[catagits/Catalyst-Runtime.git] / lib / Catalyst / Manual / Tutorial / Authorization.pod

=head1 NAME

Catalyst::Manual::Tutorial::Authorization - Catalyst Tutorial  Part 5: Authorization


=head1 OVERVIEW

This is B<Part 5 of 9> for the Catalyst tutorial.

L<Totorial Overview|Catalyst::Manual::Tutorial>

=over 4

=item 1

L<Introduction|Catalyst::Manual::Tutorial::Intro>

=item 2

L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>

=item 3

L<Basic CRUD|Catalyst::Manual::Tutorial03_BasicCRUD>

=item 4

L<Authentication|Catalyst::Manual::Tutorial::Authentication>

=item 5

B<Authorization>

=item 6

L<Debugging|Catalyst::Manual::Tutorial::Debugging>

=item 7

L<Testing|Catalyst::Manual::Tutorial::Testing>

=item 8

L<AdvancedCRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>

=item 9

L<Appendicies|Catalyst::Manual::Tutorial::Appendicies>

=back


=head1 DESCRIPTION

This part of the tutorial adds role-based authorization to the existing authentication implemented in Part 4.  It provides simple examples of how to use roles in both TT templates and controller actions.  The first half looks at manually configured authorization.  The second half looks at how the ACL authorization plugin can simplify your code.

B<TIP>: Note that all of the code for this part of the tutorial can be pulled from the Catalyst Subversion repository in one step with the following command:

    svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial@###
    IMPORTANT: Does not work yet.  Will be completed for final version.


=head1 BASIC AUTHORIZATION

In this section you learn how to manually configure authorization.


=head2 Update Plugins to Include Support Authorization

Edit C<lib/MyApp.pm> and add C<Authorization::Roles> to the list:

    use Catalyst qw/
            -Debug
            ConfigLoader
            Static::Simple
            
            Dumper
            StackTrace
            DefaultEnd
            
            Authentication
            Authentication::Store::DBIC
            Authentication::Credential::Password
            Authorization::Roles
            
            Session
            Session::Store::FastMmap
            Session::State::Cookie
            /;


=head2 Add Config Information for Authorization

Edit C<myapp.yml> and update it to match (everything from the "authorization:" line down is new):

    ---
    name: MyApp
    authentication:
        dbic:
            # Note this first definition would be the same as setting
            # __PACKAGE__->config->{authentication}->{dbic}->{user_class} = 'MyAppDB::User'
            # in lib/MyApp.pm (IOW, each hash key becomes a "name:" in the YAML file).
            #
            # This is the model object created by Catalyst::Model::DBIC from your
            # schema (you created 'MyAppDB::User' but as the Catalyst startup
            # debug messages show, it was loaded as 'MyApp::Model::MyAppDB::User').
            # NOTE: Omit 'MyAppDB::Model' to avoid a component lookup issue in Catalyst 5.66
            user_class: MyAppDB::User
            # This is the name of the field in your 'users' table that contains the user's name
            user_field: username
            # This is the name of the field in your 'users' table that contains the password
            password_field: password
            # Other options can go here for hashed passwords
            # Enabled hashed passwords
            password_type: hashed
            # Use the SHA-1 hashing algorithm
            password_hash_type: SHA-1
    authorization:
        dbic:
            # This is the model object created by Catalyst::Model::DBIC from your
            # schema (you created 'MyAppDB::Role' but as the Catalyst startup
            # debug messages show, it was loaded as 'MyApp::Model::MyAppDB::Role').
            # NOTE: Omit 'MyAppDB::Model' to avoid a component lookup issue in Catalyst 5.66
            role_class: MyAppDB::Role
            # The name of the field in the 'roles' table that contains the role name
            role_field: role
            # The name of the accessor used to map a user to a role
            # See the has_many() in MyAppDB/User.pm
            role_rel: map_user_role
            # The name of the field in the user_role table that references the user
            user_role_user_field: user_id


