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>.
70 =head1 BASIC AUTHENTICATION
72 This section explores how to add authentication logic to a Catalyst
76 =head2 Add Users and Roles to the Database
78 First, we add both user and role information to the database (we will
79 add the role information here although it will not be used until the
80 authorization section, Part 6). Create a new SQL script file by opening
81 C<myapp02.sql> in your editor and insert:
84 -- Add users and roles tables, along with a many-to-many join table
87 id INTEGER PRIMARY KEY,
96 id INTEGER PRIMARY KEY,
99 CREATE TABLE user_roles (
102 PRIMARY KEY (user_id, role_id)
105 -- Load up some initial test data
107 INSERT INTO users VALUES (1, 'test01', 'mypass', 't01@na.com', 'Joe', 'Blow', 1);
108 INSERT INTO users VALUES (2, 'test02', 'mypass', 't02@na.com', 'Jane', 'Doe', 1);
109 INSERT INTO users VALUES (3, 'test03', 'mypass', 't03@na.com', 'No', 'Go', 0);
110 INSERT INTO roles VALUES (1, 'user');
111 INSERT INTO roles VALUES (2, 'admin');
112 INSERT INTO user_roles VALUES (1, 1);
113 INSERT INTO user_roles VALUES (1, 2);
114 INSERT INTO user_roles VALUES (2, 1);
115 INSERT INTO user_roles VALUES (3, 1);
117 Then load this into the C<myapp.db> database with the following command:
119 $ sqlite3 myapp.db < myapp02.sql
122 =head2 Add User and Role Information to DBIC Schema
124 Although we could manually edit the DBIC schema information to include
125 the new tables added in the previous step, let's use the C<create=static>
126 option on the DBIC model helper to do most of the work for us:
128 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db
129 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
130 exists "/root/dev/MyApp/script/../t"
131 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
132 Schema dump completed.
133 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
135 $ ls lib/MyApp/Schema
136 Authors.pm BookAuthors.pm Books.pm Roles.pm UserRoles.pm Users.pm
138 Notice how the helper has added three new table-specific result source
139 files to the C<lib/MyApp/Schema/MyApp> directory. And, more
140 importantly, even if there were changes to the existing result source
141 files, those changes would have only been written above the C<# DO NOT
142 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-edited
143 enhancements would have been preserved.
145 Speaking of "hand-edit ted enhancements," we should now add
146 relationship information to the three new result source files. Edit
147 each of these files and add the following information between the C<#
148 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
150 C<lib/MyApp/Schema/Users.pm>:
158 # 1) Name of relationship, DBIC will create accessor with this name
159 # 2) Name of the model class referenced by this relationship
160 # 3) Column name in *foreign* table
161 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'user_id');
165 # 1) Name of relationship, DBIC will create accessor with this name
166 # 2) Name of has_many() relationship this many_to_many() is shortcut for
167 # 3) Name of belongs_to() relationship in model class of has_many() above
168 # You must already have the has_many() defined to use a many_to_many().
169 __PACKAGE__->many_to_many(roles => 'map_user_role', 'role');
172 C<lib/MyApp/Schema/Roles.pm>:
180 # 1) Name of relationship, DBIC will create accessor with this name
181 # 2) Name of the model class referenced by this relationship
182 # 3) Column name in *foreign* table
183 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'role_id');
186 C<lib/MyApp/Schema/UserRoles.pm>:
194 # 1) Name of relationship, DBIC will create accessor with this name
195 # 2) Name of the model class referenced by this relationship
196 # 3) Column name in *this* table
197 __PACKAGE__->belongs_to(user => 'MyApp::Schema::Users', 'user_id');
201 # 1) Name of relationship, DBIC will create accessor with this name
202 # 2) Name of the model class referenced by this relationship
203 # 3) Column name in *this* table
204 __PACKAGE__->belongs_to(role => 'MyApp::Schema::Roles', 'role_id');
207 The code for these three sets of updates is obviously very similar to
208 the edits we made to the C<Books>, C<Authors>, and C<BookAuthors>
209 classes created in Part 3.
211 Note that we do not need to make any change to the
212 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to
213 load all of the result class files it finds in below the
214 C<lib/MyApp/Schema> directory, so it will automatically pick
215 up our new table information.
218 =head2 Sanity-Check Reload of Development Server
220 We aren't ready to try out the authentication just yet; we only want
221 to do a quick check to be sure our model loads correctly. Press
222 C<Ctrl-C> to kill the previous server instance (if it's still running)
225 $ script/myapp_server.pl
227 Look for the three new model objects in the startup debug output:
230 .-------------------------------------------------------------------+----------.
