3 Catalyst::Manual::Tutorial::Authentication - Catalyst Tutorial - Chapter 5: Authentication
8 This is B<Chapter 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 chapter 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, Chapter 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 Chapter 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 There are a variety of way to provide configuration information to
300 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>.
302 L<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
303 because it automatically sets a reasonable set of defaults for us. Open
304 C<lib/MyApp.pm> and place the following text above the call to
305 C<__PACKAGE__-E<gt>setup();>:
307 # Configure SimpleDB Authentication
308 __PACKAGE__->config->{'Plugin::Authentication'} = {
311 user_model => 'DB::Users',
312 password_type => 'clear',
316 We could have placed this configuration in C<myapp.conf>, but placing
317 it in C<lib/MyApp.pm> is probably a better place since it's not likely
318 something that users of your application will want to change during
322 =head2 Add Login and Logout Controllers
324 Use the Catalyst create script to create two stub controller files:
326 $ script/myapp_create.pl controller Login
327 $ script/myapp_create.pl controller Logout
329 You could easily use a single controller here. For example, you could
330 have a C<User> controller with both C<login> and C<logout> actions.
331 Remember, Catalyst is designed to be very flexible, and leaves such
332 matters up to you, the designer and programmer.
334 Then open C<lib/MyApp/Controller/Login.pm>, locate the
335 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
336 are using an older version of Catalyst) that was automatically
337 inserted by the helpers when we created the Login controller above,
338 and update the definition of C<sub index> to match:
346 sub index :Path :Args(0) {
349 # Get the username and password from form
350 my $username = $c->request->params->{username} || "";
351 my $password = $c->request->params->{password} || "";
353 # If the username and password values were found in form
354 if ($username && $password) {
355 # Attempt to log the user in
356 if ($c->authenticate({ username => $username,
357 password => $password } )) {
358 # If successful, then let them use the application
359 $c->response->redirect($c->uri_for(
360 $c->controller('Books')->action_for('list')));
363 # Set an error message
364 $c->stash->{error_msg} = "Bad username or password.";
368 # If either of above don't work out, send to the login page
369 $c->stash->{template} = 'login.tt2';
372 This controller fetches the C<username> and C<password> values from the
373 login form and attempts to authenticate the user. If successful, it
374 redirects the user to the book list page. If the login fails, the user
375 will stay at the login page and receive an error message. If the
376 C<username> and C<password> values are not present in the form, the
377 user will be taken to the empty login form.
379 Note that we could have used something like "C<sub default :Path>",
380 however, it is generally recommended (partly for historical reasons,
381 and partly for code clarity) only to use C<default> in
382 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
383 found page for the application.
385 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
386 specifically match the URL C</login>. C<Path> actions (aka, "literal
387 actions") create URI matches relative to the namespace of the
388 controller where they are defined. Although C<Path> supports
389 arguments that allow relative and absolute paths to be defined, here
390 we use an empty C<Path> definition to match on just the name of the
391 controller itself. The method name, C<index>, is arbitrary. We make
392 the match even more specific with the C<:Args(0)> action modifier --
393 this forces the match on I<only> C</login>, not
394 C</login/somethingelse>.
396 Next, update the corresponding method in
397 C<lib/MyApp/Controller/Logout.pm> to match:
405 sub index :Path :Args(0) {
408 # Clear the user's state
411 # Send the user to the starting point
412 $c->response->redirect($c->uri_for('/'));
415 As with the login controller, be sure to delete the
416 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
417 line of the C<sub index>.
420 =head2 Add a Login Form TT Template Page
422 Create a login form by opening C<root/src/login.tt2> and inserting:
424 [% META title = 'Login' %]
427 <form method="post" action="[% c.uri_for('/login') %]">
431 <td><input type="text" name="username" size="40" /></td>
435 <td><input type="password" name="password" size="40" /></td>
438 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
444 =head2 Add Valid User Check
446 We need something that provides enforcement for the authentication
447 mechanism -- a I<global> mechanism that prevents users who have not
448 passed authentication from reaching any pages except the login page.
