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);'
343 B<NOTE:> Because we are using SimpleDB along with a database layout
344 that complies with its default assumptions, we don't need to specify
345 the names of the columns where our username and password information
346 is stored (hence, the "Simple" part of "SimpleDB"). That being said,
347 SimpleDB let's you specify that type of information if you need to.
349 C<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
353 =head2 Add Login and Logout Controllers
355 Use the Catalyst create script to create two stub controller files:
357 $ script/myapp_create.pl controller Login
358 $ script/myapp_create.pl controller Logout
360 You could easily use a single controller here. For example, you could
361 have a C<User> controller with both C<login> and C<logout> actions.
362 Remember, Catalyst is designed to be very flexible, and leaves such
363 matters up to you, the designer and programmer.
365 Then open C<lib/MyApp/Controller/Login.pm>, locate the
366 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
367 are using an older version of Catalyst) that was automatically
368 inserted by the helpers when we created the Login controller above,
369 and update the definition of C<sub index> 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(
391 $c->controller('Books')->action_for('list')));
394 # Set an error message
395 $c->stash->{error_msg} = "Bad username or password.";
399 # If either of above don't work out, send to the login page
400 $c->stash->{template} = 'login.tt2';
403 This controller fetches the C<username> and C<password> values from the
404 login form and attempts to authenticate the user. If successful, it
405 redirects the user to the book list page. If the login fails, the user
406 will stay at the login page and receive an error message. If the
407 C<username> and C<password> values are not present in the form, the
408 user will be taken to the empty login form.
410 Note that we could have used something like "C<sub default :Path>",
411 however, it is generally recommended (partly for historical reasons,
412 and partly for code clarity) only to use C<default> in
413 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
414 found page for the application.
416 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
417 specifically match the URL C</login>. C<Path> actions (aka, "literal
418 actions") create URI matches relative to the namespace of the
419 controller where they are defined. Although C<Path> supports
420 arguments that allow relative and absolute paths to be defined, here
421 we use an empty C<Path> definition to match on just the name of the
422 controller itself. The method name, C<index>, is arbitrary. We make
423 the match even more specific with the C<:Args(0)> action modifier --
424 this forces the match on I<only> C</login>, not
425 C</login/somethingelse>.
427 Next, update the corresponding method in
428 C<lib/MyApp/Controller/Logout.pm> to match:
436 sub index :Path :Args(0) {
439 # Clear the user's state
442 # Send the user to the starting point
443 $c->response->redirect($c->uri_for('/'));
446 As with the login controller, be sure to delete the
447 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
448 line of the C<sub index>.
451 =head2 Add a Login Form TT Template Page
453 Create a login form by opening C<root/src/login.tt2> and inserting:
455 [% META title = 'Login' %]
458 <form method="post" action="[% c.uri_for('/login') %]">
462 <td><input type="text" name="username" size="40" /></td>
466 <td><input type="password" name="password" size="40" /></td>
469 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
475 =head2 Add Valid User Check
477 We need something that provides enforcement for the authentication
478 mechanism -- a I<global> mechanism that prevents users who have not
479 passed authentication from reaching any pages except the login page.
480 This is generally done via an C<auto> action/method (prior to Catalyst
481 v5.66, this sort of thing would go in C<MyApp.pm>, but starting in
482 v5.66, the preferred location is C<lib/MyApp/Controller/Root.pm>).