232 +-------------------------------------------------------------------+----------+
233 | MyApp::Controller::Books | instance |
234 | MyApp::Controller::Root | instance |
235 | MyApp::Model::DB | instance |
236 | MyApp::Model::DB::Author | class |
237 | MyApp::Model::DB::Books | class |
238 | MyApp::Model::DB::BookAuthors | class |
239 | MyApp::Model::DB::Roles | class |
240 | MyApp::Model::DB::Users | class |
241 | MyApp::Model::DB::UserRoles | class |
242 | MyApp::View::TT | instance |
243 '-------------------------------------------------------------------+----------'
246 Again, notice that your "result class" classes have been "re-loaded"
247 by Catalyst under C<MyApp::Model>.
250 =head2 Include Authentication and Session Plugins
252 Edit C<lib/MyApp.pm> and update it as follows (everything below
253 C<StackTrace> is new):
255 __PACKAGE__->setup(qw/
265 Session::Store::FastMmap
266 Session::State::Cookie
269 B<Note:> As discussed in MoreCatalystBasics, different versions of
270 C<Catalyst::Devel> have used a variety of methods to load the plugins.
271 You can put the plugins in the C<use Catalyst> statement if you prefer.
273 The C<Authentication> plugin supports Authentication while the
274 C<Session> plugins are required to maintain state across multiple HTTP
277 Note that the only required Authentication class is the main one. This
278 is a change that occurred in version 0.09999_01 of the
279 C<Authentication> plugin. You B<do not need> to specify a particular
280 Authentication::Store or Authentication::Credential plugin. Instead,
281 indicate the Store and Credential you want to use in your application
282 configuration (see below).
284 Note that there are several options for
285 L<Session::Store|Catalyst::Plugin::Session::Store>
286 (L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap>
287 is generally a good choice if you are on Unix; try
288 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
289 are on Win32) -- consult
290 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
291 for additional information and options (for example to use a database-
292 backed session store).
295 =head2 Configure Authentication
297 Although C<__PACKAGE__-E<gt>config(name =E<gt> 'value');> is still
298 supported, newer Catalyst applications tend to place all configuration
299 information in C<myapp.conf> and automatically load this information
300 into C<MyApp-E<gt>config> using the
301 L<ConfigLoader|Catalyst::Plugin::ConfigLoader> plugin.
303 First, as noted in Part 3 of the tutorial, Catalyst has recently
304 switched from a default config file format of YAML to
305 C<Config::General> (an apache-like format). In case you are using a
306 version of Catalyst earlier than v5.7014, delete the C<myapp.yml>, or
307 convert it to .conf format using the TIP in
308 L<Catalyst::Manual::MoreCatalystBasics>; then simply follow the
309 directions below to create a new C<myapp.conf> file.
311 Here, we need to load several parameters that tell
312 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
313 where to locate information in your database. To do this, edit the
314 C<myapp.conf> file and update it to match:
316 # rename this file to MyApp.yml and put a : in front of "name" if
317 # you want to use yaml like in old versions of Catalyst
324 # Note: this first definition would be the same as setting
325 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
326 # ->{credential} = 'Password' in lib/MyApp.pm
328 # Specify that we are going to do password-based auth
330 # This is the name of the field in the users table with the
331 # password stored in it
332 password_field password
333 # We are using an unencrypted password for now
337 # Use DBIC to retrieve username, password & role information
339 # This is the model object created by Catalyst::Model::DBIC
340 # from your schema (you created 'MyApp::Schema::User' but as
341 # the Catalyst startup debug messages show, it was loaded as
342 # 'MyApp::Model::DB::Users').
343 # NOTE: Omit 'MyApp::Model' here just as you would when using
344 # '$c->model("DB::Users)'
351 Inline comments in the code above explain how each field is being used.
353 Note that you can use many other config file formats with catalyst.
354 See L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
358 =head2 Add Login and Logout Controllers
360 Use the Catalyst create script to create two stub controller files:
362 $ script/myapp_create.pl controller Login
363 $ script/myapp_create.pl controller Logout
365 B<NOTE:> You could easily use a single controller here. For example,
366 you could have a C<User> controller with both C<login> and C<logout>
367 actions. Remember, Catalyst is designed to be very flexible, and leaves
368 such matters up to you, the designer and programmer.