449 This is generally done via an C<auto> action/method (prior to Catalyst
450 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
451 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
453 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
454 the following method:
458 Check if there is a user and, if not, forward to login page
462 # Note that 'auto' runs after 'begin' but before your actions and that
463 # 'auto's "chain" (all from application path to most specific class are run)
464 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
468 # Allow unauthenticated users to reach the login page. This
469 # allows unauthenticated users to reach any action in the Login
470 # controller. To lock it down to a single action, we could use:
471 # if ($c->action eq $c->controller('Login')->action_for('index'))
472 # to only allow unauthenticated access to the 'index' action we
474 if ($c->controller eq $c->controller('Login')) {
478 # If a user doesn't exist, force login
479 if (!$c->user_exists) {
480 # Dump a log message to the development server debug output
481 $c->log->debug('***Root::auto User not found, forwarding to /login');
482 # Redirect the user to the login page
483 $c->response->redirect($c->uri_for('/login'));
484 # Return 0 to cancel 'post-auto' processing and prevent use of application
488 # User found, so return 1 to continue with processing after this 'auto'
493 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
494 every C<auto> method from the application/root controller down to the
495 most specific controller will be called. By placing the
496 authentication enforcement code inside the C<auto> method of
497 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
498 called for I<every> request that is received by the entire
502 =head2 Displaying Content Only to Authenticated Users
504 Let's say you want to provide some information on the login page that
505 changes depending on whether the user has authenticated yet. To do
506 this, open C<root/src/login.tt2> in your editor and add the following
507 lines to the bottom of the file:
512 # This code illustrates how certain parts of the TT
513 # template will only be shown to users who have logged in
515 [% IF c.user_exists %]
516 Please Note: You are already logged in as '[% c.user.username %]'.
517 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
519 You need to log in to use this application.
522 Note that this whole block is a comment because the "#" appears
523 immediate after the "[%" (with no spaces in between). Although it
524 can be a handy way to temporarily "comment out" a whole block of
525 TT code, it's probably a little too subtle for use in "normal"
530 Although most of the code is comments, the middle few lines provide a
531 "you are already logged in" reminder if the user returns to the login
532 page after they have already authenticated. For users who have not yet
533 authenticated, a "You need to log in..." message is displayed (note the
534 use of an IF-THEN-ELSE construct in TT).
537 =head2 Try Out Authentication
539 Press C<Ctrl-C> to kill the previous server instance (if it's still
540 running) and restart it:
542 $ script/myapp_server.pl
544 B<IMPORTANT NOTE:> If you are having issues with authentication on
545 Internet Explorer, be sure to check the system clocks on both your
546 server and client machines. Internet Explorer is very picky about
547 timestamps for cookies. You can quickly sync a Debian system by
548 installing the "ntpdate" package:
550 sudo aptitude -y install ntpdate
552 And then run the following command:
556 Or, depending on your firewall configuration:
558 sudo ntpdate-debian -u
560 Note: NTP can be a little more finicky about firewalls because it uses
561 UDP vs. the more common TCP that you see with most Internet protocols.
562 Worse case, you might have to manually set the time on your development
563 box instead of using NTP.
565 Now trying going to L<http://localhost:3000/books/list> and you should
566 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
567 if necessary (the "You are already logged in" message should I<not>
568 appear -- if it does, click the C<logout> button and try again). Note
569 the C<***Root::auto User not found...> debug message in the
570 development server output. Enter username C<test01> and password
571 C<mypass>, and you should be taken to the Book List page.
573 Open C<root/src/books/list.tt2> and add the following lines to the
574 bottom (below the closing </table> tag):
577 <a href="[% c.uri_for('/login') %]">Login</a>
578 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
581 Reload your browser and you should now see a "Login" and "Create" links
582 at the bottom of the page (as mentioned earlier, you can update template
583 files without reloading the development server). Click the first link
584 to return to the login page. This time you I<should> see the "You are
585 already logged in" message.
587 Finally, click the C<You can logout here> link on the C</login> page.
588 You should stay at the login page, but the message should change to "You
589 need to log in to use this application."
592 =head1 USING PASSWORD HASHES
594 In this section we increase the security of our system by converting
595 from cleartext passwords to SHA-1 password hashes that include a
596 random "salt" value to make them extremely difficult to crack with
597 dictionary and "rainbow table" attacks.
599 B<Note:> This section is optional. You can skip it and the rest of the
600 tutorial will function normally.
