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
319 deployment (or you could use a mixture: leave C<class> and
320 C<user_model> defined in C<lib/MyApp.pm> as we show above, but place
321 C<password_type> in C<myapp.conf> to allow the type of password to be
322 easily modified during deployment). We will stick with putting
323 all of the authentication-related configuration in C<lib/MyApp.pm>
324 for the tutorial, but if you wish to use C<myapp.conf>, just convert
325 to the following code:
327 <Plugin::Authentication>
330 password_type self_check
334 </Plugin::Authentication>
336 B<TIP:> Here is a short script that will dump the contents of
337 C<MyApp->config> to L<Config::General|Config::General> format in
340 $ perl -Ilib -e 'use MyApp; use Config::General;
341 Config::General->new->save_file("myapp.conf", MyApp->config);'
344 =head2 Add Login and Logout Controllers
346 Use the Catalyst create script to create two stub controller files:
348 $ script/myapp_create.pl controller Login
349 $ script/myapp_create.pl controller Logout
351 You could easily use a single controller here. For example, you could
352 have a C<User> controller with both C<login> and C<logout> actions.
353 Remember, Catalyst is designed to be very flexible, and leaves such
354 matters up to you, the designer and programmer.
356 Then open C<lib/MyApp/Controller/Login.pm>, locate the
357 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
358 are using an older version of Catalyst) that was automatically
359 inserted by the helpers when we created the Login controller above,
360 and update the definition of C<sub index> to match:
368 sub index :Path :Args(0) {
371 # Get the username and password from form
372 my $username = $c->request->params->{username} || "";
373 my $password = $c->request->params->{password} || "";
375 # If the username and password values were found in form
376 if ($username && $password) {
377 # Attempt to log the user in
378 if ($c->authenticate({ username => $username,
379 password => $password } )) {
380 # If successful, then let them use the application
381 $c->response->redirect($c->uri_for(
382 $c->controller('Books')->action_for('list')));
385 # Set an error message
386 $c->stash->{error_msg} = "Bad username or password.";
390 # If either of above don't work out, send to the login page
391 $c->stash->{template} = 'login.tt2';
394 This controller fetches the C<username> and C<password> values from the
395 login form and attempts to authenticate the user. If successful, it
396 redirects the user to the book list page. If the login fails, the user
397 will stay at the login page and receive an error message. If the
398 C<username> and C<password> values are not present in the form, the
399 user will be taken to the empty login form.
401 Note that we could have used something like "C<sub default :Path>",
402 however, it is generally recommended (partly for historical reasons,
403 and partly for code clarity) only to use C<default> in
404 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
405 found page for the application.
407 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
408 specifically match the URL C</login>. C<Path> actions (aka, "literal
409 actions") create URI matches relative to the namespace of the
410 controller where they are defined. Although C<Path> supports
411 arguments that allow relative and absolute paths to be defined, here
412 we use an empty C<Path> definition to match on just the name of the
413 controller itself. The method name, C<index>, is arbitrary. We make
414 the match even more specific with the C<:Args(0)> action modifier --
415 this forces the match on I<only> C</login>, not
416 C</login/somethingelse>.
418 Next, update the corresponding method in
419 C<lib/MyApp/Controller/Logout.pm> to match:
427 sub index :Path :Args(0) {
430 # Clear the user's state
433 # Send the user to the starting point
434 $c->response->redirect($c->uri_for('/'));
437 As with the login controller, be sure to delete the
438 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
439 line of the C<sub index>.
442 =head2 Add a Login Form TT Template Page
444 Create a login form by opening C<root/src/login.tt2> and inserting:
446 [% META title = 'Login' %]
449 <form method="post" action="[% c.uri_for('/login') %]">
453 <td><input type="text" name="username" size="40" /></td>
457 <td><input type="password" name="password" size="40" /></td>
460 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
466 =head2 Add Valid User Check
468 We need something that provides enforcement for the authentication
469 mechanism -- a I<global> mechanism that prevents users who have not
470 passed authentication from reaching any pages except the login page.
