3 Catalyst::Manual::Tutorial::05_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::01_Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
36 L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::08_Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::10_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::01_Intro|Catalyst::Manual::Tutorial::01_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 user and role tables, along with a many-to-many join table
88 id INTEGER PRIMARY KEY,
97 id INTEGER PRIMARY KEY,
100 CREATE TABLE user_role (
101 user_id INTEGER REFERENCES user(id) ON DELETE CASCADE ON UPDATE CASCADE,
102 role_id INTEGER REFERENCES role(id) ON DELETE CASCADE ON UPDATE CASCADE,
103 PRIMARY KEY (user_id, role_id)
106 -- Load up some initial test data
108 INSERT INTO user VALUES (1, 'test01', 'mypass', 't01@na.com', 'Joe', 'Blow', 1);
109 INSERT INTO user VALUES (2, 'test02', 'mypass', 't02@na.com', 'Jane', 'Doe', 1);
110 INSERT INTO user VALUES (3, 'test03', 'mypass', 't03@na.com', 'No', 'Go', 0);
111 INSERT INTO role VALUES (1, 'user');
112 INSERT INTO role VALUES (2, 'admin');
113 INSERT INTO user_role VALUES (1, 1);
114 INSERT INTO user_role VALUES (1, 2);
115 INSERT INTO user_role VALUES (2, 1);
116 INSERT INTO user_role 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 on_connect_do="PRAGMA foreign_keys = ON"
132 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
133 exists "/root/dev/MyApp/script/../t"
134 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
135 Schema dump completed.
136 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
138 $ ls lib/MyApp/Schema/Result
139 Author.pm BookAuthor.pm Book.pm Role.pm User.pm UserRole.pm
141 Notice how the helper has added three new table-specific result source
142 files to the C<lib/MyApp/Schema/Result> directory. And, more
143 importantly, even if there were changes to the existing result source
144 files, those changes would have only been written above the C<# DO NOT
145 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-edited
146 enhancements would have been preserved.
148 Speaking of "hand-editted enhancements," we should now add
149 relationship information to the three new result source files. Edit
150 each of these files and add the following information between the C<#
151 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
153 C<lib/MyApp/Schema/Result/User.pm>:
158 # 1) Name of relationship, DBIC will create accessor with this name
159 # 2) Name of has_many() relationship this many_to_many() is shortcut for
160 # 3) Name of belongs_to() relationship in model class of has_many() above
161 # You must already have the has_many() defined to use a many_to_many().
162 __PACKAGE__->many_to_many(roles => 'user_roles', 'role');
165 The code for this update is obviously very similar to the edits we made to the
166 C<Book> and C<Author> classes created in Chapter 3.
168 Note that we do not need to make any change to the
169 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to load all
170 of the Result Class and ResultSet Class files it finds in below the
171 C<lib/MyApp/Schema> directory, so it will automatically pick up our
172 new table information.
175 =head2 Sanity-Check Reload of Development Server
177 We aren't ready to try out the authentication just yet; we only want
178 to do a quick check to be sure our model loads correctly. Press
179 C<Ctrl-C> to kill the previous server instance (if it's still running)
182 $ script/myapp_server.pl
184 Look for the three new model objects in the startup debug output:
187 .-------------------------------------------------------------------+----------.
189 +-------------------------------------------------------------------+----------+
190 | MyApp::Controller::Books | instance |
191 | MyApp::Controller::Root | instance |
192 | MyApp::Model::DB | instance |
193 | MyApp::Model::DB::Author | class |
194 | MyApp::Model::DB::Book | class |
195 | MyApp::Model::DB::BookAuthor | class |
196 | MyApp::Model::DB::Role | class |
197 | MyApp::Model::DB::User | class |
198 | MyApp::Model::DB::UserRole | class |
199 | MyApp::View::TT | instance |
200 '-------------------------------------------------------------------+----------'
203 Again, notice that your "Result Class" classes have been "re-loaded"
204 by Catalyst under C<MyApp::Model>.
