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 5). 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 simple tells DBIC to
208 load all of the result source 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 source" 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
297 a version of Catalyst earlier than v5.7014, delete the C<myapp.yml>
298 file and simply follow the directions below to create a new
301 Here, we need to load several parameters that tell
302 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
303 where to locate information in your database. To do this, edit the
304 C<myapp.conf> file and update it to match:
312 # Note this first definition would be the same as setting
313 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
314 # ->{credential} = 'Password' in lib/MyApp.pm
316 # Specify that we are going to do password-based auth
318 # This is the name of the field in the users table with the
319 # password stored in it
320 password_field password
321 # We are using an unencrypted password now
325 # Use DBIC to retrieve username, password & role information
327 # This is the model object created by Catalyst::Model::DBIC
328 # from your schema (you created 'MyApp::Schema::User' but as
329 # the Catalyst startup debug messages show, it was loaded as
330 # 'MyApp::Model::DB::Users').
331 # NOTE: Omit 'MyApp::Model' here just as you would when using
332 # '$c->model("DB::Users)'
334 # This is the name of the field in your 'users' table that
335 # contains the user's name
342 Inline comments in the code above explain how each field is being used.
344 Note that you can use many other config file formats with catalyst.
345 See L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
348 =head2 Add Login and Logout Controllers
350 Use the Catalyst create script to create two stub controller files:
352 $ script/myapp_create.pl controller Login
353 $ script/myapp_create.pl controller Logout
355 B<NOTE:> You could easily use a single controller here. For example,
356 you could have a C<User> controller with both C<login> and C<logout>
357 actions. Remember, Catalyst is designed to be very flexible, and leaves
358 such matters up to you, the designer and programmer.
360 Then open C<lib/MyApp/Controller/Login.pm>, locate the C<sub index
361 :Path :Args(0)> method (or C<sub index : Private> if you are using an
362 older version of Catalyst) that was automatically inserted by the
363 helpers when we created the Login controller above, and delete this
366 $c->response->body('Matched MyApp::Controller::Login in Login.');
368 Then update it to match:
376 sub index :Path :Args(0) {
379 # Get the username and password from form
380 my $username = $c->request->params->{username} || "";
381 my $password = $c->request->params->{password} || "";
383 # If the username and password values were found in form
384 if ($username && $password) {
385 # Attempt to log the user in
386 if ($c->authenticate({ username => $username,
387 password => $password} )) {
388 # If successful, then let them use the application
389 $c->response->redirect($c->uri_for('/books/list'));
392 # Set an error message
393 $c->stash->{error_msg} = "Bad username or password.";
397 # If either of above don't work out, send to the login page
398 $c->stash->{template} = 'login.tt2';
401 This controller fetches the C<username> and C<password> values from the
402 login form and attempts to authenticate the user. If successful, it
403 redirects the user to the book list page. If the login fails, the user
404 will stay at the login page but receive an error message. If the
405 C<username> and C<password> values are not present in the form, the
406 user will be taken to the empty login form.
408 Note that we could have used something like C<sub default :Path>,
409 however partly for historical reasons, and partly for code clarity it
410 is generally recommended only to use C<default> in
411 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
412 found page for the application.
414 Instead, we are using C<sub base :Path :Args(0) {...}> here to
415 specifically match the URL C</login>. C<Path> actions (aka, "literal
416 actions") create URI matches relative to the namespace of the
417 controller where they are defined. Although C<Path> supports
418 arguments that allow relative and absolute paths to be defined, here
419 we use an empty C<Path> definition to match on just the name of the
420 controller itself. The method name, C<index>, is arbitrary. We make
421 the match even more specific with the C<:Args(0)> action modifier --
422 this forces the match on I<only> C</login>, not
423 C</login/somethingelse>.
425 Next, update the corresponding method in
426 C<lib/MyApp/Controller/Logout.pm> to match:
434 sub index :Path :Args(0) {
437 # Clear the user's state
440 # Send the user to the starting point
441 $c->response->redirect($c->uri_for('/'));
444 As with the login controller, be sure to delete the
445 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
446 line of the C<sub index>.
