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('/books/list'));
398 # Set an error message
399 $c->stash->{error_msg} = "Bad username or password.";
403 # If either of above don't work out, send to the login page
404 $c->stash->{template} = 'login.tt2';
407 This controller fetches the C<username> and C<password> values from the
408 login form and attempts to authenticate the user. If successful, it
409 redirects the user to the book list page. If the login fails, the user
410 will stay at the login page and receive an error message. If the
411 C<username> and C<password> values are not present in the form, the
412 user will be taken to the empty login form.
414 Note that we could have used something like C<sub default :Path>,
415 however, it is generally recommended (partly for historical reasons,
416 and partly for code clarity) only to use C<default> in
417 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
418 found page for the application.
420 Instead, we are using C<sub base :Path :Args(0) {...}> here to
421 specifically match the URL C</login>. C<Path> actions (aka, "literal
422 actions") create URI matches relative to the namespace of the
423 controller where they are defined. Although C<Path> supports
424 arguments that allow relative and absolute paths to be defined, here
425 we use an empty C<Path> definition to match on just the name of the
426 controller itself. The method name, C<index>, is arbitrary. We make
427 the match even more specific with the C<:Args(0)> action modifier --
428 this forces the match on I<only> C</login>, not
429 C</login/somethingelse>.
431 Next, update the corresponding method in
432 C<lib/MyApp/Controller/Logout.pm> to match:
440 sub index :Path :Args(0) {
443 # Clear the user's state
446 # Send the user to the starting point
447 $c->response->redirect($c->uri_for('/'));
450 As with the login controller, be sure to delete the
451 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
452 line of the C<sub index>.
455 =head2 Add a Login Form TT Template Page
457 Create a login form by opening C<root/src/login.tt2> and inserting:
459 [% META title = 'Login' %]
462 <form method="post" action="[% c.uri_for('/login') %]">
466 <td><input type="text" name="username" size="40" /></td>
470 <td><input type="password" name="password" size="40" /></td>
473 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
479 =head2 Add Valid User Check
481 We need something that provides enforcement for the authentication
482 mechanism -- a I<global> mechanism that prevents users who have not
483 passed authentication from reaching any pages except the login page.
484 This is generally done via an C<auto> action/method (prior to Catalyst
485 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
486 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
488 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
489 the following method:
493 Check if there is a user and, if not, forward to login page
497 # Note that 'auto' runs after 'begin' but before your actions and that
498 # 'auto's "chain" (all from application path to most specific class are run)
499 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
503 # Allow unauthenticated users to reach the login page. This
504 # allows unauthenticated users to reach any action in the Login
505 # controller. To lock it down to a single action, we could use:
506 # if ($c->action eq $c->controller('Login')->action_for('index'))
507 # to only allow unauthenticated access to the 'index' action we
509 if ($c->controller eq $c->controller('Login')) {
513 # If a user doesn't exist, force login
514 if (!$c->user_exists) {
515 # Dump a log message to the development server debug output
516 $c->log->debug('***Root::auto User not found, forwarding to /login');
517 # Redirect the user to the login page
518 $c->response->redirect($c->uri_for('/login'));
519 # Return 0 to cancel 'post-auto' processing and prevent use of application
523 # User found, so return 1 to continue with processing after this 'auto'
528 B<Note:> Catalyst provides a number of different types of actions,
529 such as C<Local>, C<Regex>, C<Private> and the new C<Path>. You
530 should refer to L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> for
531 a more detailed explanation, but the following bullet points provide a
538 The majority of applications have traditionally used C<Local> actions
539 for items that respond to user requests and C<Private> actions for
540 those that do not directly respond to user input.
544 Newer Catalyst applications tend to use C<Path> actions and the
545 C<Args> attribute because of their power and flexibility. You can
546 specify the path to match relative to the namespace of the current
547 module as an argument to C<Path>. For example C<Path('list')> in
548 C<lib/MyApp/Controller/Books.pm> would match on the URL
549 C<http://localhost:3000/books/list> but C<Path('/list')> would
550 match on C<http://localhost:3000/list>.
554 Automatic "chaining" of actions by the dispatcher is a powerful
555 feature that allows multiple methods to handle a single URL. See
556 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
557 for more information on chained actions.
561 There are five types of build-in C<Private> actions: C<begin>, C<end>,
562 C<default>, C<index>, and C<auto>.
566 With C<begin>, C<end>, C<default>, C<index> private actions, only the
567 most specific action of each type will be called. For example, if you
568 define a C<begin> action in your controller it will I<override> a
569 C<begin> action in your application/root controller -- I<only> the
570 action in your controller will be called.
574 Unlike the other actions where only a single method is called for each
575 request, I<every> auto action along the chain of namespaces will be
576 called. Each C<auto> action will be called I<from the application/root
577 controller down through the most specific class>.