=head2 Add Role-Specific Logic to the "Book List" Template

Open C<root/src/books/list.tt2> in your editor and add the following lines to the bottom of the file:

    <p>Hello [% Catalyst.user.username %], you have the following roles:</p>
    
    <ul>
      [% # Dump list of roles -%]
      [% FOR role = Catalyst.user.roles %]<li>[% role %]</li>[% END %]
    </ul>
    
    <p>
    [% # Add some simple role-specific logic to template %]
    [% # Use $c->check_user_roles() to check authz -%]
    [% IF Catalyst.check_user_roles('user') %]
      [% # Give normal users a link for 'logout' %]
      <a href="[% Catalyst.uri_for('/logout') %]">Logout</a>
    [% END %]
    
    [% # Can also use $c->user->check_roles() to check authz -%]
    [% IF Catalyst.check_user_roles('admin') %]
      [% # Give admin users a link for 'create' %]
      <a href="[% Catalyst.uri_for('form_create') %]">Create</a>
    [% END %]
    </p>

This code displays a different combination of links depending on the roles assigned to the user..


=head2 Limit C<Books::add> to C<admin> Users

C<IF> statements in TT templates simply control the output that is sent to the user's browser; it provides no real enforcement (if users know or guess the appropriate URLs, they are still perfectly free to hit any action within your application).  We need to enhance the controller logic to wrap restricted actions with role validation logic.  

For example, we might want to restrict the "formless create" action to admin-level users by editing C<lib/MyApp/Controller/Books.pm> and updating C<url_create> to match the following code:

    =head2 url_create

    Create a book with the supplied title, and rating 
    with manual authorization
    
    =cut
    
    sub url_create : Local {
        # In addition to self & context, get the title, rating & author_id args
        # from the URL.  Note that Catalyst automatically puts extra information
        # after the "/<controller_name>/<action_name/" into @_
        my ($self, $c, $title, $rating, $author_id) = @_;
    
        # Check the user's roles
        if ($c->check_user_roles('admin')) {
            # Call create() on the book model object. Pass the table 
            # columns/field values we want to set as hash values
            my $book = $c->model('MyAppDB::Book')->create({
                    title   => $title,
                    rating  => $rating
                });
            
            # Add a record to the join table for this book, mapping to 
            # appropriate author
            $book->add_to_book_authors({author_id => $author_id});
            # Note: Above is a shortcut for this:
            # $book->create_related('book_authors', {author_id => $author_id});
            
            # Assign the Book object to the stash for display in the view
            $c->stash->{book} = $book;
        
            # This is a hack to disable XSUB processing in Data::Dumper
            # (it's used in the view).  This is a work-around for a bug in
            # the interaction of some versions or Perl, Data::Dumper & DBIC.
            # You won't need this if you aren't using Data::Dumper (or if
            # you are running DBIC 0.06001 or greater), but adding it doesn't 
            # hurt anything either.
            $Data::Dumper::Useperl = 1;
        
            # Set the TT template to use
            $c->stash->{template} = 'books/create_done.tt2';
        } else {
            # Provide very simple feedback to the user
            $c->response->body('Unauthorized!');
        }
    }


To add authorization, we simply write the main code of this method in an C<if> statement that calls C<check_user_roles>.  If the user does not have the appropriate permissions, they receive an "Unauthorized!" message.  Note that we intentionally chose to display the message this way to demonstrate that TT templates will not be used if the response body has already been set.  In reality you would probably want to use a technique that maintains the visual continuity of your template layout (for example, using the "status" or "error" message feature added in Part 2).

B<TIP>: If you want to keep your existing C<url_create> method, you can create a new copy and comment out the original by making it look like a Pod comment.  For example, put something like C<=begin> before C<sub add : Local {> and C<=end> after the closing C<}>.


