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>
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 $ ls lib/MyApp/Schema
130 Authors.pm BookAuthors.pm Books.pm Roles.pm UserRoles.pm Users.pm
132 Notice how the helper has added three new table-specific result source
133 files to the C<lib/MyApp/Schema/MyApp> directory. And, more
134 importantly, even if there were changes to the existing result source
135 files, those changes would have only been written above the C<# DO NOT
136 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-editted
137 enhancements would have been preserved.
140 Speaking of "hand-editted enhancements," we should now add
141 relationship information to the three new result source files. Edit
142 each of these files and add the following information between the C<#
143 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
145 C<lib/MyApp/Schema/Users.pm>:
153 # 1) Name of relationship, DBIC will create accessor with this name
154 # 2) Name of the model class referenced by this relationship
155 # 3) Column name in *foreign* table
156 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'user_id');
160 # 1) Name of relationship, DBIC will create accessor with this name
161 # 2) Name of has_many() relationship this many_to_many() is shortcut for
162 # 3) Name of belongs_to() relationship in model class of has_many() above
163 # You must already have the has_many() defined to use a many_to_many().
164 __PACKAGE__->many_to_many(roles => 'map_user_role', 'role');
167 C<lib/MyApp/Schema/Roles.pm>:
175 # 1) Name of relationship, DBIC will create accessor with this name
176 # 2) Name of the model class referenced by this relationship
177 # 3) Column name in *foreign* table
178 __PACKAGE__->has_many(map_user_role => 'MyApp::Schema::UserRoles', 'role_id');
181 C<lib/MyApp/Schema/UserRoles.pm>:
189 # 1) Name of relationship, DBIC will create accessor with this name
190 # 2) Name of the model class referenced by this relationship
191 # 3) Column name in *this* table
192 __PACKAGE__->belongs_to(user => 'MyApp::Schema::Users', 'user_id');
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(role => 'MyApp::Schema::Roles', 'role_id');
202 The code for these three sets of updates is obviously very similar to
203 the edits we made to the C<Books>, C<Authors>, and C<BookAuthors>
204 classes created in Part 3.
206 Note that we do not need to make any change to the
207 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to
208 load all of the result class files it finds in below the
209 C<lib/MyApp/Schema> directory, so it will automatically pick
210 up our new table information.
213 =head2 Sanity-Check Reload of Development Server
215 We aren't ready to try out the authentication just yet; we only want
216 to do a quick check to be sure our model loads correctly. Press
217 C<Ctrl-C> to kill the previous server instance (if it's still running)
220 $ script/myapp_server.pl
222 Look for the three new model objects in the startup debug output:
225 .-------------------------------------------------------------------+----------.
227 +-------------------------------------------------------------------+----------+
228 | MyApp::Controller::Books | instance |
229 | MyApp::Controller::Root | instance |
230 | MyApp::Model::DB | instance |
231 | MyApp::Model::DB::Author | class |
232 | MyApp::Model::DB::Books | class |
233 | MyApp::Model::DB::BookAuthors | class |
234 | MyApp::Model::DB::Roles | class |
235 | MyApp::Model::DB::Users | class |
236 | MyApp::Model::DB::UserRoles | class |
237 | MyApp::View::TT | instance |
238 '-------------------------------------------------------------------+----------'
241 Again, notice that your "result class" classes have been "re-loaded"
242 by Catalyst under C<MyApp::Model>.
245 =head2 Include Authentication and Session Plugins
247 Edit C<lib/MyApp.pm> and update it as follows (everything below
248 C<StackTrace> is new):
260 Session::Store::FastMmap
261 Session::State::Cookie
264 The C<Authentication> plugin supports Authentication while the
265 C<Session> plugins are required to maintain state across multiple HTTP
268 Note that the only required Authentication class is the main one. This
269 is a change that occurred in version 0.09999_01 of the
270 C<Authentication> plugin. You B<do not need> to specify a particular
271 Authentication::Store or Authentication::Credential plugin. Instead,
272 indicate the Store and Credential you want to use in your application
273 configuration (see below).
275 Note that there are several options for
276 L<Session::Store|Catalyst::Plugin::Session::Store>
277 (L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap>
278 is generally a good choice if you are on Unix; try
279 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
280 are on Win32) -- consult
281 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
282 for additional information and options (for example to use a database-
283 backed session store).