449 =head2 Add a Login Form TT Template Page
451 Create a login form by opening C<root/src/login.tt2> and inserting:
453 [% META title = 'Login' %]
456 <form method="post" action=" [% Catalyst.uri_for('/login') %] ">
460 <td><input type="text" name="username" size="40" /></td>
464 <td><input type="password" name="password" size="40" /></td>
467 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
473 =head2 Add Valid User Check
475 We need something that provides enforcement for the authentication
476 mechanism -- a I<global> mechanism that prevents users who have not
477 passed authentication from reaching any pages except the login page.
478 This is generally done via an C<auto> action/method (prior to Catalyst
479 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
480 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
482 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
483 the following method:
487 Check if there is a user and, if not, forward to login page
491 # Note that 'auto' runs after 'begin' but before your actions and that
492 # 'auto' "chain" (all from application path to most specific class are run)
493 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
497 # Allow unauthenticated users to reach the login page. This
498 # allows anauthenticated users to reach any action in the Login
499 # controller. To lock it down to a single action, we could use:
500 # if ($c->action eq $c->controller('Login')->action_for('index'))
501 # to only allow unauthenticated access to the C<index> action we
503 if ($c->controller eq $c->controller('Login')) {
507 # If a user doesn't exist, force login
508 if (!$c->user_exists) {
509 # Dump a log message to the development server debug output
510 $c->log->debug('***Root::auto User not found, forwarding to /login');
511 # Redirect the user to the login page
512 $c->response->redirect($c->uri_for('/login'));
513 # Return 0 to cancel 'post-auto' processing and prevent use of application
517 # User found, so return 1 to continue with processing after this 'auto'
522 B<Note:> Catalyst provides a number of different types of actions,
523 such as C<Local>, C<Regex>, C<Private> and the new C<Path>. You
524 should refer to L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> for
525 a more detailed explanation, but the following bullet points provide a
532 The majority of application have traditionally use C<Local> actions
533 for items that respond to user requests and C<Private> actions for
534 those that do not directly respond to user input.
538 Newer Catalyst applications tend to use C<Path> actions and the
539 C<Args> attribute because of their power and flexibility. You can
540 specify the path to match relative to the namespace of the current
541 module as an argument to C<Path>. For example C<Path('list')> in
542 C<lib/MyApp/Controller/Books.pm> would match on the URL
543 C<http://localhost:3000/books/list> but C<Path('/list')> would
544 match on C<http://localhost:3000/list>.
548 Automatic "chaining" of actions by the dispatcher is a powerful
549 feature that allows multiple methods to handle a single URL. See
550 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
551 for more information on chained actions.
555 There are five types of build-in C<Private> actions: C<begin>, C<end>,
556 C<default>, C<index>, and C<auto>.
560 With C<begin>, C<end>, C<default>, C<index> private actions, only the
561 most specific action of each type will be called. For example, if you
562 define a C<begin> action in your controller it will I<override> a
563 C<begin> action in your application/root controller -- I<only> the
564 action in your controller will be called.
568 Unlike the other actions where only a single method is called for each
569 request, I<every> auto action along the chain of namespaces will be
570 called. Each C<auto> action will be called I<from the application/root
571 controller down through the most specific class>.
575 By placing the authentication enforcement code inside the C<auto> method
576 of C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
577 called for I<every> request that is received by the entire application.
580 =head2 Displaying Content Only to Authenticated Users
582 Let's say you want to provide some information on the login page that
583 changes depending on whether the user has authenticated yet. To do
584 this, open C<root/src/login.tt2> in your editor and add the following
585 lines to the bottom of the file:
589 # This code illustrates how certain parts of the TT
590 # template will only be shown to users who have logged in
592 [% IF Catalyst.user_exists %]
593 Please Note: You are already logged in as '[% Catalyst.user.username %]'.
594 You can <a href="[% Catalyst.uri_for('/logout') %]">logout</a> here.
596 You need to log in to use this application.
599 Note that this whole block is a comment because the "#" appears
600 immediate after the "[%" (with no spaces in between). Although it
601 can be a handy way to temporarily "comment out" a whole block of
602 TT code, it's probably a little too subtle for use in "normal"
607 Although most of the code is comments, the middle few lines provide a
608 "you are already logged in" reminder if the user returns to the login
609 page after they have already authenticated. For users who have not yet
610 authenticated, a "You need to log in..." message is displayed (note the
611 use of an IF-THEN-ELSE construct in TT).