370 Then open C<lib/MyApp/Controller/Login.pm>, locate the C<sub index
371 :Path :Args(0)> method (or C<sub index : Private> if you are using an
372 older version of Catalyst) that was automatically inserted by the
373 helpers when we created the Login controller above, and update the
374 definition of C<sub index> to match:
382 sub index :Path :Args(0) {
385 # Get the username and password from form
386 my $username = $c->request->params->{username} || "";
387 my $password = $c->request->params->{password} || "";
389 # If the username and password values were found in form
390 if ($username && $password) {
391 # Attempt to log the user in
392 if ($c->authenticate({ username => $username,
393 password => $password } )) {
394 # If successful, then let them use the application
395 $c->response->redirect($c->uri_for(
396 $c->controller('Books')->action_for('list')));
399 # Set an error message
400 $c->stash->{error_msg} = "Bad username or password.";
404 # If either of above don't work out, send to the login page
405 $c->stash->{template} = 'login.tt2';
408 This controller fetches the C<username> and C<password> values from the
409 login form and attempts to authenticate the user. If successful, it
410 redirects the user to the book list page. If the login fails, the user
411 will stay at the login page and receive an error message. If the
412 C<username> and C<password> values are not present in the form, the
413 user will be taken to the empty login form.
415 Note that we could have used something like C<sub default :Path>,
416 however, it is generally recommended (partly for historical reasons,
417 and partly for code clarity) only to use C<default> in
418 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
419 found page for the application.
421 Instead, we are using C<sub somename :Path :Args(0) {...}> here to
422 specifically match the URL C</login>. C<Path> actions (aka, "literal
423 actions") create URI matches relative to the namespace of the
424 controller where they are defined. Although C<Path> supports
425 arguments that allow relative and absolute paths to be defined, here
426 we use an empty C<Path> definition to match on just the name of the
427 controller itself. The method name, C<index>, is arbitrary. We make
428 the match even more specific with the C<:Args(0)> action modifier --
429 this forces the match on I<only> C</login>, not
430 C</login/somethingelse>.
432 Next, update the corresponding method in
433 C<lib/MyApp/Controller/Logout.pm> to match:
441 sub index :Path :Args(0) {
444 # Clear the user's state
447 # Send the user to the starting point
448 $c->response->redirect($c->uri_for('/'));
451 As with the login controller, be sure to delete the
452 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
453 line of the C<sub index>.
456 =head2 Add a Login Form TT Template Page
458 Create a login form by opening C<root/src/login.tt2> and inserting:
460 [% META title = 'Login' %]
463 <form method="post" action="[% c.uri_for('/login') %]">
467 <td><input type="text" name="username" size="40" /></td>
471 <td><input type="password" name="password" size="40" /></td>
474 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
480 =head2 Add Valid User Check
482 We need something that provides enforcement for the authentication
483 mechanism -- a I<global> mechanism that prevents users who have not
484 passed authentication from reaching any pages except the login page.
485 This is generally done via an C<auto> action/method (prior to Catalyst
486 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
487 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
489 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
490 the following method:
494 Check if there is a user and, if not, forward to login page
498 # Note that 'auto' runs after 'begin' but before your actions and that
499 # 'auto's "chain" (all from application path to most specific class are run)
500 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
504 # Allow unauthenticated users to reach the login page. This
505 # allows unauthenticated users to reach any action in the Login
506 # controller. To lock it down to a single action, we could use:
507 # if ($c->action eq $c->controller('Login')->action_for('index'))
508 # to only allow unauthenticated access to the 'index' action we
510 if ($c->controller eq $c->controller('Login')) {
514 # If a user doesn't exist, force login
515 if (!$c->user_exists) {
516 # Dump a log message to the development server debug output
517 $c->log->debug('***Root::auto User not found, forwarding to /login');
518 # Redirect the user to the login page
519 $c->response->redirect($c->uri_for('/login'));
520 # Return 0 to cancel 'post-auto' processing and prevent use of application
524 # User found, so return 1 to continue with processing after this 'auto'
529 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
530 every C<auto> method from the application/root controller down to the
531 most specific controller will be called. By placing the
532 authentication enforcement code inside the C<auto> method of
533 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
534 called for I<every> request that is received by the entire
538 =head2 Displaying Content Only to Authenticated Users
540 Let's say you want to provide some information on the login page that
541 changes depending on whether the user has authenticated yet. To do
542 this, open C<root/src/login.tt2> in your editor and add the following
543 lines to the bottom of the file:
547 # This code illustrates how certain parts of the TT
548 # template will only be shown to users who have logged in
550 [% IF c.user_exists %]
551 Please Note: You are already logged in as '[% c.user.username %]'.
552 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
554 You need to log in to use this application.
557 Note that this whole block is a comment because the "#" appears
558 immediate after the "[%" (with no spaces in between). Although it
559 can be a handy way to temporarily "comment out" a whole block of
560 TT code, it's probably a little too subtle for use in "normal"
565 Although most of the code is comments, the middle few lines provide a
566 "you are already logged in" reminder if the user returns to the login
567 page after they have already authenticated. For users who have not yet
568 authenticated, a "You need to log in..." message is displayed (note the
569 use of an IF-THEN-ELSE construct in TT).