=head2 Try Out Authentication And Authorization

Press C<Ctrl-C> to kill the previous server instance (if it's still running) and restart it:

    $ script/myapp_server.pl

Now trying going to L<http://localhost:3000/books/list> and you should be taken to the login page (you might have to C<Shift+Reload> your browser).  Try logging in with both C<test01> and C<test02> (both use a password of C<mypass>) and notice how the roles information updates at the bottom of the "Book List" page. Also try the C<Logout> link on the book list page.

Now the "url_create" URL will work if you are already logged in as user C<test01>, but receive an authorization failure if you are logged in as C<test02>.  Try:

    http://localhost:3000/books/url_create/test/1/6

while logged in as each user.  Use one of the 'Logout' links (or go to L<http://localhost:3000/logout> in you browser directly) when you are done.


=head1 ENABLE ACL-BASED AUTHORIZATION

This section takes a brief look at how the L<Catalyst::Plugin::Authorization::ACL|Catalyst::Plugin::Authorization::ACL> can automate much of the work required to perform role-based authorization in a Catalyst application.


=head2 Add the C<Catalyst::Plugin::Authorization::ACL> Plugin

Open C<lib/MyApp.pm> in your editor and add the following plugin to the C<use Catalyst> statement:

    Authorization::ACL

Note that the remaining C<use Catalyst> plugins from earlier sections are not shown here, but they should still be included.


=head2 Add ACL Rules to the Application Class

Open C<lib/MyApp.pm> in your editor and add the following B<BELOW> the C<__PACKAGE__-E<gt>setup;> statement:

    # Authorization::ACL Rules
    __PACKAGE__->deny_access_unless(
            "/books/form_create",
            [qw/admin/],
        );
    __PACKAGE__->deny_access_unless(
            "/books/form_create_do",
            [qw/admin/],
        );
    __PACKAGE__->deny_access_unless(
            "/books/delete",
            [qw/user admin/],
        );

Each of the three statements above comprises an ACL plugin "rule".  The first two rules only allow admin-level users to create new books using the form (both the form itself and the data submission logic are protected).  The third statement allows both users and admin to delete books.  The C</books/url_create> action will continue to be protected by the "manually configured" authorization created earlier in this part of the tutorial.

The ACL plugin permits you to apply allow/deny logic in a variety of ways.  The following provides a basic overview of the capabilities:

=over 4

=item * 

The ACL plugin only operates on the Catalyst "private namespace".  You are using the private namespace when you use C<Local> actions.  C<Path>, C<Regex>, and C<Global> allow you to specify actions where the path and the namespace differ -- the ACL plugin will not work in these cases.

=item * 

Each rule is expressed in a separate C<__PACKAGE__-E<gt>deny_access_unless()> or C<__PACKAGE__-E<gt>allow_access_if()> line (there are several other methods that can be used for more complex policies, see the C<METHODS> portion of the L<Catalyst::Plugin::Authorization::ACL|Catalyst::Plugin::Authorization::ACL> documentation for more details).

=item * 

Each rule can contain multiple roles but only a single path.

=item * 

The rules are tried in order (with the "most specific" rules tested first), and processing stops at the first "match" where an allow or deny is specified.  Rules "fall through" if there is not a "match" (where a "match" means the user has the specified role).  If a "match" is found, then processing stops there and the appropriate allow/deny action is taken.

=item * 

If none of the rules match, then access is allowed.

=item * 

The rules currently need to be specific in the application class C<lib\MyApp.pm> B<after> the C<__PACKAGE__-E<gt>setup;> line.

=back


=head2 Add a Method to Handle Access Violations

By default, L<Catalyst::Plugin::Authorization::ACL|Catalyst::Plugin::Authorization::ACL> throws an exception when authorization fails.  This will take the user to the Catalyst debug screen, or a "Please come back later" message if you are not using the C<-Debug> flag. This step uses the C<access_denied> method in order to provide more appropriate feedback to the user.

