NAME¶
Dancer2::Manual - A gentle introduction to Dancer2
VERSION¶
version 0.152000
DESCRIPTION¶
Dancer2 is a free and open source web application framework written in Perl.
It's a complete rewrite of Dancer, based on Moo and using a more robust and
extensible fully-OO design.
It's designed to be powerful and flexible, but also easy to use - getting up and
running with your web app is trivial, and an ecosystem of adaptors for common
template engines, session storage, logging methods and plugins to make common
tasks easy mean you can do what you want to do, your way, easily.
INSTALL¶
Installation of Dancer2 is simple:
perl -MCPAN -e 'install Dancer2'
Thanks to the magic of cpanminus, if you do not have CPAN.pm configured, or just
want a quickfire way to get running, the following should work, at least on
Unix-like systems:
wget -O - http://cpanmin.us | sudo perl - Dancer2
(If you don't have root access, omit the 'sudo', and cpanminus will install
Dancer2 and prereqs into "~/perl5".)
BOOTSTRAPPING A NEW APP¶
Create a web application using the dancer script:
dancer2 -a MyApp && cd MyApp
And voila! You can now run the web application:
bin/app.pl
View the web application at:
http://localhost:3000
Note that as Dancer2 supports the PSGI specification, you can also use the
"plackup" tool (provided by Plack) for launching the application:
plackup ./bin/app.pl -p 5000
USAGE¶
When Dancer2 is imported to a script, that script becomes a webapp, and at this
point, all the script has to do is declare a list of
routes. A route
handler is composed by an HTTP method, a path pattern and a code block.
"strict" and "warnings" pragmas are also imported with
Dancer2.
The code block given to the route handler has to return a string which will be
used as the content to render to the client.
Routes are defined for a given HTTP method. For each method supported, a keyword
is exported by the module.
The following is an example of a route definition. The route is defined for the
method 'get', so only GET requests will be honoured by that route:
get '/hello/:name' => sub {
# do something
return "Hello ".param('name');
};
HTTP Methods¶
Here are some of the standard HTTP methods which you can use to define your
route handlers.
- GET The GET method retrieves information, and is the most
common
- GET requests should be used for typical "fetch" requests -
retrieving information. They should not be used for requests which change
data on the server or have other effects.
When defining a route handler for the GET method, Dancer2 automatically
defines a route handler for the HEAD method (in order to honour HEAD
requests for each of your GET route handlers).
To define a GET action, use the get keyword.
- POST The POST method is used to create a resource on the
server.
- To define a POST action, use the post keyword.
- PUT The PUT method is used to replace an existing resource.
- To define a PUT action, use the put keyword.
a PUT request should replace the existing resource with that specified - for
instance - if you wanted to just update an email address for a user, you'd
have to specify all attributes of the user again; to make a partial
update, a PATCH request is used.
- PATCH The PATCH method updates some attributes of an existing
resource.
- To define a PATCH action, use the patch keyword.
- DELETE The DELETE method requests that the origin server delete the
resource identified by the Request-URI.
- To define a DELETE action, use the del keyword.
To define a route for multiple methods you can also use the special keyword
any. This example illustrates how to define a route for both GET and
POST methods:
any ['get', 'post'] => '/myaction' => sub {
# code
};
Or even, a route handler that would match any HTTP methods:
any '/myaction' => sub {
# code
};
Route Handlers¶
The route action is the code reference declared. It can access parameters
through the "params" keyword, which returns a hashref. This hashref
is a merge of the route pattern matches and the request params.
You can have more details about how params are built and how to access them in
the Dancer2::Core::Request documentation.
Named Matching
A route pattern can contain one or more tokens (a word prefixed with ':'). Each
token found in a route pattern is used as a named-pattern match. Any match
will be set in the params hashref.
get '/hello/:name' => sub {
"Hey ".param('name').", welcome here!";
};
Tokens can be optional, for example:
get '/hello/:name?' => sub {
defined param('name') ? "Hello there ".param('name') : "whoever you are!";
};
Wildcards Matching
A route can contain a wildcard (represented by a "*"). Each wildcard
match will be returned in an arrayref, accessible via the "splat"
keyword.
get '/download/*.*' => sub {
my ($file, $ext) = splat;
# do something with $file.$ext here
};
Regular Expression Matching
A route can be defined with a Perl regular expression.