572 =head2 Try Out Authentication
574 Press C<Ctrl-C> to kill the previous server instance (if it's still
575 running) and restart it:
577 $ script/myapp_server.pl
579 B<IMPORTANT NOTE:> If you are having issues with authentication on
580 Internet Explorer, be sure to check the system clocks on both your
581 server and client machines. Internet Explorer is very picky about
582 timestamps for cookies. Note that you can quickly sync an Ubuntu
583 system with the following command:
585 sudo ntpdate ntp.ubuntu.com
587 Or possibly try C<sudo ntpdate -u ntp.ubuntu.com> (to us an
588 unpriviledged port) or C<sudo ntpdate pool.ntp.org> (to try a
589 different server in case the Ubuntu NTP server is down).
591 Now trying going to L<http://localhost:3000/books/list> and you should
592 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
593 if necessary (the "You are already logged in" message should I<not>
594 appear -- if it does, click the C<logout> button and try again). Note
595 the C<***Root::auto User not found...> debug message in the
596 development server output. Enter username C<test01> and password
597 C<mypass>, and you should be taken to the Book List page.
599 Open C<root/src/books/list.tt2> and add the following lines to the
600 bottom (below the closing </table> tag):
603 <a href="[% c.uri_for('/login') %]">Login</a>
604 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
607 Reload your browser and you should now see a "Login" and "Create" links
608 at the bottom of the page (as mentioned earlier, you can update template
609 files without reloading the development server). Click the first link
610 to return to the login page. This time you I<should> see the "You are
611 already logged in" message.
613 Finally, click the C<You can logout here> link on the C</login> page.
614 You should stay at the login page, but the message should change to "You
615 need to log in to use this application."
618 =head1 USING PASSWORD HASHES
620 In this section we increase the security of our system by converting
621 from cleartext passwords to SHA-1 password hashes.
623 B<Note:> This section is optional. You can skip it and the rest of the
624 tutorial will function normally.
626 Note that even with the techniques shown in this section, the browser
627 still transmits the passwords in cleartext to your application. We are
628 just avoiding the I<storage> of cleartext passwords in the database by
629 using a SHA-1 hash. If you are concerned about cleartext passwords
630 between the browser and your application, consider using SSL/TLS, made
631 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
634 =head2 Get a SHA-1 Hash for the Password
636 Catalyst uses the C<Digest> module to support a variety of hashing
637 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
638 First, we should compute the SHA-1 hash for the "mypass" password we are
639 using. The following command-line Perl script provides a "quick and
640 dirty" way to do this:
642 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
643 e727d1464ae12436e899a726da5b2f11d8381b26
646 B<Note:> If you are following along in Ubuntu, you will need to install
647 C<Digest::SHA> with the following command to run the example code above:
649 sudo aptitude install libdigest-sha-perl
651 B<Note:> You should probably modify this code for production use to
652 not read the password from the command line. By having the script
653 prompt for the cleartext password, it avoids having the password linger
654 in forms such as your C<.bash_history> files (assuming you are using
655 BASH as your shell). An example of such a script can be found in
659 =head2 Switch to SHA-1 Password Hashes in the Database
661 Next, we need to change the C<password> column of our C<users> table to
662 store this hash value vs. the existing cleartext password. Open
663 C<myapp03.sql> in your editor and enter:
666 -- Convert passwords to SHA-1 hashes
668 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
669 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
670 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
672 Then use the following command to update the SQLite database:
674 $ sqlite3 myapp.db < myapp03.sql
676 B<Note:> We are using SHA-1 hashes here, but many other hashing
677 algorithms are supported. See C<Digest> for more information.