484 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
485 the following method:
489 Check if there is a user and, if not, forward to login page
493 # Note that 'auto' runs after 'begin' but before your actions and that
494 # 'auto's "chain" (all from application path to most specific class are run)
495 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
499 # Allow unauthenticated users to reach the login page. This
500 # allows unauthenticated users to reach any action in the Login
501 # controller. To lock it down to a single action, we could use:
502 # if ($c->action eq $c->controller('Login')->action_for('index'))
503 # to only allow unauthenticated access to the 'index' action we
505 if ($c->controller eq $c->controller('Login')) {
509 # If a user doesn't exist, force login
510 if (!$c->user_exists) {
511 # Dump a log message to the development server debug output
512 $c->log->debug('***Root::auto User not found, forwarding to /login');
513 # Redirect the user to the login page
514 $c->response->redirect($c->uri_for('/login'));
515 # Return 0 to cancel 'post-auto' processing and prevent use of application
519 # User found, so return 1 to continue with processing after this 'auto'
524 L<Catalyst::Manual::Tutorial::MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
525 every C<auto> method from the application/root controller down to the
526 most specific controller will be called. By placing the
527 authentication enforcement code inside the C<auto> method of
528 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
529 called for I<every> request that is received by the entire
533 =head2 Displaying Content Only to Authenticated Users
535 Let's say you want to provide some information on the login page that
536 changes depending on whether the user has authenticated yet. To do
537 this, open C<root/src/login.tt2> in your editor and add the following
538 lines to the bottom of the file:
543 # This code illustrates how certain parts of the TT
544 # template will only be shown to users who have logged in
546 [% IF c.user_exists %]
547 Please Note: You are already logged in as '[% c.user.username %]'.
548 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
550 You need to log in to use this application.
553 Note that this whole block is a comment because the "#" appears
554 immediate after the "[%" (with no spaces in between). Although it
555 can be a handy way to temporarily "comment out" a whole block of
556 TT code, it's probably a little too subtle for use in "normal"
561 Although most of the code is comments, the middle few lines provide a
562 "you are already logged in" reminder if the user returns to the login
563 page after they have already authenticated. For users who have not yet
564 authenticated, a "You need to log in..." message is displayed (note the
565 use of an IF-THEN-ELSE construct in TT).
568 =head2 Try Out Authentication
570 Press C<Ctrl-C> to kill the previous server instance (if it's still
571 running) and restart it:
573 $ script/myapp_server.pl
575 B<IMPORTANT NOTE:> If you are having issues with authentication on
576 Internet Explorer, be sure to check the system clocks on both your
577 server and client machines. Internet Explorer is very picky about
578 timestamps for cookies. You can quickly sync a Debian system by
579 installing the "ntpdate" package:
581 sudo aptitude -y install ntpdate
583 And then run the following command:
587 Or, depending on your firewall configuration:
589 sudo ntpdate-debian -u
591 Note: NTP can be a little more finicky about firewalls because it uses
592 UDP vs. the more common TCP that you see with most Internet protocols.
593 Worse case, you might have to manually set the time on your development
594 box instead of using NTP.
596 Now trying going to L<http://localhost:3000/books/list> and you should
597 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
598 if necessary (the "You are already logged in" message should I<not>
599 appear -- if it does, click the C<logout> button and try again). Note
600 the C<***Root::auto User not found...> debug message in the
601 development server output. Enter username C<test01> and password
602 C<mypass>, and you should be taken to the Book List page.
604 Open C<root/src/books/list.tt2> and add the following lines to the
605 bottom (below the closing </table> tag):
608 <a href="[% c.uri_for('/login') %]">Login</a>
609 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
612 Reload your browser and you should now see a "Login" and "Create" links
613 at the bottom of the page (as mentioned earlier, you can update template
614 files without reloading the development server). Click the first link
615 to return to the login page. This time you I<should> see the "You are
616 already logged in" message.
618 Finally, click the C<You can logout here> link on the C</login> page.
619 You should stay at the login page, but the message should change to "You
620 need to log in to use this application."
623 =head1 USING PASSWORD HASHES
625 In this section we increase the security of our system by converting
626 from cleartext passwords to SHA-1 password hashes that include a
627 random "salt" value to make them extremely difficult to crack with
628 dictionary and "rainbow table" attacks.
630 B<Note:> This section is optional. You can skip it and the rest of the
631 tutorial will function normally.