207 =head2 Include Authentication and Session Plugins
209 Edit C<lib/MyApp.pm> and update it as follows (everything below
210 C<StackTrace> is new):
223 Session::Store::FastMmap
224 Session::State::Cookie
227 B<Note:> As discussed in MoreCatalystBasics, different versions of
228 C<Catalyst::Devel> have used a variety of methods to load the plugins,
229 but we are going to use the current Catalyst 5.8X practice of putting
230 them on the C<use Catalyst> line.
232 The C<Authentication> plugin supports Authentication while the
233 C<Session> plugins are required to maintain state across multiple HTTP
236 Note that the only required Authentication class is the main one. This
237 is a change that occurred in version 0.09999_01 of the
238 C<Authentication> plugin. You B<do not need> to specify a particular
239 Authentication::Store or Authentication::Credential plugin. Instead,
240 indicate the Store and Credential you want to use in your application
241 configuration (see below).
243 Make sure you include the additional plugins as new dependencies in
244 the Makefile.PL file something like this:
247 'Catalyst::Plugin::Authentication' => '0',
248 'Catalyst::Plugin::Session' => '0',
249 'Catalyst::Plugin::Session::Store::FastMmap' => '0',
250 'Catalyst::Plugin::Session::State::Cookie' => '0',
253 Note that there are several options for
254 L<Session::Store|Catalyst::Plugin::Session::Store>
255 (L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap>
256 is generally a good choice if you are on Unix; try
257 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
258 are on Win32) -- consult
259 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
260 for additional information and options (for example to use a database-
261 backed session store).
264 =head2 Configure Authentication
266 There are a variety of ways to provide configuration information to
267 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>.
269 L<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
270 because it automatically sets a reasonable set of defaults for us. Open
271 C<lib/MyApp.pm> and place the following text above the call to
272 C<__PACKAGE__-E<gt>setup();>:
274 # Configure SimpleDB Authentication
275 __PACKAGE__->config->{'Plugin::Authentication'} = {
278 user_model => 'DB::User',
279 password_type => 'clear',
283 We could have placed this configuration in C<myapp.conf>, but placing
284 it in C<lib/MyApp.pm> is probably a better place since it's not likely
285 something that users of your application will want to change during
286 deployment (or you could use a mixture: leave C<class> and
287 C<user_model> defined in C<lib/MyApp.pm> as we show above, but place
288 C<password_type> in C<myapp.conf> to allow the type of password to be
289 easily modified during deployment). We will stick with putting
290 all of the authentication-related configuration in C<lib/MyApp.pm>
291 for the tutorial, but if you wish to use C<myapp.conf>, just convert
292 to the following code:
294 <Plugin::Authentication>
300 </Plugin::Authentication>
302 B<TIP:> Here is a short script that will dump the contents of
303 C<MyApp->config> to L<Config::General|Config::General> format in
306 $ perl -Ilib -e 'use MyApp; use Config::General;
307 Config::General->new->save_file("myapp.conf", MyApp->config);'
309 B<NOTE:> Because we are using SimpleDB along with a database layout
310 that complies with its default assumptions, we don't need to specify
311 the names of the columns where our username and password information
312 is stored (hence, the "Simple" part of "SimpleDB"). That being said,
313 SimpleDB lets you specify that type of information if you need to.
315 C<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
319 =head2 Add Login and Logout Controllers
321 Use the Catalyst create script to create two stub controller files:
323 $ script/myapp_create.pl controller Login
324 $ script/myapp_create.pl controller Logout
326 You could easily use a single controller here. For example, you could
327 have a C<User> controller with both C<login> and C<logout> actions.
328 Remember, Catalyst is designed to be very flexible, and leaves such
329 matters up to you, the designer and programmer.