286 =head2 Configure Authentication
288 Although C<__PACKAGE__-E<gt>config(name =E<gt> 'value');> is still
289 supported, newer Catalyst applications tend to place all configuration
290 information in C<myapp.conf> and automatically load this information
291 into C<MyApp-E<gt>config> using the
292 L<ConfigLoader|Catalyst::Plugin::ConfigLoader> plugin.
294 First, as noted in Part 3 of the tutorial, Catalyst has recently
295 switched from a default config file format of YAML to
296 C<Config::General> (an apache-like format). In case you are using a
297 version of Catalyst earlier than v5.7014, delete the C<myapp.yml>, or
298 convert it to .conf format using the TIP in
299 L<Catalyst::Manual::MoreCatalystBasics>; then simply follow the
300 directions below to create a new C<myapp.conf> file.
302 Here, we need to load several parameters that tell
303 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
304 where to locate information in your database. To do this, edit the
305 C<myapp.conf> file and update it to match:
313 # Note: this first definition would be the same as setting
314 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
315 # ->{credential} = 'Password' in lib/MyApp.pm
317 # Specify that we are going to do password-based auth
319 # This is the name of the field in the users table with the
320 # password stored in it
321 password_field password
322 # We are using an unencrypted password for now
326 # Use DBIC to retrieve username, password & role information
328 # This is the model object created by Catalyst::Model::DBIC
329 # from your schema (you created 'MyApp::Schema::User' but as
330 # the Catalyst startup debug messages show, it was loaded as
331 # 'MyApp::Model::DB::Users').
332 # NOTE: Omit 'MyApp::Model' here just as you would when using
333 # '$c->model("DB::Users)'
335 # This is the name of the field in your 'users' table that
336 # contains the user's name
343 Inline comments in the code above explain how each field is being used.
345 Note that you can use many other config file formats with catalyst.
346 See L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
349 =head2 Add Login and Logout Controllers
351 Use the Catalyst create script to create two stub controller files:
353 $ script/myapp_create.pl controller Login
354 $ script/myapp_create.pl controller Logout
356 B<NOTE:> You could easily use a single controller here. For example,
357 you could have a C<User> controller with both C<login> and C<logout>
358 actions. Remember, Catalyst is designed to be very flexible, and leaves
359 such matters up to you, the designer and programmer.
361 Then open C<lib/MyApp/Controller/Login.pm>, locate the C<sub index
362 :Path :Args(0)> method (or C<sub index : Private> if you are using an
363 older version of Catalyst) that was automatically inserted by the
364 helpers when we created the Login controller above, and delete this
367 $c->response->body('Matched MyApp::Controller::Login in Login.');
369 Then update it to match:
377 sub index :Path :Args(0) {
380 # Get the username and password from form
381 my $username = $c->request->params->{username} || "";
382 my $password = $c->request->params->{password} || "";
384 # If the username and password values were found in form
385 if ($username && $password) {
386 # Attempt to log the user in
387 if ($c->authenticate({ username => $username,
388 password => $password} )) {
389 # If successful, then let them use the application
390 $c->response->redirect($c->uri_for('/books/list'));
393 # Set an error message
394 $c->stash->{error_msg} = "Bad username or password.";
398 # If either of above don't work out, send to the login page
399 $c->stash->{template} = 'login.tt2';
402 This controller fetches the C<username> and C<password> values from the
403 login form and attempts to authenticate the user. If successful, it
404 redirects the user to the book list page. If the login fails, the user
405 will stay at the login page and receive an error message. If the
406 C<username> and C<password> values are not present in the form, the
407 user will be taken to the empty login form.
409 Note that we could have used something like C<sub default :Path>,
410 however partly for historical reasons, and partly for code clarity it
411 is generally recommended only to use C<default> in
412 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
413 found page for the application.
415 Instead, we are using C<sub base :Path :Args(0) {...}> here to
416 specifically match the URL C</login>. C<Path> actions (aka, "literal
417 actions") create URI matches relative to the namespace of the
418 controller where they are defined. Although C<Path> supports
419 arguments that allow relative and absolute paths to be defined, here
420 we use an empty C<Path> definition to match on just the name of the
421 controller itself. The method name, C<index>, is arbitrary. We make
422 the match even more specific with the C<:Args(0)> action modifier --
423 this forces the match on I<only> C</login>, not
424 C</login/somethingelse>.
426 Next, update the corresponding method in
427 C<lib/MyApp/Controller/Logout.pm> to match:
435 sub index :Path :Args(0) {
438 # Clear the user's state
441 # Send the user to the starting point
442 $c->response->redirect($c->uri_for('/'));
445 As with the login controller, be sure to delete the
446 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
447 line of the C<sub index>.