Open C<lib/MyApp/Controller/Books.pm> in your editor and add the following method:

    =head2 access_denied
    
    Handle Catalyst::Plugin::Authorization::ACL access denied exceptions
    
    =cut
    
    sub access_denied : Private {
        my ($self, $c) = @_;
    
        # Set the error message
        $c->stash->{error_msg} = 'Unauthorized!';

        # Display the list
        $c->forward('list');
    }


Then run the Catalyst development server script:    

    $ script/myapp_server.pl

Log in as C<test02>.  Once at the book list, click the "Create" link to try the C<form_create> action.  You should receive a red "Unauthorized!" error message at the top of the list.  (Note that in reality you would probably want to place the "Create" link code in C<root/src/books/list.tt2> inside an C<IF> statement that only displays the list to admin-level users.)  If you log in as C<test01> you should be able to view the C<form_create> form and add a new book.

When you are done, use one of the 'Logout' links (or go to the L<http://localhost:3000/logout> URL directly) when you are done.


=head1 AUTHOR

Kennedy Clark, C<hkclark@gmail.com>

Please report any errors, issues or suggestions to the author.

Copyright 2006, Kennedy Clark. All rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Version: .94
Commit	Line	Data
4d583dd8	1	=head1 NAME
	2
	3	Catalyst::Manual::Tutorial::Authorization - Catalyst Tutorial Part 5: Authorization
	4
	5
	6
	7	=head1 OVERVIEW
	8
	9	This is B<Part 5 of 9> for the Catalyst tutorial.
	10
	11	L<Totorial Overview\|Catalyst::Manual::Tutorial>
	12
	13	=over 4
	14
	15	=item 1
	16
	17	L<Introduction\|Catalyst::Manual::Tutorial::Intro>
	18
	19	=item 2
	20
	21	L<Catalyst Basics\|Catalyst::Manual::Tutorial::CatalystBasics>
	22
	23	=item 3
	24
	25	L<Basic CRUD\|Catalyst::Manual::Tutorial03_BasicCRUD>
	26
	27	=item 4
	28
	29	L<Authentication\|Catalyst::Manual::Tutorial::Authentication>
	30
	31	=item 5
	32
	33	B<Authorization>
	34
	35	=item 6
	36
	37	L<Debugging\|Catalyst::Manual::Tutorial::Debugging>
	38
	39	=item 7
	40
	41	L<Testing\|Catalyst::Manual::Tutorial::Testing>
	42
	43	=item 8
	44
	45	L<AdvancedCRUD\|Catalyst::Manual::Tutorial::AdvancedCRUD>
	46
	47	=item 9
	48
	49	L<Appendicies\|Catalyst::Manual::Tutorial::Appendicies>
	50
	51	=back
	52
	53
	54
	55	=head1 DESCRIPTION
	56
	57	This part of the tutorial adds role-based authorization to the existing authentication implemented in Part 4. It provides simple examples of how to use roles in both TT templates and controller actions. The first half looks at manually configured authorization. The second half looks at how the ACL authorization plugin can simplify your code.
	58
	59	B<TIP>: Note that all of the code for this part of the tutorial can be pulled from the Catalyst Subversion repository in one step with the following command:
	60
	61	svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial@###
	62	IMPORTANT: Does not work yet. Will be completed for final version.
	63
	64
65
66	=head1 BASIC AUTHORIZATION
67
68	In this section you learn how to manually configure authorization.
69
70
71	=head2 Update Plugins to Include Support Authorization
72
73	Edit C<lib/MyApp.pm> and add C<Authorization::Roles> to the list:
74
75	use Catalyst qw/
76	-Debug
77	ConfigLoader
78	Static::Simple
79
80	Dumper
81	StackTrace
82	DefaultEnd
83
84	Authentication
85	Authentication::Store::DBIC
86	Authentication::Credential::Password
87	Authorization::Roles
88
89	Session
90	Session::Store::FastMmap
91	Session::State::Cookie
92	/;
93
94
95	=head2 Add Config Information for Authorization
96
97	Edit C<myapp.yml> and update it to match (everything from the "authorization:" line down is new):
98
99	---
100	name: MyApp
101	authentication:
102	dbic:
103	# Note this first definition would be the same as setting
104	# __PACKAGE__->config->{authentication}->{dbic}->{user_class} = 'MyAppDB::User'