331 Then open C<lib/MyApp/Controller/Login.pm>, locate the
332 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
333 are using an older version of Catalyst) that was automatically
334 inserted by the helpers when we created the Login controller above,
335 and update the definition of C<sub index> to match:
343 sub index :Path :Args(0) {
346 # Get the username and password from form
347 my $username = $c->request->params->{username};
348 my $password = $c->request->params->{password};
350 # If the username and password values were found in form
351 if ($username && $password) {
352 # Attempt to log the user in
353 if ($c->authenticate({ username => $username,
354 password => $password } )) {
355 # If successful, then let them use the application
356 $c->response->redirect($c->uri_for(
357 $c->controller('Books')->action_for('list')));
360 # Set an error message
361 $c->stash->{error_msg} = "Bad username or password.";
364 # Set an error message
365 $c->stash->{error_msg} = "Empty username or password.";
368 # If either of above don't work out, send to the login page
369 $c->stash->{template} = 'login.tt2';
372 Be sure to remove the C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Login in Login.');>
373 line of the C<sub index>.
375 This controller fetches the C<username> and C<password> values from the
376 login form and attempts to authenticate the user. If successful, it
377 redirects the user to the book list page. If the login fails, the user
378 will stay at the login page and receive an error message. If the
379 C<username> and C<password> values are not present in the form, the
380 user will be taken to the empty login form.
382 Note that we could have used something like "C<sub default :Path>",
383 however, it is generally recommended (partly for historical reasons,
384 and partly for code clarity) only to use C<default> in
385 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
386 found page for the application.
388 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
389 specifically match the URL C</login>. C<Path> actions (aka, "literal
390 actions") create URI matches relative to the namespace of the
391 controller where they are defined. Although C<Path> supports
392 arguments that allow relative and absolute paths to be defined, here
393 we use an empty C<Path> definition to match on just the name of the
394 controller itself. The method name, C<index>, is arbitrary. We make
395 the match even more specific with the C<:Args(0)> action modifier --
396 this forces the match on I<only> C</login>, not
397 C</login/somethingelse>.
399 Next, update the corresponding method in
400 C<lib/MyApp/Controller/Logout.pm> to match:
408 sub index :Path :Args(0) {
411 # Clear the user's state
414 # Send the user to the starting point
415 $c->response->redirect($c->uri_for('/'));
418 As with the login controller, be sure to delete the
419 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
420 line of the C<sub index>.
423 =head2 Add a Login Form TT Template Page
425 Create a login form by opening C<root/src/login.tt2> and inserting:
427 [% META title = 'Login' %]
430 <form method="post" action="[% c.uri_for('/login') %]">
434 <td><input type="text" name="username" size="40" /></td>
438 <td><input type="password" name="password" size="40" /></td>
441 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
447 =head2 Add Valid User Check
449 We need something that provides enforcement for the authentication
450 mechanism -- a I<global> mechanism that prevents users who have not
451 passed authentication from reaching any pages except the login page.
452 This is generally done via an C<auto> action/method in
453 C<lib/MyApp/Controller/Root.pm>.
455 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
456 the following method:
460 Check if there is a user and, if not, forward to login page
464 # Note that 'auto' runs after 'begin' but before your actions and that
465 # 'auto's "chain" (all from application path to most specific class are run)
466 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
470 # Allow unauthenticated users to reach the login page. This
471 # allows unauthenticated users to reach any action in the Login
472 # controller. To lock it down to a single action, we could use:
473 # if ($c->action eq $c->controller('Login')->action_for('index'))
474 # to only allow unauthenticated access to the 'index' action we
476 if ($c->controller eq $c->controller('Login')) {
480 # If a user doesn't exist, force login
481 if (!$c->user_exists) {
482 # Dump a log message to the development server debug output
483 $c->log->debug('***Root::auto User not found, forwarding to /login');
484 # Redirect the user to the login page
485 $c->response->redirect($c->uri_for('/login'));
486 # Return 0 to cancel 'post-auto' processing and prevent use of application
490 # User found, so return 1 to continue with processing after this 'auto'
495 L<Catalyst::Manual::Tutorial::03_MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
496 every C<auto> method from the application/root controller down to the
497 most specific controller will be called. By placing the
498 authentication enforcement code inside the C<auto> method of
499 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
500 called for I<every> request that is received by the entire
504 =head2 Displaying Content Only to Authenticated Users
506 Let's say you want to provide some information on the login page that
507 changes depending on whether the user has authenticated yet. To do
508 this, open C<root/src/login.tt2> in your editor and add the following
509 lines to the bottom of the file:
514 # This code illustrates how certain parts of the TT
515 # template will only be shown to users who have logged in
517 [% IF c.user_exists %]
