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:
84 PRAGMA foreign_keys = ON;
86 -- Add user and role tables, along with a many-to-many join table
89 id INTEGER PRIMARY KEY,
98 id INTEGER PRIMARY KEY,
101 CREATE TABLE user_role (
102 user_id INTEGER REFERENCES user(id) ON DELETE CASCADE ON UPDATE CASCADE,
103 role_id INTEGER REFERENCES role(id) ON DELETE CASCADE ON UPDATE CASCADE,
104 PRIMARY KEY (user_id, role_id)
107 -- Load up some initial test data
109 INSERT INTO user VALUES (1, 'test01', 'mypass', 't01@na.com', 'Joe', 'Blow', 1);
110 INSERT INTO user VALUES (2, 'test02', 'mypass', 't02@na.com', 'Jane', 'Doe', 1);
111 INSERT INTO user VALUES (3, 'test03', 'mypass', 't03@na.com', 'No', 'Go', 0);
112 INSERT INTO role VALUES (1, 'user');
113 INSERT INTO role VALUES (2, 'admin');
114 INSERT INTO user_role VALUES (1, 1);
115 INSERT INTO user_role VALUES (1, 2);
116 INSERT INTO user_role VALUES (2, 1);
117 INSERT INTO user_role VALUES (3, 1);
119 Then load this into the C<myapp.db> database with the following command:
121 $ sqlite3 myapp.db < myapp02.sql
124 =head2 Add User and Role Information to DBIC Schema
126 Although we could manually edit the DBIC schema information to include
127 the new tables added in the previous step, let's use the C<create=static>
128 option on the DBIC model helper to do most of the work for us:
130 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
131 create=static components=TimeStamp dbi:SQLite:myapp.db \
132 on_connect_do="PRAGMA foreign_keys = ON"
133 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
134 exists "/root/dev/MyApp/script/../t"
135 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
136 Schema dump completed.
137 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
139 $ ls lib/MyApp/Schema/Result
140 Author.pm BookAuthor.pm Book.pm Role.pm User.pm UserRole.pm
142 Notice how the helper has added three new table-specific result source
143 files to the C<lib/MyApp/Schema/Result> directory. And, more
144 importantly, even if there were changes to the existing result source
145 files, those changes would have only been written above the C<# DO NOT
146 MODIFY THIS OR ANYTHING ABOVE!> comment and your hand-edited
147 enhancements would have been preserved.
149 Speaking of "hand-editted enhancements," we should now add
150 relationship information to the three new result source files. Edit
151 each of these files and add the following information between the C<#
152 DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment and the closing C<1;>:
154 C<lib/MyApp/Schema/Result/User.pm>:
159 # 1) Name of relationship, DBIC will create accessor with this name
160 # 2) Name of has_many() relationship this many_to_many() is shortcut for
161 # 3) Name of belongs_to() relationship in model class of has_many() above
162 # You must already have the has_many() defined to use a many_to_many().
163 __PACKAGE__->many_to_many(roles => 'user_roles', 'role');
166 The code for this update is obviously very similar to the edits we made to the
167 C<Book> and C<Author> classes created in Chapter 3.
169 Note that we do not need to make any change to the
170 C<lib/MyApp/Schema.pm> schema file. It simply tells DBIC to load all
171 of the Result Class and ResultSet Class files it finds in below the
172 C<lib/MyApp/Schema> directory, so it will automatically pick up our
173 new table information.
176 =head2 Sanity-Check Reload of Development Server
178 We aren't ready to try out the authentication just yet; we only want
179 to do a quick check to be sure our model loads correctly. Press
180 C<Ctrl-C> to kill the previous server instance (if it's still running)
183 $ script/myapp_server.pl
185 Look for the three new model objects in the startup debug output:
188 .-------------------------------------------------------------------+----------.
190 +-------------------------------------------------------------------+----------+
191 | MyApp::Controller::Books | instance |
192 | MyApp::Controller::Root | instance |
193 | MyApp::Model::DB | instance |
194 | MyApp::Model::DB::Author | class |
195 | MyApp::Model::DB::Book | class |
196 | MyApp::Model::DB::BookAuthor | class |
197 | MyApp::Model::DB::Role | class |
198 | MyApp::Model::DB::User | class |
199 | MyApp::Model::DB::UserRole | class |
200 | MyApp::View::TT | instance |
201 '-------------------------------------------------------------------+----------'
204 Again, notice that your "Result Class" classes have been "re-loaded"
205 by Catalyst under C<MyApp::Model>.