471 This is generally done via an C<auto> action/method (prior to Catalyst
472 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
473 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
475 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
476 the following method:
480 Check if there is a user and, if not, forward to login page
484 # Note that 'auto' runs after 'begin' but before your actions and that
485 # 'auto's "chain" (all from application path to most specific class are run)
486 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
490 # Allow unauthenticated users to reach the login page. This
491 # allows unauthenticated users to reach any action in the Login
492 # controller. To lock it down to a single action, we could use:
493 # if ($c->action eq $c->controller('Login')->action_for('index'))
494 # to only allow unauthenticated access to the 'index' action we
496 if ($c->controller eq $c->controller('Login')) {
500 # If a user doesn't exist, force login
501 if (!$c->user_exists) {
502 # Dump a log message to the development server debug output
503 $c->log->debug('***Root::auto User not found, forwarding to /login');
504 # Redirect the user to the login page
505 $c->response->redirect($c->uri_for('/login'));
506 # Return 0 to cancel 'post-auto' processing and prevent use of application
510 # User found, so return 1 to continue with processing after this 'auto'
515 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
516 every C<auto> method from the application/root controller down to the
517 most specific controller will be called. By placing the
518 authentication enforcement code inside the C<auto> method of
519 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
520 called for I<every> request that is received by the entire
524 =head2 Displaying Content Only to Authenticated Users
526 Let's say you want to provide some information on the login page that
527 changes depending on whether the user has authenticated yet. To do
528 this, open C<root/src/login.tt2> in your editor and add the following
529 lines to the bottom of the file:
534 # This code illustrates how certain parts of the TT
535 # template will only be shown to users who have logged in
537 [% IF c.user_exists %]
538 Please Note: You are already logged in as '[% c.user.username %]'.
539 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
541 You need to log in to use this application.
544 Note that this whole block is a comment because the "#" appears
545 immediate after the "[%" (with no spaces in between). Although it
546 can be a handy way to temporarily "comment out" a whole block of
547 TT code, it's probably a little too subtle for use in "normal"
552 Although most of the code is comments, the middle few lines provide a
553 "you are already logged in" reminder if the user returns to the login
554 page after they have already authenticated. For users who have not yet
555 authenticated, a "You need to log in..." message is displayed (note the
556 use of an IF-THEN-ELSE construct in TT).
559 =head2 Try Out Authentication
561 Press C<Ctrl-C> to kill the previous server instance (if it's still
562 running) and restart it:
564 $ script/myapp_server.pl
566 B<IMPORTANT NOTE:> If you are having issues with authentication on
567 Internet Explorer, be sure to check the system clocks on both your
568 server and client machines. Internet Explorer is very picky about
569 timestamps for cookies. You can quickly sync a Debian system by
570 installing the "ntpdate" package:
572 sudo aptitude -y install ntpdate
574 And then run the following command:
578 Or, depending on your firewall configuration:
580 sudo ntpdate-debian -u
582 Note: NTP can be a little more finicky about firewalls because it uses
583 UDP vs. the more common TCP that you see with most Internet protocols.
584 Worse case, you might have to manually set the time on your development
585 box instead of using NTP.
587 Now trying going to L<http://localhost:3000/books/list> and you should
588 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
589 if necessary (the "You are already logged in" message should I<not>
590 appear -- if it does, click the C<logout> button and try again). Note
591 the C<***Root::auto User not found...> debug message in the
592 development server output. Enter username C<test01> and password
593 C<mypass>, and you should be taken to the Book List page.
595 Open C<root/src/books/list.tt2> and add the following lines to the
596 bottom (below the closing </table> tag):
599 <a href="[% c.uri_for('/login') %]">Login</a>
600 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
603 Reload your browser and you should now see a "Login" and "Create" links
604 at the bottom of the page (as mentioned earlier, you can update template
605 files without reloading the development server). Click the first link
606 to return to the login page. This time you I<should> see the "You are
607 already logged in" message.
609 Finally, click the C<You can logout here> link on the C</login> page.
610 You should stay at the login page, but the message should change to "You
611 need to log in to use this application."
614 =head1 USING PASSWORD HASHES
616 In this section we increase the security of our system by converting
617 from cleartext passwords to SHA-1 password hashes that include a
618 random "salt" value to make them extremely difficult to crack with
619 dictionary and "rainbow table" attacks.
621 B<Note:> This section is optional. You can skip it and the rest of the
622 tutorial will function normally.