581 By placing the authentication enforcement code inside the C<auto> method
582 of C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
583 called for I<every> request that is received by the entire application.
586 =head2 Displaying Content Only to Authenticated Users
588 Let's say you want to provide some information on the login page that
589 changes depending on whether the user has authenticated yet. To do
590 this, open C<root/src/login.tt2> in your editor and add the following
591 lines to the bottom of the file:
595 # This code illustrates how certain parts of the TT
596 # template will only be shown to users who have logged in
598 [% IF c.user_exists %]
599 Please Note: You are already logged in as '[% c.user.username %]'.
600 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
602 You need to log in to use this application.
605 Note that this whole block is a comment because the "#" appears
606 immediate after the "[%" (with no spaces in between). Although it
607 can be a handy way to temporarily "comment out" a whole block of
608 TT code, it's probably a little too subtle for use in "normal"
613 Although most of the code is comments, the middle few lines provide a
614 "you are already logged in" reminder if the user returns to the login
615 page after they have already authenticated. For users who have not yet
616 authenticated, a "You need to log in..." message is displayed (note the
617 use of an IF-THEN-ELSE construct in TT).
620 =head2 Try Out Authentication
622 Press C<Ctrl-C> to kill the previous server instance (if it's still
623 running) and restart it:
625 $ script/myapp_server.pl
627 B<IMPORTANT NOTE:> If you are having issues with authentication on
628 Internet Explorer, be sure to check the system clocks on both your
629 server and client machines. Internet Explorer is very picky about
630 timestamps for cookies. Note that you can quickly sync an Ubuntu
631 system with the following command:
633 sudo ntpdate ntp.ubuntu.com
635 Or possibly try C<sudo ntpdate -u ntp.ubuntu.com> (to us an
636 unpriviledged port) or C<sudo ntpdate pool.ntp.org> (to try a
637 different server in case the Ubuntu NTP server is down).
639 Now trying going to L<http://localhost:3000/books/list> and you should
640 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
641 if necessary (the "You are already logged in" message should I<not>
642 appear -- if it does, click the C<logout> button and try again). Note
643 the C<***Root::auto User not found...> debug message in the
644 development server output. Enter username C<test01> and password
645 C<mypass>, and you should be taken to the Book List page.
647 Open C<root/src/books/list.tt2> and add the following lines to the
648 bottom (below the closing </table> tag):
651 <a href="[% c.uri_for('/login') %]">Login</a>
652 <a href="[% c.uri_for('form_create') %]">Create</a>
655 Reload your browser and you should now see a "Login" and "Create" links
656 at the bottom of the page (as mentioned earlier, you can update template
657 files without reloading the development server). Click the first link
658 to return to the login page. This time you I<should> see the "You are
659 already logged in" message.
661 Finally, click the C<You can logout here> link on the C</login> page.
662 You should stay at the login page, but the message should change to "You
663 need to log in to use this application."
666 =head1 USING PASSWORD HASHES
668 In this section we increase the security of our system by converting
669 from cleartext passwords to SHA-1 password hashes.
671 B<Note:> This section is optional. You can skip it and the rest of the
672 tutorial will function normally.
674 Note that even with the techniques shown in this section, the browser
675 still transmits the passwords in cleartext to your application. We are
676 just avoiding the I<storage> of cleartext passwords in the database by
677 using a SHA-1 hash. If you are concerned about cleartext passwords
678 between the browser and your application, consider using SSL/TLS, made
679 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
682 =head2 Get a SHA-1 Hash for the Password
684 Catalyst uses the C<Digest> module to support a variety of hashing
685 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
686 First, we should compute the SHA-1 hash for the "mypass" password we are
687 using. The following command-line Perl script provides a "quick and
688 dirty" way to do this:
690 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
691 e727d1464ae12436e899a726da5b2f11d8381b26
694 B<Note:> If you are following along in Ubuntu, you will need to install
695 C<Digest::SHA> with the following command to run the example code above:
697 sudo aptitude install libdigest-sha-perl
699 B<Note:> You should probably modify this code for production use to
700 not read the password from the command line. By having the script
701 prompt for the cleartext password, it avoids having the password linger
702 in forms such as your C<.bash_history> files (assuming you are using
703 BASH as your shell). An example of such a script can be found in
707 =head2 Switch to SHA-1 Password Hashes in the Database
709 Next, we need to change the C<password> column of our C<users> table to
710 store this hash value vs. the existing cleartext password. Open
711 C<myapp03.sql> in your editor and enter:
714 -- Convert passwords to SHA-1 hashes
716 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
717 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
718 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
720 Then use the following command to update the SQLite database:
722 $ sqlite3 myapp.db < myapp03.sql
724 B<Note:> We are using SHA-1 hashes here, but many other hashing
725 algorithms are supported. See C<Digest> for more information.