602 Be aware that even with the techniques shown in this section, the browser
603 still transmits the passwords in cleartext to your application. We are
604 just avoiding the I<storage> of cleartext passwords in the database by
605 using a salted SHA-1 hash. If you are concerned about cleartext passwords
606 between the browser and your application, consider using SSL/TLS, made
607 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
610 =head2 Install DBIx::Class::EncodedColumn
612 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> provides features
613 that can greatly simplify the maintenance of passwords. It's currently
614 not available as a .deb package in the normal Debian repositories, so let's
615 install it directly from CPAN:
617 $ sudo cpan DBIx::Class::EncodedColumn
620 =head2 Re-Run the DBIC::Schema Model Helper to Include DBIx::Class::EncodedColumn
622 Next, we can re-run the model helper to have it include
623 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> in all of the
624 Result Classes it generates for us. Simply use the same command we
625 saw in Chapters 3 and 4, but add C<,EncodedColumn> to the C<components>
628 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
629 create=static components=TimeStamp,EncodedColumn dbi:SQLite:myapp.db
631 If you then open one of the Result Classes, you will see that it
632 includes EncodedColumn in the C<load_components> line. Take a look at
633 C<lib/MyApp/Schema/Result/Users.pm> since that's the main class where we
634 want to use hashed and salted passwords:
636 __PACKAGE__->load_components("InflateColumn::DateTime", "TimeStamp", "EncodedColumn", "Core");
639 =head2 Modify the "password" Column to Use EncodedColumn
641 Open the file C<lib/MyApp/Schema/Result/Users.pm> and enter the following
642 text below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" line but above
645 # Have the 'password' column use a SHA-1 hash and 10-character salt
646 # with hex encoding; Generate the 'check_password" method
647 __PACKAGE__->add_columns(
652 encode_class => 'Digest',
653 encode_args => {salt_length => 10},
654 encode_check_method => 'check_password',
658 This redefines the automatically generated definition for the password
659 fields at the top of the Result Class file to now use EncodedColumn
660 logic (C<encoded_column> is set to 1). C<encode_class> can be set to
661 either C<Digest> to use
662 L<DBIx::Class::EncodedColumn::Digest|DBIx::Class::EncodedColumn::Digest>,
663 or C<Crypt::Eksblowfish::Bcrypt> for
664 L<DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt|DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt>.
665 C<encode_args> is then used to customize the type of Digest you
666 selected. Here we only specified the size of the salt to use, but
667 we could have also modified the hashing algorithm ('SHA-256' is
668 the default) and the format to use ('base64' is the default, but
669 'hex' and 'binary' are other options). To use these, you could
670 change the C<encode_args> to something like:
672 encode_args => {algorithm => 'SHA-1',
677 =head2 Load Hashed Passwords in the Database
679 Next, let's create a quick script to load some hashed and salted passwords
680 into the C<password> column of our C<users> table. Open the file
681 C<set_hashed_passwords.pl> in your editor and enter the following text:
690 my $schema = MyApp::Schema->connect('dbi:SQLite:myapp.db');
692 my @users = $schema->resultset('Users')->all;
694 foreach my $user (@users) {
695 $user->password('mypass');
699 EncodedColumn lets us simple call C<$user->check_password($password)>
700 to see if the user has supplied the correct password, or, as we show
701 above, call C<$user->update($new_password)> to update the hashed
702 password stored for this user.
704 Then run the following command:
706 $ perl -Ilib set_hashed_passwords.pl
708 We had to use the C<-Ilib> arguement to tell perl to look under the
709 C<lib> directory for our C<MyApp::Schema> model.
711 Then dump the users table to verify that it worked:
713 $ sqlite3 myapp.db "select * from users"
714 1|test01|38d3974fa9e9263099f7bc2574284b2f55473a9bM=fwpX2NR8|t01@na.com|Joe|Blow|1
715 2|test02|6ed8586587e53e0d7509b1cfed5df08feadc68cbMJlnPyPt0I|t02@na.com|Jane|Doe|1
716 3|test03|af929a151340c6aed4d54d7e2651795d1ad2e2f7UW8dHoGv9z|t03@na.com|No|Go|0
718 As you can see, the passwords are much harder to steal from the
719 database. Also note that this demonstrates how to use a DBIx::Class
720 model outside of your web application -- a very useful feature in many
724 =head2 Enable Hashed and Salted Passwords
726 Edit C<lib/MyApp.pm> and update it to match the following text (the only change
727 is to the C<password_type> field):