208 =head2 Include Authentication and Session Plugins
210 Edit C<lib/MyApp.pm> and update it as follows (everything below
211 C<StackTrace> is new):
224 Session::Store::FastMmap
225 Session::State::Cookie
228 B<Note:> As discussed in MoreCatalystBasics, different versions of
229 C<Catalyst::Devel> have used a variety of methods to load the plugins,
230 but we are going to use the current Catalyst 5.8X practice of putting
231 them on the C<use Catalyst> line.
233 The C<Authentication> plugin supports Authentication while the
234 C<Session> plugins are required to maintain state across multiple HTTP
237 Note that the only required Authentication class is the main one. This
238 is a change that occurred in version 0.09999_01 of the
239 C<Authentication> plugin. You B<do not need> to specify a particular
240 Authentication::Store or Authentication::Credential plugin. Instead,
241 indicate the Store and Credential you want to use in your application
242 configuration (see below).
244 Make sure you include the additional plugins as new dependencies in
245 the Makefile.PL file something like this:
247 requires 'Catalyst::Plugin::Authentication';
248 requires 'Catalyst::Plugin::Session';
249 requires 'Catalyst::Plugin::Session::Store::FastMmap';
250 requires 'Catalyst::Plugin::Session::State::Cookie';
252 Note that there are several options for
253 L<Session::Store|Catalyst::Plugin::Session::Store>
255 (L<Session::Store::Memcached|Catalyst::Plugin::Session::Store::Memcached> or
256 L<Session::Store::FastMmap|Catalyst::Plugin::Session::Store::FastMmap> is
257 generally a good choice if you are on Unix; try
258 L<Session::Store::File|Catalyst::Plugin::Session::Store::File> if you
259 are on Win32) -- consult
260 L<Session::Store|Catalyst::Plugin::Session::Store> and its subclasses
261 for additional information and options (for example to use a database-
262 backed session store).
265 =head2 Configure Authentication
267 There are a variety of ways to provide configuration information to
268 L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>.
270 L<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
271 because it automatically sets a reasonable set of defaults for us. Open
272 C<lib/MyApp.pm> and place the following text above the call to
273 C<__PACKAGE__-E<gt>setup();>:
275 # Configure SimpleDB Authentication
276 __PACKAGE__->config->{'Plugin::Authentication'} = {
279 user_model => 'DB::User',
280 password_type => 'clear',
284 We could have placed this configuration in C<myapp.conf>, but placing
285 it in C<lib/MyApp.pm> is probably a better place since it's not likely
286 something that users of your application will want to change during
287 deployment (or you could use a mixture: leave C<class> and
288 C<user_model> defined in C<lib/MyApp.pm> as we show above, but place
289 C<password_type> in C<myapp.conf> to allow the type of password to be
290 easily modified during deployment). We will stick with putting
291 all of the authentication-related configuration in C<lib/MyApp.pm>
292 for the tutorial, but if you wish to use C<myapp.conf>, just convert
293 to the following code:
295 <Plugin::Authentication>
301 </Plugin::Authentication>
303 B<TIP:> Here is a short script that will dump the contents of
304 C<MyApp->config> to L<Config::General|Config::General> format in
307 $ perl -Ilib -e 'use MyApp; use Config::General;
308 Config::General->new->save_file("myapp.conf", MyApp->config);'
310 B<NOTE:> Because we are using SimpleDB along with a database layout
311 that complies with its default assumptions, we don't need to specify
312 the names of the columns where our username and password information
313 is stored (hence, the "Simple" part of "SimpleDB"). That being said,
314 SimpleDB lets you specify that type of information if you need to.
316 C<Catalyst::Authentication::Realm::SimpleDB|Catalyst::Authentication::Realm::SimpleDB>
320 =head2 Add Login and Logout Controllers
322 Use the Catalyst create script to create two stub controller files:
324 $ script/myapp_create.pl controller Login
325 $ script/myapp_create.pl controller Logout
327 You could easily use a single controller here. For example, you could
328 have a C<User> controller with both C<login> and C<logout> actions.
329 Remember, Catalyst is designed to be very flexible, and leaves such
330 matters up to you, the designer and programmer.
