new, everything else is the same):
693 # rename this file to MyApp.yml and put a : in front of "name" if
694 # you want to use yaml like in old versions of Catalyst
701 # Note this first definition would be the same as setting
702 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
703 # ->{credential} = 'Password' in lib/MyApp.pm
705 # Specify that we are going to do password-based auth
707 # This is the name of the field in the users table with the
708 # password stored in it
709 password_field password
710 # Switch to more secure hashed passwords
712 # Use the SHA-1 hashing algorithm
713 password_hash_type SHA-1
716 # Use DBIC to retrieve username, password & role information
718 # This is the model object created by Catalyst::Model::DBIC
719 # from your schema (you created 'MyApp::Schema::User' but as
720 # the Catalyst startup debug messages show, it was loaded as
721 # 'MyApp::Model::DB::Users').
722 # NOTE: Omit 'MyApp::Model' here just as you would when using
723 # '$c->model("DB::Users)'
731 =head2 Try Out the Hashed Passwords
733 Press C<Ctrl-C> to kill the previous server instance (if it's still
734 running) and restart it:
736 $ script/myapp_server.pl
738 You should now be able to go to L<http://localhost:3000/books/list> and
739 login as before. When done, click the "logout" link on the login page
740 (or point your browser at L<http://localhost:3000/logout>).
743 =head1 USING THE SESSION FOR FLASH
745 As discussed in Part 3 of the tutorial, C<flash> allows you to set
746 variables in a way that is very similar to C<stash>, but it will
747 remain set across multiple requests. Once the value is read, it
748 is cleared (unless reset). Although C<flash> has nothing to do with
749 authentication, it does leverage the same session plugins. Now that
750 those plugins are enabled, let's go back and update the "delete
751 and redirect with query parameters" code seen at the end of the
752 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
753 tutorial to take advantage of C<flash>.
755 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
756 to match the following (everything after the model search line of code
765 sub delete :Chained('object') :PathPart('delete') :Args(0) {
768 # Use the book object saved by 'object' and delete it along
769 # with related 'book_authors' entries
770 $c->stash->{object}->delete;
772 # Use 'flash' to save information across requests until it's read
773 $c->flash->{status_msg} = "Book deleted";
775 # Redirect the user back to the list page
776 $c->response->redirect($c->uri_for($self->action_for('list')));
779 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
780 flash vs. the C<status_msg> query parameter:
784 [%# Status and error messages %]
785 <span class="message">[% status_msg || c.flash.status_msg %]</span>
786 <span class="error">[% error_msg %]</span>
787 [%# This is where TT will stick all of your template's contents. -%]
789 </div><!-- end content -->
792 Although the sample above only shows the C<content> div, leave the
793 rest of the file intact -- the only change we made to the C<wrapper.tt2>
794 was to add "C<|| c.request.params.status_msg>" to the
795 C<E<lt>span class="message"E<gt>> line.
800 Restart the development server, log in, and then point your browser to
801 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
802 several books. Click the "Return to list" link and delete one of the
803 "Test" books you just added. The C<flash> mechanism should retain our
804 "Book deleted" status message across the redirect.
806 B<NOTE:> While C<flash> will save information across multiple requests,
807 I<it does get cleared the first time it is read>. In general, this is
808 exactly what you want -- the C<flash> message will get displayed on
809 the next screen where it's appropriate, but it won't "keep showing up"
810 after that first time (unless you reset it). Please refer to
811 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
815 =head2 Switch To Flash-To-Stash
817 Although the a use of flash above works well, the
818 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
819 alternative is to use the C<flash_to_stash> feature that automatically
820 copies the content of flash to stash. This makes your controller
821 and template code work regardless of where it was directly access, a
822 forward, or a redirect. To enable C<flash_to_stash>, you can either
823 set the value in C<lib/MyApp.pm> by changing the default
824 C<__PACKAGE__-E<gt>config> setting to something like:
828 session => {flash_to_stash => 1}
831 B<or> add the following to C<myapp.conf>:
837 The C<__PACKAGE__-E<gt>config> option is probably preferable here
838 since it's not something you will want to change at runtime without it
839 possibly breaking some of your code.
841 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
842 to match the following:
844 <span class="message">[% status_msg %]</span>
846 Restart the development server and go to
847 L<http://localhost:3000/books/list> in your browser. Delete another
848 of the "Test" books you added in the previous step. Flash should still
849 maintain the status message across the redirect even though you are no
850 longer explicitly accessing C<c.flash>.
855 Kennedy Clark, C<hkclark@gmail.com>
857 Please report any errors, issues or suggestions to the author. The
858 most recent version of the Catalyst Tutorial can be found at
859 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
861 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
862 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).