680 =head2 Enable SHA-1 Hash Passwords in
681 C<Catalyst::Plugin::Authentication::Store::DBIC>
683 Edit C<myapp.conf> and update it to match (the C<password_type> and
684 C<password_hash_type> are new, everything else is the same):
686 # rename this file to MyApp.yml and put a : in front of "name" if
687 # you want to use yaml like in old versions of Catalyst
694 # Note this first definition would be the same as setting
695 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
696 # ->{credential} = 'Password' in lib/MyApp.pm
698 # Specify that we are going to do password-based auth
700 # This is the name of the field in the users table with the
701 # password stored in it
702 password_field password
703 # Switch to more secure hashed passwords
705 # Use the SHA-1 hashing algorithm
706 password_hash_type SHA-1
709 # Use DBIC to retrieve username, password & role information
711 # This is the model object created by Catalyst::Model::DBIC
712 # from your schema (you created 'MyApp::Schema::User' but as
713 # the Catalyst startup debug messages show, it was loaded as
714 # 'MyApp::Model::DB::Users').
715 # NOTE: Omit 'MyApp::Model' here just as you would when using
716 # '$c->model("DB::Users)'
724 =head2 Try Out the Hashed Passwords
726 Press C<Ctrl-C> to kill the previous server instance (if it's still
727 running) and restart it:
729 $ script/myapp_server.pl
731 You should now be able to go to L<http://localhost:3000/books/list> and
732 login as before. When done, click the "Logout" link on the login page
733 (or point your browser at L<http://localhost:3000/logout>).
736 =head1 USING THE SESSION FOR FLASH
738 As discussed in Part 3 of the tutorial, C<flash> allows you to set
739 variables in a way that is very similar to C<stash>, but it will
740 remain set across multiple requests. Once the value is read, it
741 is cleared (unless reset). Although C<flash> has nothing to do with
742 authentication, it does leverage the same session plugins. Now that
743 those plugins are enabled, let's go back and improve the "delete
744 and redirect with query parameters" code seen at the end of the
745 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
748 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
749 to match the following (everything after the model search line of code
759 # $id = primary key of book to delete
760 my ($self, $c, $id) = @_;
762 # Search for the book and then delete it
763 $c->model('DB::Books')->search({id => $id})->delete_all;
765 # Use 'flash' to save information across requests until it's read
766 $c->flash->{status_msg} = "Book deleted";
768 # Redirect the user back to the list page
769 $c->response->redirect($c->uri_for($self->action_for('list')));
772 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
773 flash vs. the C<status_msg> query parameter:
777 [%# Status and error messages %]
778 <span class="message">[% status_msg || c.flash.status_msg %]</span>
779 <span class="error">[% error_msg %]</span>
780 [%# This is where TT will stick all of your template's contents. -%]
782 </div><!-- end content -->
785 Although the sample above only shows the C<content> div, leave the
786 rest of the file intact -- the only change we made to the C<wrapper.tt2>
787 was to add "C<|| c.request.params.status_msg>" to the
788 C<E<lt>span class="message"E<gt>> line.
793 Restart the development server and point your browser to
794 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
795 several books. Click the "Return to list" link and delete one of the
796 "Test" books you just added. The C<flash> mechanism should retain our
797 "Book deleted" status message across the redirect.
799 B<NOTE:> While C<flash> will save information across multiple requests,
800 I<it does get cleared the first time it is read>. In general, this is
801 exactly what you want -- the C<flash> message will get displayed on
802 the next screen where it's appropriate, but it won't "keep showing up"
803 after that first time (unless you reset it). Please refer to
804 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
808 =head2 Switch To Flash-To-Stash
810 Although the a use of flash above is certainly an improvement over the
811 C<status_msg> we employed in Part 4 of the tutorial, the
812 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
813 alternative is to use the C<flash_to_stash> feature that automatically
814 copies the content of flash to stash. This makes your controller
815 and template code work regardless of where it was directly access, a
816 forward, or a redirect. To enable C<flash_to_stash>, you can either
817 set the value in C<lib/MyApp.pm> by changing the default
818 C<__PACKAGE__-E<gt>config> setting to something like:
822 session => {flash_to_stash => 1}
825 B<or> add the following to C<myapp.conf>:
831 The C<__PACKAGE__-E<gt>config> option is probably preferable here
832 since it's not something you will want to change at runtime without it
833 possibly breaking some of your code.
835 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
836 to match the following:
838 <span class="message">[% status_msg %]</span>
840 Restart the development server and go to
841 L<http://localhost:3000/books/list> in your browser. Delete another
842 of the "Test" books you added in the previous step. Flash should still
843 maintain the status message across the redirect even though you are no
844 longer explicitly accessing C<c.flash>.
849 Kennedy Clark, C<hkclark@gmail.com>
851 Please report any errors, issues or suggestions to the author. The
852 most recent version of the Catalyst Tutorial can be found at
853 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
855 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
856 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).