624 Be aware that even with the techniques shown in this section, the browser
625 still transmits the passwords in cleartext to your application. We are
626 just avoiding the I<storage> of cleartext passwords in the database by
627 using a salted SHA-1 hash. If you are concerned about cleartext passwords
628 between the browser and your application, consider using SSL/TLS, made
629 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
632 =head2 Install DBIx::Class::EncodedColumn
634 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> provides features
635 that can greatly simplify the maintenance of passwords. It's currently
636 not available as a .deb package in the normal Debian repositories, so let's
637 install it directly from CPAN:
639 $ sudo cpan DBIx::Class::EncodedColumn
642 =head2 Re-Run the DBIC::Schema Model Helper to Include DBIx::Class::EncodedColumn
644 Next, we can re-run the model helper to have it include
645 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> in all of the
646 Result Classes it generates for us. Simply use the same command we
647 saw in Chapters 3 and 4, but add C<,EncodedColumn> to the C<components>
650 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
651 create=static components=TimeStamp,EncodedColumn dbi:SQLite:myapp.db
653 If you then open one of the Result Classes, you will see that it
654 includes EncodedColumn in the C<load_components> line. Take a look at
655 C<lib/MyApp/Schema/Result/Users.pm> since that's the main class where we
656 want to use hashed and salted passwords:
658 __PACKAGE__->load_components("InflateColumn::DateTime", "TimeStamp", "EncodedColumn", "Core");
661 =head2 Modify the "password" Column to Use EncodedColumn
663 Open the file C<lib/MyApp/Schema/Result/Users.pm> and enter the following
664 text below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" line but above
667 # Have the 'password' column use a SHA-1 hash and 10-character salt
668 # with hex encoding; Generate the 'check_password" method
669 __PACKAGE__->add_columns(
674 encode_class => 'Digest',
675 encode_args => {salt_length => 10},
676 encode_check_method => 'check_password',
680 This redefines the automatically generated definition for the password
681 fields at the top of the Result Class file to now use EncodedColumn
682 logic (C<encoded_column> is set to 1). C<encode_class> can be set to
683 either C<Digest> to use
684 L<DBIx::Class::EncodedColumn::Digest|DBIx::Class::EncodedColumn::Digest>,
685 or C<Crypt::Eksblowfish::Bcrypt> for
686 L<DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt|DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt>.
687 C<encode_args> is then used to customize the type of Digest you
688 selected. Here we only specified the size of the salt to use, but
689 we could have also modified the hashing algorithm ('SHA-256' is
690 the default) and the format to use ('base64' is the default, but
691 'hex' and 'binary' are other options). To use these, you could
692 change the C<encode_args> to something like:
694 encode_args => {algorithm => 'SHA-1',
699 =head2 Load Hashed Passwords in the Database
701 Next, let's create a quick script to load some hashed and salted passwords
702 into the C<password> column of our C<users> table. Open the file
703 C<set_hashed_passwords.pl> in your editor and enter the following text:
712 my $schema = MyApp::Schema->connect('dbi:SQLite:myapp.db');
714 my @users = $schema->resultset('Users')->all;
716 foreach my $user (@users) {
717 $user->password('mypass');
721 EncodedColumn lets us simple call C<$user->check_password($password)>
722 to see if the user has supplied the correct password, or, as we show
723 above, call C<$user->update($new_password)> to update the hashed
724 password stored for this user.
726 Then run the following command:
728 $ perl -Ilib set_hashed_passwords.pl
730 We had to use the C<-Ilib> arguement to tell perl to look under the
731 C<lib> directory for our C<MyApp::Schema> model.
733 Then dump the users table to verify that it worked:
735 $ sqlite3 myapp.db "select * from users"
736 1|test01|38d3974fa9e9263099f7bc2574284b2f55473a9bM=fwpX2NR8|t01@na.com|Joe|Blow|1
737 2|test02|6ed8586587e53e0d7509b1cfed5df08feadc68cbMJlnPyPt0I|t02@na.com|Jane|Doe|1
738 3|test03|af929a151340c6aed4d54d7e2651795d1ad2e2f7UW8dHoGv9z|t03@na.com|No|Go|0
740 As you can see, the passwords are much harder to steal from the
741 database. Also note that this demonstrates how to use a DBIx::Class
742 model outside of your web application -- a very useful feature in many
746 =head2 Enable Hashed and Salted Passwords
748 Edit C<lib/MyApp.pm> and update it to match the following text (the only change
749 is to the C<password_type> field):