332 Then open C<lib/MyApp/Controller/Login.pm>, locate the
333 C<sub index :Path :Args(0)> method (or C<sub index : Private> if you
334 are using an older version of Catalyst) that was automatically
335 inserted by the helpers when we created the Login controller above,
336 and update the definition of C<sub index> to match:
344 sub index :Path :Args(0) {
347 # Get the username and password from form
348 my $username = $c->request->params->{username};
349 my $password = $c->request->params->{password};
351 # If the username and password values were found in form
352 if ($username && $password) {
353 # Attempt to log the user in
354 if ($c->authenticate({ username => $username,
355 password => $password } )) {
356 # If successful, then let them use the application
357 $c->response->redirect($c->uri_for(
358 $c->controller('Books')->action_for('list')));
361 # Set an error message
362 $c->stash->{error_msg} = "Bad username or password.";
365 # Set an error message
366 $c->stash->{error_msg} = "Empty username or password.";
369 # If either of above don't work out, send to the login page
370 $c->stash->{template} = 'login.tt2';
373 Be sure to remove the C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Login in Login.');>
374 line of the C<sub index>.
376 This controller fetches the C<username> and C<password> values from the
377 login form and attempts to authenticate the user. If successful, it
378 redirects the user to the book list page. If the login fails, the user
379 will stay at the login page and receive an error message. If the
380 C<username> and C<password> values are not present in the form, the
381 user will be taken to the empty login form.
383 Note that we could have used something like "C<sub default :Path>",
384 however, it is generally recommended (partly for historical reasons,
385 and partly for code clarity) only to use C<default> in
386 C<MyApp::Controller::Root>, and then mainly to generate the 404 not
387 found page for the application.
389 Instead, we are using "C<sub somename :Path :Args(0) {...}>" here to
390 specifically match the URL C</login>. C<Path> actions (aka, "literal
391 actions") create URI matches relative to the namespace of the
392 controller where they are defined. Although C<Path> supports
393 arguments that allow relative and absolute paths to be defined, here
394 we use an empty C<Path> definition to match on just the name of the
395 controller itself. The method name, C<index>, is arbitrary. We make
396 the match even more specific with the C<:Args(0)> action modifier --
397 this forces the match on I<only> C</login>, not
398 C</login/somethingelse>.
400 Next, update the corresponding method in
401 C<lib/MyApp/Controller/Logout.pm> to match:
409 sub index :Path :Args(0) {
412 # Clear the user's state
415 # Send the user to the starting point
416 $c->response->redirect($c->uri_for('/'));
419 As with the login controller, be sure to delete the
420 C<$c-E<gt>response-E<gt>body('Matched MyApp::Controller::Logout in Logout.');>
421 line of the C<sub index>.
424 =head2 Add a Login Form TT Template Page
426 Create a login form by opening C<root/src/login.tt2> and inserting:
428 [% META title = 'Login' %]
431 <form method="post" action="[% c.uri_for('/login') %]">
435 <td><input type="text" name="username" size="40" /></td>
439 <td><input type="password" name="password" size="40" /></td>
442 <td colspan="2"><input type="submit" name="submit" value="Submit" /></td>
448 =head2 Add Valid User Check
450 We need something that provides enforcement for the authentication
451 mechanism -- a I<global> mechanism that prevents users who have not
452 passed authentication from reaching any pages except the login page.
453 This is generally done via an C<auto> action/method in
454 C<lib/MyApp/Controller/Root.pm>.
456 Edit the existing C<lib/MyApp/Controller/Root.pm> class file and insert
457 the following method:
461 Check if there is a user and, if not, forward to login page
465 # Note that 'auto' runs after 'begin' but before your actions and that
466 # 'auto's "chain" (all from application path to most specific class are run)
467 # See the 'Actions' section of 'Catalyst::Manual::Intro' for more info.
471 # Allow unauthenticated users to reach the login page. This
472 # allows unauthenticated users to reach any action in the Login
473 # controller. To lock it down to a single action, we could use:
474 # if ($c->action eq $c->controller('Login')->action_for('index'))
475 # to only allow unauthenticated access to the 'index' action we
477 if ($c->controller eq $c->controller('Login')) {
481 # If a user doesn't exist, force login
482 if (!$c->user_exists) {
483 # Dump a log message to the development server debug output
484 $c->log->debug('***Root::auto User not found, forwarding to /login');
485 # Redirect the user to the login page
486 $c->response->redirect($c->uri_for('/login'));
487 # Return 0 to cancel 'post-auto' processing and prevent use of application
491 # User found, so return 1 to continue with processing after this 'auto'
496 L<Catalyst::Manual::Tutorial::03_MoreCatalystBasics/CREATE A CATALYST CONTROLLER>,
497 every C<auto> method from the application/root controller down to the
498 most specific controller will be called. By placing the
499 authentication enforcement code inside the C<auto> method of
500 C<lib/MyApp/Controller/Root.pm> (or C<lib/MyApp.pm>), it will be
501 called for I<every> request that is received by the entire
505 =head2 Displaying Content Only to Authenticated Users
507 Let's say you want to provide some information on the login page that
508 changes depending on whether the user has authenticated yet. To do
509 this, open C<root/src/login.tt2> in your editor and add the following
510 lines to the bottom of the file:
515 # This code illustrates how certain parts of the TT
516 # template will only be shown to users who have logged in
518 [% IF c.user_exists %]