518 Please Note: You are already logged in as '[% c.user.username %]'.
519 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
521 You need to log in to use this application.
524 Note that this whole block is a comment because the "#" appears
525 immediate after the "[%" (with no spaces in between). Although it
526 can be a handy way to temporarily "comment out" a whole block of
527 TT code, it's probably a little too subtle for use in "normal"
532 Although most of the code is comments, the middle few lines provide a
533 "you are already logged in" reminder if the user returns to the login
534 page after they have already authenticated. For users who have not yet
535 authenticated, a "You need to log in..." message is displayed (note the
536 use of an IF-THEN-ELSE construct in TT).
539 =head2 Try Out Authentication
541 Press C<Ctrl-C> to kill the previous server instance (if it's still
542 running) and restart it:
544 $ script/myapp_server.pl
546 B<IMPORTANT NOTE:> If you are having issues with authentication on
547 Internet Explorer, be sure to check the system clocks on both your
548 server and client machines. Internet Explorer is very picky about
549 timestamps for cookies. You can quickly sync a Debian system by
550 installing the "ntpdate" package:
552 sudo aptitude -y install ntpdate
554 And then run the following command:
558 Or, depending on your firewall configuration:
560 sudo ntpdate-debian -u
562 Note: NTP can be a little more finicky about firewalls because it uses
563 UDP vs. the more common TCP that you see with most Internet protocols.
564 Worse case, you might have to manually set the time on your development
565 box instead of using NTP.
567 Now trying going to L<http://localhost:3000/books/list> and you should
568 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
569 if necessary (the "You are already logged in" message should I<not>
570 appear -- if it does, click the C<logout> button and try again). Note
571 the C<***Root::auto User not found...> debug message in the
572 development server output. Enter username C<test01> and password
573 C<mypass>, and you should be taken to the Book List page.
575 Open C<root/src/books/list.tt2> and add the following lines to the
576 bottom (below the closing </table> tag):
579 <a href="[% c.uri_for('/login') %]">Login</a>
580 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
583 Reload your browser and you should now see a "Login" and "Create" links
584 at the bottom of the page (as mentioned earlier, you can update template
585 files without reloading the development server). Click the first link
586 to return to the login page. This time you I<should> see the "You are
587 already logged in" message.
589 Finally, click the C<You can logout here> link on the C</login> page.
590 You should stay at the login page, but the message should change to "You
591 need to log in to use this application."
594 =head1 USING PASSWORD HASHES
596 In this section we increase the security of our system by converting
597 from cleartext passwords to SHA-1 password hashes that include a
598 random "salt" value to make them extremely difficult to crack with
599 dictionary and "rainbow table" attacks.
601 B<Note:> This section is optional. You can skip it and the rest of the
602 tutorial will function normally.
604 Be aware that even with the techniques shown in this section, the browser
605 still transmits the passwords in cleartext to your application. We are
606 just avoiding the I<storage> of cleartext passwords in the database by
607 using a salted SHA-1 hash. If you are concerned about cleartext passwords
608 between the browser and your application, consider using SSL/TLS, made
609 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
612 =head2 Re-Run the DBIC::Schema Model Helper to Include DBIx::Class::EncodedColumn
614 Next, we can re-run the model helper to have it include
615 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> in all of the
616 Result Classes it generates for us. Simply use the same command we
617 saw in Chapters 3 and 4, but add C<,EncodedColumn> to the C<components>
620 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
621 create=static components=TimeStamp,EncodedColumn dbi:SQLite:myapp.db \
622 on_connect_do="PRAGMA foreign_keys = ON"
624 If you then open one of the Result Classes, you will see that it
625 includes EncodedColumn in the C<load_components> line. Take a look at
626 C<lib/MyApp/Schema/Result/User.pm> since that's the main class where we
627 want to use hashed and salted passwords:
629 __PACKAGE__->load_components("InflateColumn::DateTime", "TimeStamp", "EncodedColumn", "Core");
632 =head2 Modify the "password" Column to Use EncodedColumn
634 Open the file C<lib/MyApp/Schema/Result/User.pm> and enter the following
635 text below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" line but above