614 =head2 Try Out Authentication
616 Press C<Ctrl-C> to kill the previous server instance (if it's still
617 running) and restart it:
619 $ script/myapp_server.pl
621 B<IMPORTANT NOTE:> If you are having issues with authentication on
622 Internet Explorer, be sure to check the system clocks on both your
623 server and client machines. Internet Explorer is very picky about
624 timestamps for cookies. Note that you can quickly sync an Ubuntu
625 system with the following command:
627 sudo ntpdate ntp.ubuntu.com
629 Now trying going to L<http://localhost:3000/books/list> and you should
630 be redirected to the login page, hitting Shift+Reload if necessary (the
631 "You are already logged in" message should I<not> appear -- if it does,
632 click the C<logout> button and try again). Note the C<***Root::auto User
633 not found...> debug message in the development server output. Enter
634 username C<test01> and password C<mypass>, and you should be taken to
637 Open C<root/src/books/list.tt2> and add the following lines to the
638 bottom (below the closing </table> tag):
641 <a href="[% Catalyst.uri_for('/login') %]">Login</a>
642 <a href="[% Catalyst.uri_for('form_create') %]">Create</a>
645 Reload your browser and you should now see a "Login" and "Create" links
646 at the bottom of the page (as mentioned earlier, you can update template
647 files without reloading the development server). Click the first link
648 to return to the login page. This time you I<should> see the "You are
649 already logged in" message.
651 Finally, click the C<You can logout here> link on the C</login> page.
652 You should stay at the login page, but the message should change to "You
653 need to log in to use this application."
656 =head1 USING PASSWORD HASHES
658 In this section we increase the security of our system by converting
659 from cleartext passwords to SHA-1 password hashes.
661 B<Note:> This section is optional. You can skip it and the rest of the
662 tutorial will function normally.
664 Note that even with the techniques shown in this section, the browser
665 still transmits the passwords in cleartext to your application. We are
666 just avoiding the I<storage> of cleartext passwords in the database by
667 using a SHA-1 hash. If you are concerned about cleartext passwords
668 between the browser and your application, consider using SSL/TLS, made
669 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
672 =head2 Get a SHA-1 Hash for the Password
674 Catalyst uses the C<Digest> module to support a variety of hashing
675 algorithms. Here we will use SHA-1 (SHA = Secure Hash Algorithm).
676 First, we should compute the SHA-1 hash for the "mypass" password we are
677 using. The following command-line Perl script provides a "quick and
678 dirty" way to do this:
680 $ perl -MDigest::SHA -e 'print Digest::SHA::sha1_hex("mypass"), "\n"'
681 e727d1464ae12436e899a726da5b2f11d8381b26
684 B<Note:> If you are following along in Ubuntu, you will need to install
685 C<Digest::SHA> with the following command to run the example code above:
687 sudo apt-get install libdigest-sha-perl
689 B<Note:> You should probably modify this code for production use to
690 not read the password from the command line. By having the script
691 prompt for the cleartext password, it avoids having the password linger
692 in forms such as your C<.bash_history> files (assuming you are using
693 BASH as your shell). An example of such a script can be found in
697 =head2 Switch to SHA-1 Password Hashes in the Database
699 Next, we need to change the C<password> column of our C<users> table to
700 store this hash value vs. the existing cleartext password. Open
701 C<myapp03.sql> in your editor and enter:
704 -- Convert passwords to SHA-1 hashes
706 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 1;
707 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 2;
708 UPDATE users SET password = 'e727d1464ae12436e899a726da5b2f11d8381b26' WHERE id = 3;
710 Then use the following command to update the SQLite database:
712 $ sqlite3 myapp.db < myapp03.sql
714 B<Note:> We are using SHA-1 hashes here, but many other hashing
715 algorithms are supported. See C<Digest> for more information.
718 =head2 Enable SHA-1 Hash Passwords in
719 C<Catalyst::Plugin::Authentication::Store::DBIC>
721 Edit C<myapp.conf> and update it to match (the C<password_type> and
722 C<password_hash_type> are new, everything else is the same):
730 # Note this first definition would be the same as setting
731 # __PACKAGE__->config->{authentication}->{realms}->{dbic}
732 # ->{credential} = 'Password' in lib/MyApp.pm
734 # Specify that we are going to do password-based auth
736 # This is the name of the field in the users table with the
737 # password stored in it
738 password_field password
739 # Switch to more secure hashed passwords
741 # Use the SHA-1 hashing algorithm
742 password_hash_type SHA-1
745 # Use DBIC to retrieve username, password & role information
747 # This is the model object created by Catalyst::Model::DBIC
748 # from your schema (you created 'MyApp::Schema::User' but as
749 # the Catalyst startup debug messages show, it was loaded as
750 # 'MyApp::Model::DB::Users').