519 Please Note: You are already logged in as '[% c.user.username %]'.
520 You can <a href="[% c.uri_for('/logout') %]">logout</a> here.
522 You need to log in to use this application.
525 Note that this whole block is a comment because the "#" appears
526 immediate after the "[%" (with no spaces in between). Although it
527 can be a handy way to temporarily "comment out" a whole block of
528 TT code, it's probably a little too subtle for use in "normal"
533 Although most of the code is comments, the middle few lines provide a
534 "you are already logged in" reminder if the user returns to the login
535 page after they have already authenticated. For users who have not yet
536 authenticated, a "You need to log in..." message is displayed (note the
537 use of an IF-THEN-ELSE construct in TT).
540 =head2 Try Out Authentication
542 Press C<Ctrl-C> to kill the previous server instance (if it's still
543 running) and restart it:
545 $ script/myapp_server.pl
547 B<IMPORTANT NOTE:> If you are having issues with authentication on
548 Internet Explorer, be sure to check the system clocks on both your
549 server and client machines. Internet Explorer is very picky about
550 timestamps for cookies. You can quickly sync a Debian system by
551 installing the "ntpdate" package:
553 sudo aptitude -y install ntpdate
555 And then run the following command:
559 Or, depending on your firewall configuration:
561 sudo ntpdate-debian -u
563 Note: NTP can be a little more finicky about firewalls because it uses
564 UDP vs. the more common TCP that you see with most Internet protocols.
565 Worse case, you might have to manually set the time on your development
566 box instead of using NTP.
568 Now trying going to L<http://localhost:3000/books/list> and you should
569 be redirected to the login page, hitting Shift+Reload or Ctrl+Reload
570 if necessary (the "You are already logged in" message should I<not>
571 appear -- if it does, click the C<logout> button and try again). Note
572 the C<***Root::auto User not found...> debug message in the
573 development server output. Enter username C<test01> and password
574 C<mypass>, and you should be taken to the Book List page.
576 Open C<root/src/books/list.tt2> and add the following lines to the
577 bottom (below the closing </table> tag):
580 <a href="[% c.uri_for('/login') %]">Login</a>
581 <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Create</a>
584 Reload your browser and you should now see a "Login" and "Create" links
585 at the bottom of the page (as mentioned earlier, you can update template
586 files without reloading the development server). Click the first link
587 to return to the login page. This time you I<should> see the "You are
588 already logged in" message.
590 Finally, click the C<You can logout here> link on the C</login> page.
591 You should stay at the login page, but the message should change to "You
592 need to log in to use this application."
595 =head1 USING PASSWORD HASHES
597 In this section we increase the security of our system by converting
598 from cleartext passwords to SHA-1 password hashes that include a
599 random "salt" value to make them extremely difficult to crack with
600 dictionary and "rainbow table" attacks.
602 B<Note:> This section is optional. You can skip it and the rest of the
603 tutorial will function normally.
605 Be aware that even with the techniques shown in this section, the browser
606 still transmits the passwords in cleartext to your application. We are
607 just avoiding the I<storage> of cleartext passwords in the database by
608 using a salted SHA-1 hash. If you are concerned about cleartext passwords
609 between the browser and your application, consider using SSL/TLS, made
610 easy with the Catalyst plugin Catalyst::Plugin:RequireSSL.