105	# in lib/MyApp.pm (IOW, each hash key becomes a "name:" in the YAML file).
106	#
107	# This is the model object created by Catalyst::Model::DBIC from your
108	# schema (you created 'MyAppDB::User' but as the Catalyst startup
109	# debug messages show, it was loaded as 'MyApp::Model::MyAppDB::User').
110	# NOTE: Omit 'MyAppDB::Model' to avoid a component lookup issue in Catalyst 5.66
111	user_class: MyAppDB::User
112	# This is the name of the field in your 'users' table that contains the user's name
113	user_field: username
114	# This is the name of the field in your 'users' table that contains the password
115	password_field: password
116	# Other options can go here for hashed passwords
117	# Enabled hashed passwords
118	password_type: hashed
119	# Use the SHA-1 hashing algorithm
120	password_hash_type: SHA-1
121	authorization:
122	dbic:
123	# This is the model object created by Catalyst::Model::DBIC from your
124	# schema (you created 'MyAppDB::Role' but as the Catalyst startup
125	# debug messages show, it was loaded as 'MyApp::Model::MyAppDB::Role').
126	# NOTE: Omit 'MyAppDB::Model' to avoid a component lookup issue in Catalyst 5.66
127	role_class: MyAppDB::Role
128	# The name of the field in the 'roles' table that contains the role name
129	role_field: role
130	# The name of the accessor used to map a user to a role
131	# See the has_many() in MyAppDB/User.pm
132	role_rel: map_user_role
133	# The name of the field in the user_role table that references the user
134	user_role_user_field: user_id
135
136
137	=head2 Add Role-Specific Logic to the "Book List" Template
138
139	Open C<root/src/books/list.tt2> in your editor and add the following lines to the bottom of the file:
140
141	<p>Hello [% Catalyst.user.username %], you have the following roles:</p>
142
143	<ul>
144	[% # Dump list of roles -%]
145	[% FOR role = Catalyst.user.roles %]<li>[% role %]</li>[% END %]
146	</ul>
147
148	<p>
149	[% # Add some simple role-specific logic to template %]
150	[% # Use $c->check_user_roles() to check authz -%]
151	[% IF Catalyst.check_user_roles('user') %]
152	[% # Give normal users a link for 'logout' %]
153	<a href="[% Catalyst.uri_for('/logout') %]">Logout</a>
154	[% END %]
155
156	[% # Can also use $c->user->check_roles() to check authz -%]
157	[% IF Catalyst.check_user_roles('admin') %]
158	[% # Give admin users a link for 'create' %]
159	<a href="[% Catalyst.uri_for('form_create') %]">Create</a>
160	[% END %]
161	</p>
162
163	This code displays a different combination of links depending on the roles assigned to the user..
164
165
166	=head2 Limit C<Books::add> to C<admin> Users
167
168	C<IF> statements in TT templates simply control the output that is sent to the user's browser; it provides no real enforcement (if users know or guess the appropriate URLs, they are still perfectly free to hit any action within your application). We need to enhance the controller logic to wrap restricted actions with role validation logic.
169
170	For example, we might want to restrict the "formless create" action to admin-level users by editing C<lib/MyApp/Controller/Books.pm> and updating C<url_create> to match the following code:
171
172	=head2 url_create
173
174	Create a book with the supplied title, and rating
175	with manual authorization
176
177	=cut
178
179	sub url_create : Local {
180	# In addition to self & context, get the title, rating & author_id args
181	# from the URL. Note that Catalyst automatically puts extra information
182	# after the "/<controller_name>/<action_name/" into @_
183	my ($self, $c, $title, $rating, $author_id) = @_;
184
185	# Check the user's roles
186	if ($c->check_user_roles('admin')) {
187	# Call create() on the book model object. Pass the table
188	# columns/field values we want to set as hash values
189	my $book = $c->model('MyAppDB::Book')->create({