751 # NOTE: Omit 'MyApp::Model' here just as you would when using
752 # '$c->model("DB::Users)'
754 # This is the name of the field in your 'users' table that
755 # contains the user's name
762 =head2 Try Out the Hashed Passwords
764 Press C<Ctrl-C> to kill the previous server instance (if it's still
765 running) and restart it:
767 $ script/myapp_server.pl
769 You should now be able to go to L<http://localhost:3000/books/list> and
770 login as before. When done, click the "Logout" link on the login page
771 (or point your browser at L<http://localhost:3000/logout>).
774 =head1 USING THE SESSION FOR FLASH
776 As discussed in Part 3 of the tutorial, C<flash> allows you to set
777 variables in a way that is very similar to C<stash>, but it will
778 remain set across multiple requests. Once the value is read, it
779 is cleared (unless reset). Although C<flash> has nothing to do with
780 authentication, it does leverage the same session plugins. Now that
781 those plugins are enabled, let's go back and improve the "delete
782 and redirect with query parameters" code seen at the end of the
783 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> part of the
786 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
787 to match the following (everything after the model search line of code
797 # $id = primary key of book to delete
798 my ($self, $c, $id) = @_;
800 # Search for the book and then delete it
801 $c->model('DB::Books')->search({id => $id})->delete_all;
803 # Use 'flash' to save information across requests until it's read
804 $c->flash->{status_msg} = "Book deleted";
806 # Redirect the user back to the list page
807 $c->response->redirect($c->uri_for('/books/list'));
810 Next, open C<root/lib/site/layout> and update the TT code to pull from
811 flash vs. the C<status_msg> query parameter:
813 <div id="header">[% PROCESS site/header %]</div>
816 <span class="message">[% status_msg || Catalyst.flash.status_msg %]</span>
817 <span class="error">[% error_msg %]</span>
821 <div id="footer">[% PROCESS site/footer %]</div>
826 Restart the development server and point your browser to
827 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
828 several books. Click the "Return to list" link and delete one of the
829 "Test" books you just added. The C<flash> mechanism should retain our
830 "Book deleted" status message across the redirect.
832 B<NOTE:> While C<flash> will save information across multiple requests,
833 I<it does get cleared the first time it is read>. In general, this is
834 exactly what you want -- the C<flash> message will get displayed on
835 the next screen where it's appropriate, but it won't "keep showing up"
836 after that first time (unless you reset it). Please refer to
837 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
840 =head2 Switch To Flash-To-Stash
842 Although the a use of flash above is certainly an improvement over the
843 C<status_msg> we employed in Part 4 of the tutorial, the C<status_msg
844 || Catalyst.flash.status_msg> statement is a little ugly. A nice
845 alternative is to use the C<flash_to_stash> feature that automatically
846 copies the content of flash to stash. This makes your code controller
847 and template code work regardless of where it was directly access, a
848 forward, or a redirect. To enable C<flash_to_stash>, you can either
849 set the value in C<lib/MyApp.pm> by changing the default
850 C<__PACKAGE__-E<gt>config> setting to something like:
854 session => {flash_to_stash => 1}
857 B<or> add the following to C<myapp.conf>:
863 The C<__PACKAGE__-E<gt>config> option is probably preferable here
864 since it's not something you will want to change at runtime without it
865 possibly breaking some of your code.
867 Then edit C<root/lib/site/layout> and change the C<status_msg> line
868 to look like the following:
870 <span class="message">[% status_msg %]</span>
872 Restart the development server and go to
873 L<http://localhost:3000/books/list> in your browser. Delete another
874 of the "Test" books you added in the previous step. Flash should still
875 maintain the status message across the redirect even though you are no
876 longer explicitly accessing C<Catalyst.flash>.
881 Kennedy Clark, C<hkclark@gmail.com>
883 Please report any errors, issues or suggestions to the author. The
884 most recent version of the Catalyst Tutorial can be found at
885 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
887 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
888 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).