613 =head2 Re-Run the DBIC::Schema Model Helper to Include DBIx::Class::EncodedColumn
615 Next, we can re-run the model helper to have it include
616 L<DBIx::Class::EncodedColumn|DBIx::Class::EncodedColumn> in all of the
617 Result Classes it generates for us. Simply use the same command we
618 saw in Chapters 3 and 4, but add C<,EncodedColumn> to the C<components>
621 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
622 create=static components=TimeStamp,EncodedColumn dbi:SQLite:myapp.db \
623 on_connect_do="PRAGMA foreign_keys = ON"
625 If you then open one of the Result Classes, you will see that it
626 includes EncodedColumn in the C<load_components> line. Take a look at
627 C<lib/MyApp/Schema/Result/User.pm> since that's the main class where we
628 want to use hashed and salted passwords:
630 __PACKAGE__->load_components("InflateColumn::DateTime", "TimeStamp", "EncodedColumn");
633 =head2 Modify the "password" Column to Use EncodedColumn
635 Open the file C<lib/MyApp/Schema/Result/User.pm> and enter the following
636 text below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" line but above
639 # Have the 'password' column use a SHA-1 hash and 10-character salt
640 # with hex encoding; Generate the 'check_password" method
641 __PACKAGE__->add_columns(
646 encode_class => 'Digest',
647 encode_args => {salt_length => 10},
648 encode_check_method => 'check_password',
652 This redefines the automatically generated definition for the password
653 fields at the top of the Result Class file to now use EncodedColumn
654 logic (C<encoded_column> is set to 1). C<encode_class> can be set to
655 either C<Digest> to use
656 L<DBIx::Class::EncodedColumn::Digest|DBIx::Class::EncodedColumn::Digest>,
657 or C<Crypt::Eksblowfish::Bcrypt> for
658 L<DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt|DBIx::Class::EncodedColumn::Crypt::Eksblowfish::Bcrypt>.
659 C<encode_args> is then used to customize the type of Digest you
660 selected. Here we only specified the size of the salt to use, but
661 we could have also modified the hashing algorithm ('SHA-256' is
662 the default) and the format to use ('base64' is the default, but
663 'hex' and 'binary' are other options). To use these, you could
664 change the C<encode_args> to something like:
666 encode_args => {algorithm => 'SHA-1',
671 =head2 Load Hashed Passwords in the Database
673 Next, let's create a quick script to load some hashed and salted passwords
674 into the C<password> column of our C<users> table. Open the file
675 C<set_hashed_passwords.pl> in your editor and enter the following text:
684 my $schema = MyApp::Schema->connect('dbi:SQLite:myapp.db');
686 my @users = $schema->resultset('User')->all;
688 foreach my $user (@users) {
689 $user->password('mypass');
693 EncodedColumn lets us simple call C<$user->check_password($password)>
694 to see if the user has supplied the correct password, or, as we show
695 above, call C<$user->update($new_password)> to update the hashed
696 password stored for this user.
698 Then run the following command:
700 $ DBIC_TRACE=1 perl -Ilib set_hashed_passwords.pl
702 We had to use the C<-Ilib> argument to tell perl to look under the
703 C<lib> directory for our C<MyApp::Schema> model.
705 The DBIC_TRACE output should show that the update worked:
707 $ DBIC_TRACE=1 perl -Ilib set_hashed_passwords.pl
708 SELECT me.id, me.username, me.password, me.email_address,
709 me.first_name, me.last_name, me.active FROM user me:
710 UPDATE user SET password = ? WHERE ( id = ? ):
711 'oXiyAcGOjowz7ISUhpIm1IrS8AxSZ9r4jNjpX9VnVeQmN6GRtRKTz', '1'
712 UPDATE user SET password = ? WHERE ( id = ? ):
713 'PmyEPrkB8EGwvaF/DvJm7LIfxoZARjv8ygFIR7pc1gEA1OfwHGNzs', '2'
714 UPDATE user SET password = ? WHERE ( id = ? ):
715 'h7CS1Fm9UCs4hjcbu2im0HumaHCJUq4Uriac+SQgdUMUfFSoOrz3c', '3'
717 But we can further confirm our actions by dumping the users table:
719 $ sqlite3 myapp.db "select * from user"
720 1|test01|38d3974fa9e9263099f7bc2574284b2f55473a9bM=fwpX2NR8|t01@na.com|Joe|Blow|1
721 2|test02|6ed8586587e53e0d7509b1cfed5df08feadc68cbMJlnPyPt0I|t02@na.com|Jane|Doe|1
722 3|test03|af929a151340c6aed4d54d7e2651795d1ad2e2f7UW8dHoGv9z|t03@na.com|No|Go|0
724 As you can see, the passwords are much harder to steal from the
725 database (not only are the hashes stored, but every hash is different
726 even though the passwords are the same because of the added "salt"
727 value). Also note that this demonstrates how to use a DBIx::Class
728 model outside of your web application -- a very useful feature in many
732 =head2 Enable Hashed and Salted Passwords
734 Edit C<lib/MyApp.pm> and update it to match the following text (the
735 only change is to the C<password_type> field):