728 =head2 Enable SHA-1 Hash Passwords in
729 C<Catalyst::Plugin::Authentication::Store::DBIC>
731 Edit C<myapp.conf> and update it to match (the C<password_type> and
732 C<password_hash_type> are new, everything else is the same):
734 # rename this file to MyApp.yml and put a : in front of "name" if
735 # you want to use yaml like in old versions of Catalyst
742 # Note this first definition would be the same as setting
743 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
744 # ->{credential} = 'Password' in lib/MyApp.pm
746 # Specify that we are going to do password-based auth
748 # This is the name of the field in the users table with the
749 # password stored in it
750 password_field password
751 # Switch to more secure hashed passwords
753 # Use the SHA-1 hashing algorithm
754 password_hash_type SHA-1
757 # Use DBIC to retrieve username, password & role information
759 # This is the model object created by Catalyst::Model::DBIC
760 # from your schema (you created 'MyApp::Schema::User' but as
761 # the Catalyst startup debug messages show, it was loaded as
762 # 'MyApp::Model::DB::Users').
763 # NOTE: Omit 'MyApp::Model' here just as you would when using
764 # '$c->model("DB::Users)'
772 =head2 Try Out the Hashed Passwords
774 Press C<Ctrl-C> to kill the previous server instance (if it's still
775 running) and restart it:
777 $ script/myapp_server.pl
779 You should now be able to go to L<http://localhost:3000/books/list> and
780 login as before. When done, click the "Logout" link on the login page
781 (or point your browser at L<http://localhost:3000/logout>).
784 =head1 USING THE SESSION FOR FLASH
786 As discussed in Part 3 of the tutorial, C<flash> allows you to set
787 variables in a way that is very similar to C<stash>, but it will
788 remain set across multiple requests. Once the value is read, it
789 is cleared (unless reset). Although C<flash> has nothing to do with
790 authentication, it does leverage the same session plugins. Now that
791 those plugins are enabled, let's go back and improve the "delete
792 and redirect with query parameters" code seen at the end of the
793 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
796 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
797 to match the following (everything after the model search line of code
807 # $id = primary key of book to delete
808 my ($self, $c, $id) = @_;
810 # Search for the book and then delete it
811 $c->model('DB::Books')->search({id => $id})->delete_all;
813 # Use 'flash' to save information across requests until it's read
814 $c->flash->{status_msg} = "Book deleted";
816 # Redirect the user back to the list page
817 $c->response->redirect($c->uri_for('/books/list'));
820 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
821 flash vs. the C<status_msg> query parameter:
825 [%# Status and error messages %]
826 <span class="message">[% status_msg || c.flash.status_msg %]</span>
827 <span class="error">[% error_msg %]</span>
828 [%# This is where TT will stick all of your template's contents. -%]
830 </div><!-- end content -->
833 Although the sample above only shows the C<content> div, leave the
834 rest of the file intact -- the only change we made to the C<wrapper.tt2>
835 was to add "C<|| c.request.params.status_msg>" to the
836 C<E<lt>span class="message"E<gt>> line.
841 Restart the development server and point your browser to
842 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
843 several books. Click the "Return to list" link and delete one of the
844 "Test" books you just added. The C<flash> mechanism should retain our
845 "Book deleted" status message across the redirect.
847 B<NOTE:> While C<flash> will save information across multiple requests,
848 I<it does get cleared the first time it is read>. In general, this is
849 exactly what you want -- the C<flash> message will get displayed on
850 the next screen where it's appropriate, but it won't "keep showing up"
851 after that first time (unless you reset it). Please refer to
852 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
856 =head2 Switch To Flash-To-Stash
858 Although the a use of flash above is certainly an improvement over the
859 C<status_msg> we employed in Part 4 of the tutorial, the
860 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
861 alternative is to use the C<flash_to_stash> feature that automatically
862 copies the content of flash to stash. This makes your controller
863 and template code work regardless of where it was directly access, a
864 forward, or a redirect. To enable C<flash_to_stash>, you can either
865 set the value in C<lib/MyApp.pm> by changing the default
866 C<__PACKAGE__-E<gt>config> setting to something like:
870 session => {flash_to_stash => 1}
873 B<or> add the following to C<myapp.conf>:
879 The C<__PACKAGE__-E<gt>config> option is probably preferable here
880 since it's not something you will want to change at runtime without it
881 possibly breaking some of your code.
883 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
884 to match the following:
886 <span class="message">[% status_msg %]</span>
888 Restart the development server and go to
889 L<http://localhost:3000/books/list> in your browser. Delete another
890 of the "Test" books you added in the previous step. Flash should still
891 maintain the status message across the redirect even though you are no
892 longer explicitly accessing C<c.flash>.
897 Kennedy Clark, C<hkclark@gmail.com>
899 Please report any errors, issues or suggestions to the author. The
900 most recent version of the Catalyst Tutorial can be found at
901 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
903 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
904 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).