729 # Configure SimpleDB Authentication
730 __PACKAGE__->config->{'Plugin::Authentication'} = {
733 user_model => 'DB::Users',
734 password_type => 'self_check',
738 The use of C<self_check> will cause
739 Catalyst::Plugin::Authentication::Store::DBIC to call the
740 C<check_password> method we enabled on our C<password> columns.
743 =head2 Try Out the Hashed Passwords
745 Press C<Ctrl-C> to kill the previous server instance (if it's still
746 running) and restart it:
748 $ script/myapp_server.pl
750 You should now be able to go to L<http://localhost:3000/books/list> and
751 login as before. When done, click the "logout" link on the login page
752 (or point your browser at L<http://localhost:3000/logout>).
755 =head1 USING THE SESSION FOR FLASH
757 As discussed in the previous chapter of the tutorial, C<flash> allows
758 you to set variables in a way that is very similar to C<stash>, but it
759 will remain set across multiple requests. Once the value is read, it
760 is cleared (unless reset). Although C<flash> has nothing to do with
761 authentication, it does leverage the same session plugins. Now that
762 those plugins are enabled, let's go back and update the "delete and
763 redirect with query parameters" code seen at the end of the L<Basic
764 CRUD|Catalyst::Manual::Tutorial::BasicCRUD> chapter of the tutorial to
765 take advantage of C<flash>.
767 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
768 to match the following (everything after the model search line of code
777 sub delete :Chained('object') :PathPart('delete') :Args(0) {
780 # Use the book object saved by 'object' and delete it along
781 # with related 'book_authors' entries
782 $c->stash->{object}->delete;
784 # Use 'flash' to save information across requests until it's read
785 $c->flash->{status_msg} = "Book deleted";
787 # Redirect the user back to the list page
788 $c->response->redirect($c->uri_for($self->action_for('list')));
791 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
792 flash vs. the C<status_msg> query parameter:
796 [%# Status and error messages %]
797 <span class="message">[% status_msg || c.flash.status_msg %]</span>
798 <span class="error">[% error_msg %]</span>
799 [%# This is where TT will stick all of your template's contents. -%]
801 </div><!-- end content -->
804 Although the sample above only shows the C<content> div, leave the
805 rest of the file intact -- the only change we made to the C<wrapper.tt2>
806 was to add "C<|| c.request.params.status_msg>" to the
807 C<E<lt>span class="message"E<gt>> line.
812 Restart the development server, log in, and then point your browser to
813 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
814 several books. Click the "Return to list" link and delete one of the
815 "Test" books you just added. The C<flash> mechanism should retain our
816 "Book deleted" status message across the redirect.
818 B<NOTE:> While C<flash> will save information across multiple requests,
819 I<it does get cleared the first time it is read>. In general, this is
820 exactly what you want -- the C<flash> message will get displayed on
821 the next screen where it's appropriate, but it won't "keep showing up"
822 after that first time (unless you reset it). Please refer to
823 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
827 =head2 Switch To Flash-To-Stash
829 Although the a use of flash above works well, the
830 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
831 alternative is to use the C<flash_to_stash> feature that automatically
832 copies the content of flash to stash. This makes your controller
833 and template code work regardless of where it was directly access, a
834 forward, or a redirect. To enable C<flash_to_stash>, you can either
835 set the value in C<lib/MyApp.pm> by changing the default
836 C<__PACKAGE__-E<gt>config> setting to something like:
840 session => {flash_to_stash => 1}
843 B<or> add the following to C<myapp.conf>:
849 The C<__PACKAGE__-E<gt>config> option is probably preferable here
850 since it's not something you will want to change at runtime without it
851 possibly breaking some of your code.
853 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
854 to match the following:
856 <span class="message">[% status_msg %]</span>
858 Restart the development server and go to
859 L<http://localhost:3000/books/list> in your browser. Delete another
860 of the "Test" books you added in the previous step. Flash should still
861 maintain the status message across the redirect even though you are no
862 longer explicitly accessing C<c.flash>.
867 Kennedy Clark, C<hkclark@gmail.com>
869 Please report any errors, issues or suggestions to the author. The
870 most recent version of the Catalyst Tutorial can be found at
871 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
873 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
874 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).