450 =head2 Add a Login Form TT Template Page
452 Create a login form by opening C<root/src/login.tt2> and inserting:
454 [% META title = 'Login' %]
457 <form method="post" action="[% c.uri_for('/login') %]">
461 <td><input type="text" name="username" size="40" /></td>
465 <td><input type="password" name="password" size="40" /></td>
468 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
474 =head2 Add Valid User Check
476 We need something that provides enforcement for the authentication
477 mechanism -- a I<global> mechanism that prevents users who have not
478 passed authentication from reaching any pages except the login page.
479 This is generally done via an C<auto> action/method (prior to Catalyst
480 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
481 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
483 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
484 the following method:
488 Check if there is a user and, if not, forward to login page
492 # Note that 'auto' runs after 'begin' but before your actions and that
493 # 'auto's "chain" (all from application path to most specific class are run)
494 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
498 # Allow unauthenticated users to reach the login page. This
499 # allows anauthenticated users to reach any action in the Login
500 # controller. To lock it down to a single action, we could use:
501 # if ($c->action eq $c->controller('Login')->action_for('index'))
502 # to only allow unauthenticated access to the 'index' action we
504 if ($c->controller eq $c->controller('Login')) {
508 # If a user doesn't exist, force login
509 if (!$c->user_exists) {
510 # Dump a log message to the development server debug output
511 $c->log->debug('***Root::auto User not found, forwarding to /login');
512 # Redirect the user to the login page
513 $c->response->redirect($c->uri_for('/login'));
514 # Return 0 to cancel 'post-auto' processing and prevent use of application
518 # User found, so return 1 to continue with processing after this 'auto'
523 B<Note:> Catalyst provides a number of different types of actions,
524 such as C<Local>, C<Regex>, C<Private> and the new C<Path>. You
525 should refer to L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> for
526 a more detailed explanation, but the following bullet points provide a
533 The majority of application have traditionally used C<Local> actions
534 for items that respond to user requests and C<Private> actions for
535 those that do not directly respond to user input.
539 Newer Catalyst applications tend to use C<Path> actions and the
540 C<Args> attribute because of their power and flexibility. You can
541 specify the path to match relative to the namespace of the current
542 module as an argument to C<Path>. For example C<Path('list')> in
543 C<lib/MyApp/Controller/Books.pm> would match on the URL
544 C<http://localhost:3000/books/list> but C<Path('/list')> would
545 match on C<http://localhost:3000/list>.
549 Automatic "chaining" of actions by the dispatcher is a powerful
550 feature that allows multiple methods to handle a single URL. See
551 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
552 for more information on chained actions.
556 There are five types of build-in C<Private> actions: C<begin>, C<end>,
557 C<default>, C<index>, and C<auto>.
561 With C<begin>, C<end>, C<default>, C<index> private actions, only the
562 most specific action of each type will be called. For example, if you
563 define a C<begin> action in your controller it will I<override> a
564 C<begin> action in your application/root controller -- I<only> the
565 action in your controller will be called.
569 Unlike the other actions where only a single method is called for each
570 request, I<every> auto action along the chain of namespaces will be
571 called. Each C<auto> action will be called I<from the application/root
572 controller down through the most specific class>.
576 By placing the authentication enforcement code inside the C<auto> method
577 of C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
578 called for I<every> request that is received by the entire application.
581 =head2 Displaying Content Only to Authenticated Users
583 Let's say you want to provide some information on the login page that
584 changes depending on whether the user has authenticated yet. To do
585 this, open C<root/src/login.tt2> in your editor and add the following
586 lines to the bottom of the file:
590 # This code illustrates how certain parts of the TT
591 # template will only be shown to users who have logged in
593 [% IF c.user_exists %]
594 Please Note: You are already logged in as '[% c.user.username %]'.
595 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
597 You need to log in to use this application.
600 Note that this whole block is a comment because the "#" appears
601 immediate after the "[%" (with no spaces in between). Although it
602 can be a handy way to temporarily "comment out" a whole block of
603 TT code, it's probably a little too subtle for use in "normal"
608 Although most of the code is comments, the middle few lines provide a
609 "you are already logged in" reminder if the user returns to the login
610 page after they have already authenticated. For users who have not yet
611 authenticated, a "You need to log in..." message is displayed (note the
612 use of an IF-THEN-ELSE construct in TT).