737 # Configure SimpleDB Authentication
738 __PACKAGE__->config->{'Plugin::Authentication'} = {
741 user_model => 'DB::User',
742 password_type => 'self_check',
746 The use of C<self_check> will cause
747 Catalyst::Plugin::Authentication::Store::DBIC to call the
748 C<check_password> method we enabled on our C<password> columns.
751 =head2 Try Out the Hashed Passwords
753 Press C<Ctrl-C> to kill the previous server instance (if it's still
754 running) and restart it:
756 $ script/myapp_server.pl
758 You should now be able to go to L<http://localhost:3000/books/list> and
759 login as before. When done, click the "logout" link on the login page
760 (or point your browser at L<http://localhost:3000/logout>).
763 =head1 USING THE SESSION FOR FLASH
765 As discussed in the previous chapter of the tutorial, C<flash> allows
766 you to set variables in a way that is very similar to C<stash>, but it
767 will remain set across multiple requests. Once the value is read, it
768 is cleared (unless reset). Although C<flash> has nothing to do with
769 authentication, it does leverage the same session plugins. Now that
770 those plugins are enabled, let's go back and update the "delete and
771 redirect with query parameters" code seen at the end of the L<Basic
772 CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD> chapter of the tutorial to
773 take advantage of C<flash>.
775 First, open C<lib/MyApp/Controller/Books.pm> and modify C<sub delete>
776 to match the following (everything after the model search line of code
785 sub delete :Chained('object') :PathPart('delete') :Args(0) {
788 # Use the book object saved by 'object' and delete it along
789 # with related 'book_authors' entries
790 $c->stash->{object}->delete;
792 # Use 'flash' to save information across requests until it's read
793 $c->flash->{status_msg} = "Book deleted";
795 # Redirect the user back to the list page
796 $c->response->redirect($c->uri_for($self->action_for('list')));
799 Next, open C<root/src/wrapper.tt2> and update the TT code to pull from
800 flash vs. the C<status_msg> query parameter:
804 [%# Status and error messages %]
805 <span class="message">[% status_msg || c.flash.status_msg %]</span>
806 <span class="error">[% error_msg %]</span>
807 [%# This is where TT will stick all of your template's contents. -%]
809 </div><!-- end content -->
812 Although the sample above only shows the C<content> div, leave the
813 rest of the file intact -- the only change we made to replace
814 "|| c.request.params.status_msg" with "c.flash.status_msg" in the
815 C<< <span class="message"> >> line.
820 Restart the development server, log in, and then point your browser to
821 L<http://localhost:3000/books/url_create/Test/1/4> to create an extra
822 several books. Click the "Return to list" link and delete one of the
823 "Test" books you just added. The C<flash> mechanism should retain our
824 "Book deleted" status message across the redirect.
826 B<NOTE:> While C<flash> will save information across multiple requests,
827 I<it does get cleared the first time it is read>. In general, this is
828 exactly what you want -- the C<flash> message will get displayed on
829 the next screen where it's appropriate, but it won't "keep showing up"
830 after that first time (unless you reset it). Please refer to
831 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> for additional
835 =head2 Switch To Flash-To-Stash
837 Although the a use of flash above works well, the
838 C<status_msg || c.flash.status_msg> statement is a little ugly. A nice
839 alternative is to use the C<flash_to_stash> feature that automatically
840 copies the content of flash to stash. This makes your controller
841 and template code work regardless of where it was directly access, a
842 forward, or a redirect. To enable C<flash_to_stash>, you can either
843 set the value in C<lib/MyApp.pm> by changing the default
844 C<__PACKAGE__-E<gt>config> setting to something like:
848 session => { flash_to_stash => 1 },
851 B<or> add the following to C<myapp.conf>:
857 The C<__PACKAGE__-E<gt>config> option is probably preferable here
858 since it's not something you will want to change at runtime without it
859 possibly breaking some of your code.
861 Then edit C<root/src/wrapper.tt2> and change the C<status_msg> line
862 to match the following:
864 <span class="message">[% status_msg %]</span>
866 Restart the development server and go to
867 L<http://localhost:3000/books/list> in your browser. Delete another
868 of the "Test" books you added in the previous step. Flash should still
869 maintain the status message across the redirect even though you are no
870 longer explicitly accessing C<c.flash>.
875 Kennedy Clark, C<hkclark@gmail.com>
877 Please report any errors, issues or suggestions to the author. The
878 most recent version of the Catalyst Tutorial can be found at
879 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
881 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
882 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).