633 Be aware that even with the techniques shown in this section, the browser
634 still transmits the passwords in cleartext to your application. We are
635 just avoiding the I<storage> of cleartext passwords in the database by
636 using a salted SHA-1 hash. If you are concerned about cleartext passwords
637 between the browser and your application, consider using SSL/TLS, made
638 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
641 =head2 Install DBIx::Class::EncodedColumn
643 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> provides features
644 that can greatly simplify the maintenance of passwords. It's currently
645 not available as a .deb package in the normal Debian repositories, so let's
646 install it directly from CPAN:
648 $ sudo cpan DBIx::Class::EncodedColumn
651 =head2 Re-Run the DBIC::Schema Model Helper to Include DBIx::Class::EncodedColumn
653 Next, we can re-run the model helper to have it include
654 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> in all of the
655 Result Classes it generates for us. Simply use the same command we
656 saw in Chapters 3 and 4, but add C<,EncodedColumn> to the C<components>
659 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
660 create=static components=TimeStamp,EncodedColumn dbi:SQLite:myapp.db
662 If you then open one of the Result Classes, you will see that it
663 includes EncodedColumn in the C<load_components> line. Take a look at
664 C<lib/MyApp/Schema/Result/Users.pm> since that's the main class where we
665 want to use hashed and salted passwords:
667 __PACKAGE__->load_components("InflateColumn::DateTime", "TimeStamp", "EncodedColumn", "Core");
670 =head2 Modify the "password" Column to Use EncodedColumn
672 Open the file C<lib/MyApp/Schema/Result/Users.pm> and enter the following
673 text below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" line but above
676 # Have the 'password' column use a SHA-1 hash and 10-character salt
677 # with hex encoding; Generate the 'check_password" method
678 __PACKAGE__->add_columns(
683 encode_class => 'Digest',
684 encode_args => {salt_length => 10},
685 encode_check_method => 'check_password',
689 This redefines the automatically generated definition for the password
690 fields at the top of the Result Class file to now use EncodedColumn
691 logic (C<encoded_column> is set to 1). C<encode_class> can be set to
692 either C<Digest> to use
693 L<DBIx::Class::EncodedColumn::Digest|DBIx::Class::EncodedColumn::Digest>,
694 or C<Crypt::Eksblowfish::Bcrypt> for
695 L<DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt|DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt>.
696 C<encode_args> is then used to customize the type of Digest you
697 selected. Here we only specified the size of the salt to use, but
698 we could have also modified the hashing algorithm ('SHA-256' is
699 the default) and the format to use ('base64' is the default, but
700 'hex' and 'binary' are other options). To use these, you could
701 change the C<encode_args> to something like:
703 encode_args => {algorithm => 'SHA-1',
708 =head2 Load Hashed Passwords in the Database
710 Next, let's create a quick script to load some hashed and salted passwords
711 into the C<password> column of our C<users> table. Open the file
712 C<set_hashed_passwords.pl> in your editor and enter the following text:
721 my $schema = MyApp::Schema->connect('dbi:SQLite:myapp.db');
723 my @users = $schema->resultset('Users')->all;
725 foreach my $user (@users) {
726 $user->password('mypass');
730 EncodedColumn lets us simple call C<$user->check_password($password)>
731 to see if the user has supplied the correct password, or, as we show
732 above, call C<$user->update($new_password)> to update the hashed
733 password stored for this user.
735 Then run the following command:
737 $ perl -Ilib set_hashed_passwords.pl
739 We had to use the C<-Ilib> arguement to tell perl to look under the
740 C<lib> directory for our C<MyApp::Schema> model.
742 Then dump the users table to verify that it worked:
744 $ sqlite3 myapp.db "select * from users"
745 1|test01|38d3974fa9e9263099f7bc2574284b2f55473a9bM=fwpX2NR8|t01@na.com|Joe|Blow|1
746 2|test02|6ed8586587e53e0d7509b1cfed5df08feadc68cbMJlnPyPt0I|t02@na.com|Jane|Doe|1
747 3|test03|af929a151340c6aed4d54d7e2651795d1ad2e2f7UW8dHoGv9z|t03@na.com|No|Go|0
749 As you can see, the passwords are much harder to steal from the
750 database. Also note that this demonstrates how to use a DBIx::Class
751 model outside of your web application -- a very useful feature in many
755 =head2 Enable Hashed and Salted Passwords
757 Edit C<lib/MyApp.pm> and update it to match the following text (the only change
758 is to the C<password_type> field):