638 # Have the 'password' column use a SHA-1 hash and 10-character salt
639 # with hex encoding; Generate the 'check_password" method
640 __PACKAGE__->add_columns(
645 encode_class => 'Digest',
646 encode_args => {salt_length => 10},
647 encode_check_method => 'check_password',
651 This redefines the automatically generated definition for the password
652 fields at the top of the Result Class file to now use EncodedColumn
653 logic (C<encoded_column> is set to 1). C<encode_class> can be set to
654 either C<Digest> to use
655 L<DBIx::Class::EncodedColumn::Digest|DBIx::Class::EncodedColumn::Digest>,
656 or C<Crypt::Eksblowfish::Bcrypt> for
657 L<DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt|DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt>.
658 C<encode_args> is then used to customize the type of Digest you
659 selected. Here we only specified the size of the salt to use, but
660 we could have also modified the hashing algorithm ('SHA-256' is
661 the default) and the format to use ('base64' is the default, but
662 'hex' and 'binary' are other options). To use these, you could
663 change the C<encode_args> to something like:
665 encode_args => {algorithm => 'SHA-1',
670 =head2 Load Hashed Passwords in the Database
672 Next, let's create a quick script to load some hashed and salted passwords
673 into the C<password> column of our C<users> table. Open the file
674 C<set_hashed_passwords.pl> in your editor and enter the following text:
683 my $schema = MyApp::Schema->connect('dbi:SQLite:myapp.db');
685 my @users = $schema->resultset('User')->all;
687 foreach my $user (@users) {
688 $user->password('mypass');
692 EncodedColumn lets us simple call C<$user->check_password($password)>
693 to see if the user has supplied the correct password, or, as we show
694 above, call C<$user->update($new_password)> to update the hashed
695 password stored for this user.
697 Then run the following command:
699 $ DBIC_TRACE=1 perl -Ilib set_hashed_passwords.pl
701 We had to use the C<-Ilib> argument to tell perl to look under the
702 C<lib> directory for our C<MyApp::Schema> model.
704 The DBIC_TRACE output should show that the update worked:
706 $ DBIC_TRACE=1 perl -Ilib set_hashed_passwords.pl
707 SELECT me.id, me.username, me.password, me.email_address,
708 me.first_name, me.last_name, me.active FROM user me:
709 UPDATE user SET password = ? WHERE ( id = ? ):
710 'oXiyAcGOjowz7ISUhpIm1IrS8AxSZ9r4jNjpX9VnVeQmN6GRtRKTz', '1'
711 UPDATE user SET password = ? WHERE ( id = ? ):
712 'PmyEPrkB8EGwvaF/DvJm7LIfxoZARjv8ygFIR7pc1gEA1OfwHGNzs', '2'
713 UPDATE user SET password = ? WHERE ( id = ? ):
714 'h7CS1Fm9UCs4hjcbu2im0HumaHCJUq4Uriac+SQgdUMUfFSoOrz3c', '3'
716 But we can further confirm our actions by dumping the users table:
718 $ sqlite3 myapp.db "select * from user"
719 1|test01|38d3974fa9e9263099f7bc2574284b2f55473a9bM=fwpX2NR8|t01@na.com|Joe|Blow|1
720 2|test02|6ed8586587e53e0d7509b1cfed5df08feadc68cbMJlnPyPt0I|t02@na.com|Jane|Doe|1
721 3|test03|af929a151340c6aed4d54d7e2651795d1ad2e2f7UW8dHoGv9z|t03@na.com|No|Go|0
723 As you can see, the passwords are much harder to steal from the
724 database (not only are the hashes stored, but every hash is different
725 even though the passwords are the same because of the added "salt"
726 value). Also note that this demonstrates how to use a DBIx::Class
727 model outside of your web application -- a very useful feature in many
731 =head2 Enable Hashed and Salted Passwords
733 Edit C<lib/MyApp.pm> and update it to match the following text (the
734 only change is to the C<password_type> field):