615 =head2 Try Out Authentication
617 Press C<Ctrl-C> to kill the previous server instance (if it's still
618 running) and restart it:
620 $ script/myapp_server.pl
622 B<IMPORTANT NOTE:> If you are having issues with authentication on
623 Internet Explorer, be sure to check the system clocks on both your
624 server and client machines. Internet Explorer is very picky about
625 timestamps for cookies. Note that you can quickly sync an Ubuntu
626 system with the following command:
628 sudo ntpdate ntp.ubuntu.com
630 Now trying going to L<http://localhost:3000/books/list> and you should
631 be redirected to the login page, hitting Shift+Reload if necessary (the
632 "You are already logged in" message should I<not> appear -- if it does,
633 click the C<logout> button and try again). Note the C<***Root::auto User
634 not found...> debug message in the development server output. Enter
635 username C<test01> and password C<mypass>, and you should be taken to
638 Open C<root/src/books/list.tt2> and add the following lines to the
639 bottom (below the closing </table> tag):
642 <a href="[% c.uri_for('/login') %]">Login</a>
643 <a href="[% c.uri_for('form_create') %]">Create</a>
646 Reload your browser and you should now see a "Login" and "Create" links
647 at the bottom of the page (as mentioned earlier, you can update template
648 files without reloading the development server). Click the first link
649 to return to the login page. This time you I<should> see the "You are
650 already logged in" message.
652 Finally, click the C<You can logout here> link on the C</login> page.
653 You should stay at the login page, but the message should change to "You
654 need to log in to use this application."
657 =head1 USING PASSWORD HASHES
659 In this section we increase the security of our system by converting
660 from cleartext passwords to SHA-1 password hashes.
662 B<Note:> This section is optional. You can skip it and the rest of the
663 tutorial will function normally.
665 Note that even with the techniques shown in this section, the browser
666 still transmits the passwords in cleartext to your application. We are
667 just avoiding the I<storage> of cleartext passwords in the database by
668 using a SHA-1 hash. If you are concerned about cleartext passwords
669 between the browser and your application, consider using SSL/TLS, made
670 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
673 =head2 Get a SHA-1 Hash for the Password
675 Catalyst uses the C<Digest> module to support a variety of hashing
676 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
677 First, we should compute the SHA-1 hash for the "mypass" password we are
678 using. The following command-line Perl script provides a "quick and
679 dirty" way to do this:
681 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
682 e727d1464ae12436e899a726da5b2f11d8381b26
685 B<Note:> If you are following along in Ubuntu, you will need to install
686 C<Digest::SHA> with the following command to run the example code above:
688 sudo aptitude install libdigest-sha-perl
690 B<Note:> You should probably modify this code for production use to
691 not read the password from the command line. By having the script
692 prompt for the cleartext password, it avoids having the password linger
693 in forms such as your C<.bash_history> files (assuming you are using
694 BASH as your shell). An example of such a script can be found in
698 =head2 Switch to SHA-1 Password Hashes in the Database
700 Next, we need to change the C<password> column of our C<users> table to
701 store this hash value vs. the existing cleartext password. Open
702 C<myapp03.sql> in your editor and enter:
705 -- Convert passwords to SHA-1 hashes
707 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
708 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
709 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
711 Then use the following command to update the SQLite database:
713 $ sqlite3 myapp.db < myapp03.sql
715 B<Note:> We are using SHA-1 hashes here, but many other hashing
716 algorithms are supported. See C<Digest> for more information.
719 =head2 Enable SHA-1 Hash Passwords in
720 C<Catalyst::Plugin::Authentication::Store::DBIC>
722 Edit C<myapp.conf> and update it to match (the C<password_type> and
723 C<password_hash_type> are new, everything else is the same):
731 # Note this first definition would be the same as setting
732 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
733 # ->{credential} = 'Password' in lib/MyApp.pm
735 # Specify that we are going to do password-based auth
737 # This is the name of the field in the users table with the
738 # password stored in it
739 password_field password
740 # Switch to more secure hashed passwords
742 # Use the SHA-1 hashing algorithm
743 password_hash_type SHA-1
746 # Use DBIC to retrieve username, password & role information
748 # This is the model object created by Catalyst::Model::DBIC
749 # from your schema (you created 'MyApp::Schema::User' but as
750 # the Catalyst startup debug messages show, it was loaded as
751 # 'MyApp::Model::DB::Users').