751 # Configure SimpleDB Authentication
752 __PACKAGE__->config->{'Plugin::Authentication'} = {
755 user_model => 'DB::Users',
756 password_type => 'self_check',
760 The use of C<self_check> will cause
761 Catalyst::Plugin::Authentication::Store::DBIC to call the
762 C<check_password> method we enabled on our C<password> columns.
765 =head2 Try Out the Hashed Passwords
767 Press C<Ctrl-C> to kill the previous server instance (if it's still
768 running) and restart it:
770 $ script/myapp_server.pl
772 You should now be able to go to L<http://localhost:3000/books/list> and
773 login as before. When done, click the "logout" link on the login page
774 (or point your browser at L<http://localhost:3000/logout>).
777 =head1 USING THE SESSION FOR FLASH
779 As discussed in the previous chapter of the tutorial, C<flash> allows
780 you to set variables in a way that is very similar to C<stash>, but it
781 will remain set across multiple requests. Once the value is read, it
782 is cleared (unless reset). Although C<flash> has nothing to do with
783 authentication, it does leverage the same session plugins. Now that
784 those plugins are enabled, let's go back and update the "delete and
785 redirect with query parameters" code seen at the end of the L<Basic
786 CRUD|Catalyst::Manual::Tutorial::BasicCRUD> chapter of the tutorial to
787 take advantage of C<flash>.
789 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
790 to match the following (everything after the model search line of code
799 sub delete :Chained('object') :PathPart('delete') :Args(0) {
802 # Use the book object saved by 'object' and delete it along
803 # with related 'book_authors' entries
804 $c->stash->{object}->delete;
806 # Use 'flash' to save information across requests until it's read
807 $c->flash->{status_msg} = "Book deleted";
809 # Redirect the user back to the list page
810 $c->response->redirect($c->uri_for($self->action_for('list')));
813 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
814 flash vs. the C<status_msg> query parameter:
818 [%# Status and error messages %]
819 <span class="message">[% status_msg || c.flash.status_msg %]</span>
820 <span class="error">[% error_msg %]</span>
821 [%# This is where TT will stick all of your template's contents. -%]
823 </div><!-- end content -->
826 Although the sample above only shows the C<content> div, leave the
827 rest of the file intact -- the only change we made to the C<wrapper.tt2>
828 was to add "C<|| c.request.params.status_msg>" to the
829 C<E<lt>span class="message"E<gt>> line.
834 Restart the development server, log in, and then point your browser to
835 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
836 several books. Click the "Return to list" link and delete one of the
837 "Test" books you just added. The C<flash> mechanism should retain our
838 "Book deleted" status message across the redirect.
840 B<NOTE:> While C<flash> will save information across multiple requests,
841 I<it does get cleared the first time it is read>. In general, this is
842 exactly what you want -- the C<flash> message will get displayed on
843 the next screen where it's appropriate, but it won't "keep showing up"
844 after that first time (unless you reset it). Please refer to
845 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
849 =head2 Switch To Flash-To-Stash
851 Although the a use of flash above works well, the
852 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
853 alternative is to use the C<flash_to_stash> feature that automatically
854 copies the content of flash to stash. This makes your controller
855 and template code work regardless of where it was directly access, a
856 forward, or a redirect. To enable C<flash_to_stash>, you can either
857 set the value in C<lib/MyApp.pm> by changing the default
858 C<__PACKAGE__-E<gt>config> setting to something like:
862 session => {flash_to_stash => 1}
865 B<or> add the following to C<myapp.conf>:
871 The C<__PACKAGE__-E<gt>config> option is probably preferable here
872 since it's not something you will want to change at runtime without it
873 possibly breaking some of your code.
875 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
876 to match the following:
878 <span class="message">[% status_msg %]</span>
880 Restart the development server and go to
881 L<http://localhost:3000/books/list> in your browser. Delete another
882 of the "Test" books you added in the previous step. Flash should still
883 maintain the status message across the redirect even though you are no
884 longer explicitly accessing C<c.flash>.
889 Kennedy Clark, C<hkclark@gmail.com>
891 Please report any errors, issues or suggestions to the author. The
892 most recent version of the Catalyst Tutorial can be found at
893 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
895 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
896 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).