760 # Configure SimpleDB Authentication
761 __PACKAGE__->config->{'Plugin::Authentication'} = {
764 user_model => 'DB::Users',
765 password_type => 'self_check',
769 The use of C<self_check> will cause
770 Catalyst::Plugin::Authentication::Store::DBIC to call the
771 C<check_password> method we enabled on our C<password> columns.
774 =head2 Try Out the Hashed Passwords
776 Press C<Ctrl-C> to kill the previous server instance (if it's still
777 running) and restart it:
779 $ script/myapp_server.pl
781 You should now be able to go to L<http://localhost:3000/books/list> and
782 login as before. When done, click the "logout" link on the login page
783 (or point your browser at L<http://localhost:3000/logout>).
786 =head1 USING THE SESSION FOR FLASH
788 As discussed in the previous chapter of the tutorial, C<flash> allows
789 you to set variables in a way that is very similar to C<stash>, but it
790 will remain set across multiple requests. Once the value is read, it
791 is cleared (unless reset). Although C<flash> has nothing to do with
792 authentication, it does leverage the same session plugins. Now that
793 those plugins are enabled, let's go back and update the "delete and
794 redirect with query parameters" code seen at the end of the L<Basic
795 CRUD|Catalyst::Manual::Tutorial::BasicCRUD> chapter of the tutorial to
796 take advantage of C<flash>.
798 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
799 to match the following (everything after the model search line of code
808 sub delete :Chained('object') :PathPart('delete') :Args(0) {
811 # Use the book object saved by 'object' and delete it along
812 # with related 'book_authors' entries
813 $c->stash->{object}->delete;
815 # Use 'flash' to save information across requests until it's read
816 $c->flash->{status_msg} = "Book deleted";
818 # Redirect the user back to the list page
819 $c->response->redirect($c->uri_for($self->action_for('list')));
822 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
823 flash vs. the C<status_msg> query parameter:
827 [%# Status and error messages %]
828 <span class="message">[% status_msg || c.flash.status_msg %]</span>
829 <span class="error">[% error_msg %]</span>
830 [%# This is where TT will stick all of your template's contents. -%]
832 </div><!-- end content -->
835 Although the sample above only shows the C<content> div, leave the
836 rest of the file intact -- the only change we made to the C<wrapper.tt2>
837 was to add "C<|| c.request.params.status_msg>" to the
838 C<E<lt>span class="message"E<gt>> line.
843 Restart the development server, log in, and then point your browser to
844 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
845 several books. Click the "Return to list" link and delete one of the
846 "Test" books you just added. The C<flash> mechanism should retain our
847 "Book deleted" status message across the redirect.
849 B<NOTE:> While C<flash> will save information across multiple requests,
850 I<it does get cleared the first time it is read>. In general, this is
851 exactly what you want -- the C<flash> message will get displayed on
852 the next screen where it's appropriate, but it won't "keep showing up"
853 after that first time (unless you reset it). Please refer to
854 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
858 =head2 Switch To Flash-To-Stash
860 Although the a use of flash above works well, the
861 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
862 alternative is to use the C<flash_to_stash> feature that automatically
863 copies the content of flash to stash. This makes your controller
864 and template code work regardless of where it was directly access, a
865 forward, or a redirect. To enable C<flash_to_stash>, you can either
866 set the value in C<lib/MyApp.pm> by changing the default
867 C<__PACKAGE__-E<gt>config> setting to something like:
871 session => {flash_to_stash => 1}
874 B<or> add the following to C<myapp.conf>:
880 The C<__PACKAGE__-E<gt>config> option is probably preferable here
881 since it's not something you will want to change at runtime without it
882 possibly breaking some of your code.
884 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
885 to match the following:
887 <span class="message">[% status_msg %]</span>
889 Restart the development server and go to
890 L<http://localhost:3000/books/list> in your browser. Delete another
891 of the "Test" books you added in the previous step. Flash should still
892 maintain the status message across the redirect even though you are no
893 longer explicitly accessing C<c.flash>.
898 Kennedy Clark, C<hkclark@gmail.com>
900 Please report any errors, issues or suggestions to the author. The
901 most recent version of the Catalyst Tutorial can be found at
902 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
904 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
905 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).