190	title => $title,
191	rating => $rating
192	});
193
194	# Add a record to the join table for this book, mapping to
195	# appropriate author
196	$book->add_to_book_authors({author_id => $author_id});
197	# Note: Above is a shortcut for this:
198	# $book->create_related('book_authors', {author_id => $author_id});
199
200	# Assign the Book object to the stash for display in the view
201	$c->stash->{book} = $book;
202
203	# This is a hack to disable XSUB processing in Data::Dumper
204	# (it's used in the view). This is a work-around for a bug in
205	# the interaction of some versions or Perl, Data::Dumper & DBIC.
206	# You won't need this if you aren't using Data::Dumper (or if
207	# you are running DBIC 0.06001 or greater), but adding it doesn't
208	# hurt anything either.
209	$Data::Dumper::Useperl = 1;
210
211	# Set the TT template to use
212	$c->stash->{template} = 'books/create_done.tt2';
213	} else {
214	# Provide very simple feedback to the user
215	$c->response->body('Unauthorized!');
216	}
217	}
218
219
220	To add authorization, we simply write the main code of this method in an C<if> statement that calls C<check_user_roles>. If the user does not have the appropriate permissions, they receive an "Unauthorized!" message. Note that we intentionally chose to display the message this way to demonstrate that TT templates will not be used if the response body has already been set. In reality you would probably want to use a technique that maintains the visual continuity of your template layout (for example, using the "status" or "error" message feature added in Part 2).
221
222	B<TIP>: If you want to keep your existing C<url_create> method, you can create a new copy and comment out the original by making it look like a Pod comment. For example, put something like C<=begin> before C<sub add : Local {> and C<=end> after the closing C<}>.
223
224
225	=head2 Try Out Authentication And Authorization
226
227	Press C<Ctrl-C> to kill the previous server instance (if it's still running) and restart it:
228
229	$ script/myapp_server.pl
230
231	Now trying going to L<http://localhost:3000/books/list> and you should be taken to the login page (you might have to C<Shift+Reload> your browser). Try logging in with both C<test01> and C<test02> (both use a password of C<mypass>) and notice how the roles information updates at the bottom of the "Book List" page. Also try the C<Logout> link on the book list page.
232
233	Now the "url_create" URL will work if you are already logged in as user C<test01>, but receive an authorization failure if you are logged in as C<test02>. Try:
234
235	http://localhost:3000/books/url_create/test/1/6
236
237	while logged in as each user. Use one of the 'Logout' links (or go to L<http://localhost:3000/logout> in you browser directly) when you are done.
238
239
240
241	=head1 ENABLE ACL-BASED AUTHORIZATION
242
243	This section takes a brief look at how the L<Catalyst::Plugin::Authorization::ACL\|Catalyst::Plugin::Authorization::ACL> can automate much of the work required to perform role-based authorization in a Catalyst application.
244
245
246	=head2 Add the C<Catalyst::Plugin::Authorization::ACL> Plugin
247
248	Open C<lib/MyApp.pm> in your editor and add the following plugin to the C<use Catalyst> statement:
249
250	Authorization::ACL
251
252	Note that the remaining C<use Catalyst> plugins from earlier sections are not shown here, but they should still be included.
253
254
255	=head2 Add ACL Rules to the Application Class
256
257	Open C<lib/MyApp.pm> in your editor and add the following B<BELOW> the C<__PACKAGE__-E<gt>setup;> statement:
258
259	# Authorization::ACL Rules
260	__PACKAGE__->deny_access_unless(
261	"/books/form_create",
262	[qw/admin/],
263	);
264	__PACKAGE__->deny_access_unless(
265	"/books/form_create_do",
266	[qw/admin/],
267	);
268	__PACKAGE__->deny_access_unless(