752 # NOTE: Omit 'MyApp::Model' here just as you would when using
753 # '$c->model("DB::Users)'
755 # This is the name of the field in your 'users' table that
756 # contains the user's name
763 =head2 Try Out the Hashed Passwords
765 Press C<Ctrl-C> to kill the previous server instance (if it's still
766 running) and restart it:
768 $ script/myapp_server.pl
770 You should now be able to go to L<http://localhost:3000/books/list> and
771 login as before. When done, click the "Logout" link on the login page
772 (or point your browser at L<http://localhost:3000/logout>).
775 =head1 USING THE SESSION FOR FLASH
777 As discussed in Part 3 of the tutorial, C<flash> allows you to set
778 variables in a way that is very similar to C<stash>, but it will
779 remain set across multiple requests. Once the value is read, it
780 is cleared (unless reset). Although C<flash> has nothing to do with
781 authentication, it does leverage the same session plugins. Now that
782 those plugins are enabled, let's go back and improve the "delete
783 and redirect with query parameters" code seen at the end of the
784 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
787 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
788 to match the following (everything after the model search line of code
798 # $id = primary key of book to delete
799 my ($self, $c, $id) = @_;
801 # Search for the book and then delete it
802 $c->model('DB::Books')->search({id => $id})->delete_all;
804 # Use 'flash' to save information across requests until it's read
805 $c->flash->{status_msg} = "Book deleted";
807 # Redirect the user back to the list page
808 $c->response->redirect($c->uri_for('/books/list'));
811 Next, open C<root/lib/site/layout> and update the TT code to pull from
812 flash vs. the C<status_msg> query parameter:
814 <div id="header">[% PROCESS site/header %]</div>
817 <span class="message">[% status_msg || c.flash.status_msg %]</span>
818 <span class="error">[% error_msg %]</span>
822 <div id="footer">[% PROCESS site/footer %]</div>
827 Restart the development server and point your browser to
828 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
829 several books. Click the "Return to list" link and delete one of the
830 "Test" books you just added. The C<flash> mechanism should retain our
831 "Book deleted" status message across the redirect.
833 B<NOTE:> While C<flash> will save information across multiple requests,
834 I<it does get cleared the first time it is read>. In general, this is
835 exactly what you want -- the C<flash> message will get displayed on
836 the next screen where it's appropriate, but it won't "keep showing up"
837 after that first time (unless you reset it). Please refer to
838 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
841 =head2 Switch To Flash-To-Stash
843 Although the a use of flash above is certainly an improvement over the
844 C<status_msg> we employed in Part 4 of the tutorial, the C<status_msg
845 || c.flash.status_msg> statement is a little ugly. A nice
846 alternative is to use the C<flash_to_stash> feature that automatically
847 copies the content of flash to stash. This makes your code controller
848 and template code work regardless of where it was directly access, a
849 forward, or a redirect. To enable C<flash_to_stash>, you can either
850 set the value in C<lib/MyApp.pm> by changing the default
851 C<__PACKAGE__-E<gt>config> setting to something like:
855 session => {flash_to_stash => 1}
858 B<or> add the following to C<myapp.conf>:
864 The C<__PACKAGE__-E<gt>config> option is probably preferable here
865 since it's not something you will want to change at runtime without it
866 possibly breaking some of your code.
868 Then edit C<root/lib/site/layout> and change the C<status_msg> line
869 to look like the following:
871 <span class="message">[% status_msg %]</span>
873 Restart the development server and go to
874 L<http://localhost:3000/books/list> in your browser. Delete another
875 of the "Test" books you added in the previous step. Flash should still
876 maintain the status message across the redirect even though you are no
877 longer explicitly accessing C<c.flash>.
882 Kennedy Clark, C<hkclark@gmail.com>
884 Please report any errors, issues or suggestions to the author. The
885 most recent version of the Catalyst Tutorial can be found at
886 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
888 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
889 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).