736 # Configure SimpleDB Authentication
737 __PACKAGE__->config->{'Plugin::Authentication'} = {
740 user_model => 'DB::User',
741 password_type => 'self_check',
745 The use of C<self_check> will cause
746 Catalyst::Plugin::Authentication::Store::DBIC to call the
747 C<check_password> method we enabled on our C<password> columns.
750 =head2 Try Out the Hashed Passwords
752 Press C<Ctrl-C> to kill the previous server instance (if it's still
753 running) and restart it:
755 $ script/myapp_server.pl
757 You should now be able to go to L<http://localhost:3000/books/list> and
758 login as before. When done, click the "logout" link on the login page
759 (or point your browser at L<http://localhost:3000/logout>).
762 =head1 USING THE SESSION FOR FLASH
764 As discussed in the previous chapter of the tutorial, C<flash> allows
765 you to set variables in a way that is very similar to C<stash>, but it
766 will remain set across multiple requests. Once the value is read, it
767 is cleared (unless reset). Although C<flash> has nothing to do with
768 authentication, it does leverage the same session plugins. Now that
769 those plugins are enabled, let's go back and update the "delete and
770 redirect with query parameters" code seen at the end of the L<Basic
771 CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD> chapter of the tutorial to
772 take advantage of C<flash>.
774 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
775 to match the following (everything after the model search line of code
784 sub delete :Chained('object') :PathPart('delete') :Args(0) {
787 # Use the book object saved by 'object' and delete it along
788 # with related 'book_authors' entries
789 $c->stash->{object}->delete;
791 # Use 'flash' to save information across requests until it's read
792 $c->flash->{status_msg} = "Book deleted";
794 # Redirect the user back to the list page
795 $c->response->redirect($c->uri_for($self->action_for('list')));
798 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
799 flash vs. the C<status_msg> query parameter:
803 [%# Status and error messages %]
804 <span class="message">[% status_msg || c.flash.status_msg %]</span>
805 <span class="error">[% error_msg %]</span>
806 [%# This is where TT will stick all of your template's contents. -%]
808 </div><!-- end content -->
811 Although the sample above only shows the C<content> div, leave the
812 rest of the file intact -- the only change we made to replace
813 "|| c.request.params.status_msg" with "c.flash.status_msg" in the
814 C<< <span class="message"> >> line.
819 Restart the development server, log in, and then point your browser to
820 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
821 several books. Click the "Return to list" link and delete one of the
822 "Test" books you just added. The C<flash> mechanism should retain our
823 "Book deleted" status message across the redirect.
825 B<NOTE:> While C<flash> will save information across multiple requests,
826 I<it does get cleared the first time it is read>. In general, this is
827 exactly what you want -- the C<flash> message will get displayed on
828 the next screen where it's appropriate, but it won't "keep showing up"
829 after that first time (unless you reset it). Please refer to
830 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
834 =head2 Switch To Flash-To-Stash
836 Although the a use of flash above works well, the
837 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
838 alternative is to use the C<flash_to_stash> feature that automatically
839 copies the content of flash to stash. This makes your controller
840 and template code work regardless of where it was directly access, a
841 forward, or a redirect. To enable C<flash_to_stash>, you can either
842 set the value in C<lib/MyApp.pm> by changing the default
843 C<__PACKAGE__-E<gt>config> setting to something like:
847 session => {flash_to_stash => 1},
850 B<or> add the following to C<myapp.conf>:
856 The C<__PACKAGE__-E<gt>config> option is probably preferable here
857 since it's not something you will want to change at runtime without it
858 possibly breaking some of your code.
860 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
861 to match the following:
863 <span class="message">[% status_msg %]</span>
865 Restart the development server and go to
866 L<http://localhost:3000/books/list> in your browser. Delete another
867 of the "Test" books you added in the previous step. Flash should still
868 maintain the status message across the redirect even though you are no
869 longer explicitly accessing C<c.flash>.
874 Kennedy Clark, C<hkclark@gmail.com>
876 Please report any errors, issues or suggestions to the author. The
877 most recent version of the Catalyst Tutorial can be found at
878 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
880 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
881 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).