269	"/books/delete",
270	[qw/user admin/],
271	);
272
273	Each of the three statements above comprises an ACL plugin "rule". The first two rules only allow admin-level users to create new books using the form (both the form itself and the data submission logic are protected). The third statement allows both users and admin to delete books. The C</books/url_create> action will continue to be protected by the "manually configured" authorization created earlier in this part of the tutorial.
274
275	The ACL plugin permits you to apply allow/deny logic in a variety of ways. The following provides a basic overview of the capabilities:
276
277	=over 4
278
279	=item *
280
281	The ACL plugin only operates on the Catalyst "private namespace". You are using the private namespace when you use C<Local> actions. C<Path>, C<Regex>, and C<Global> allow you to specify actions where the path and the namespace differ -- the ACL plugin will not work in these cases.
282
283	=item *
284
285	Each rule is expressed in a separate C<__PACKAGE__-E<gt>deny_access_unless()> or C<__PACKAGE__-E<gt>allow_access_if()> line (there are several other methods that can be used for more complex policies, see the C<METHODS> portion of the L<Catalyst::Plugin::Authorization::ACL\|Catalyst::Plugin::Authorization::ACL> documentation for more details).
286
287	=item *
288
289	Each rule can contain multiple roles but only a single path.
290
291	=item *
292
293	The rules are tried in order (with the "most specific" rules tested first), and processing stops at the first "match" where an allow or deny is specified. Rules "fall through" if there is not a "match" (where a "match" means the user has the specified role). If a "match" is found, then processing stops there and the appropriate allow/deny action is taken.
294
295	=item *
296
297	If none of the rules match, then access is allowed.
298
299	=item *
300
301	The rules currently need to be specific in the application class C<lib\MyApp.pm> B<after> the C<__PACKAGE__-E<gt>setup;> line.
302
303	=back
304
305
306	=head2 Add a Method to Handle Access Violations
307
308	By default, L<Catalyst::Plugin::Authorization::ACL\|Catalyst::Plugin::Authorization::ACL> throws an exception when authorization fails. This will take the user to the Catalyst debug screen, or a "Please come back later" message if you are not using the C<-Debug> flag. This step uses the C<access_denied> method in order to provide more appropriate feedback to the user.
309
310	Open C<lib/MyApp/Controller/Books.pm> in your editor and add the following method:
311
312	=head2 access_denied
313
314	Handle Catalyst::Plugin::Authorization::ACL access denied exceptions
315
316	=cut
317
318	sub access_denied : Private {
319	my ($self, $c) = @_;
320
321	# Set the error message
322	$c->stash->{error_msg} = 'Unauthorized!';
323
324	# Display the list
325	$c->forward('list');
326	}
327
328
329	Then run the Catalyst development server script:
330
331	$ script/myapp_server.pl
332
333	Log in as C<test02>. Once at the book list, click the "Create" link to try the C<form_create> action. You should receive a red "Unauthorized!" error message at the top of the list. (Note that in reality you would probably want to place the "Create" link code in C<root/src/books/list.tt2> inside an C<IF> statement that only displays the list to admin-level users.) If you log in as C<test01> you should be able to view the C<form_create> form and add a new book.
334
335	When you are done, use one of the 'Logout' links (or go to the L<http://localhost:3000/logout> URL directly) when you are done.
336
337
338
339	=head1 AUTHOR
340
341	Kennedy Clark, C<hkclark@gmail.com>
342
343	Please report any errors, issues or suggestions to the author.
344
345	Copyright 2006, Kennedy Clark. All rights reserved.
346
347	This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
348
349	Version: .94
350