In order to tell Dancer2 to consider the route as a real regexp, the route must
be defined explicitly with "qr{}", like the following:
get qr{/hello/([\w]+)} => sub {
my ($name) = splat;
return "Hello $name";
};
Conditional Matching
Routes may include some matching conditions (on the useragent and the hostname
at the moment):
get '/foo', {agent => 'Songbird (\d\.\d)[\d\/]*?'} => sub {
'foo method for songbird'
}
get '/foo' => sub {
'all browsers except songbird'
}
Prefix¶
A prefix can be defined for each route handler, like this:
prefix '/home';
From here, any route handler is defined to /home/*
get '/page1' => sub {}; # will match '/home/page1'
You can unset the prefix value
prefix '/'; # or: prefix undef;
get '/page1' => sub {}; # will match /page1
Alternatively, to prevent you from ever forgetting to undef the prefix, you can
use lexical prefix like this:
prefix '/home' => sub {
get '/page1' => sub {}; # will match '/home/page1'
}; ## prefix reset to previous value on exit
get '/page1' => sub {}; # will match /page1
Action Skipping¶
An action can choose not to serve the current request and ask Dancer2 to process
the request with the next matching route.
This is done with the
pass keyword, like in the following example
get '/say/:word' => sub {
return pass if (params->{word} =~ /^\d+$/);
"I say a word: ".params->{word};
};
get '/say/:number' => sub {
"I say a number: ".params->{number};
};
Default Error Pages¶
When an error is rendered (the action responded with a status code different
than 200), Dancer2 first looks in the public directory for an HTML file
matching the error code (eg: 500.html or 404.html).
If such a file exists, it's used to render the error, otherwise, a default error
page will be rendered on the fly.
Execution Errors¶
When an error occurs during the route execution, Dancer2 will render an error
page with the HTTP status code 500.
It's possible either to display the content of the error message or to hide it
with a generic error page.
This is a choice left to the end-user and can be set with the
show_errors
setting.
Note that you can also choose to consider all warnings in your route handlers as
errors when the setting
warnings is set to 1.
HOOKS¶
Hooks are code references (or anonymous subroutines) that are triggered at
specific moments during the resolution of a request.
Many of them are supported by the core but plugins and engines can also define
their own.
Request workflow¶
"before" hooks are evaluated before each request within the context of
the request and receives as argument the app (a Dancer2::Core::App object).
It's possible to define variables which will be accessible in the action blocks
with the keyword "var".
hook before => sub {
var note => 'Hi there';
};
get '/foo/*' => sub {
my ($match) = splat; # 'oversee';
vars->{note}; # 'Hi there'
};
For another example, this can be used along with session support to easily give
non-logged-in users a login page:
hook before => sub {
if (!session('user') && request->dispatch_path !~ m{^/login}) {
# Pass the original path requested along to the handler:
forward '/login', { requested_path => request->dispatch_path };
}
};
The request keyword returns the current Dancer2::Core::Request object
representing the incoming request.
"after" hooks are evaluated after the response has been built by a
route handler, and can alter the response itself, just before it's sent to the
client.
This hook runs after a request has been processed, but before the response is
sent.
It receives a Dancer2::Core::Response object, which it can modify if it needs to
make changes to the response which is about to be sent.
The filter is given the response object as its first argument:
hook after => sub {
my $response = shift;
$response->(content, 'after filter got here!');
};
Templates¶
"before_template_render" hooks are called whenever a template is going
to be processed, they are passed the tokens hash which they can alter.
hook before_template_render => sub {
my $tokens = shift;
$tokens->{foo} = 'bar';
}
The tokens hash will then be passed to the template with all the modifications
performed by the filter. This is a good way to setup some global vars you like
to have in all your templates, like the name of the user logged in or a
section name.
"after_template_render" hooks are called after the view has been
rendered. They receive as their first argument the reference to the content
that has been produced. This can be used to post-process the content rendered
by the template engine.
hook after_template_render => sub {
my $ref_content = shift;
my $content = $$ref_content;
# do something with $content
$ref_content = \$content;
};
"before_layout_render" hooks are called whenever the layout is going
to be applied to the current content. The arguments received by the hook are
the current tokens hashref and a reference to the current content.
hook before_layout_render => sub {
my ($tokens, $ref_content) = @_;
$tokens->{new_stuff} = 42;
$ref_conent = \"new content";
};
"after_layout_render" hooks are called once the complete content of
the view has been produced, after the layout has been applied to the content.
The argument received by the hook is a reference to the complete content
string.
hook after_layout_render => sub {
my $ref_content = shift;
...
};
Error handling¶
When an error is caught by Dancer2's core, an exception object is built (of the
class Dancer2::Core::Error). This class provides hook to let the user alter
the error work-flow if needed.
"init_error" hooks are called whenever an error object is built, the
object is passed to the hook.
hook init_error => sub {
my $error = shift;
# do something with $error
};
This hook was named before_error_init in Dancer, and is
now aliased to this hook.
"before_error" hooks are called whenever an error is going to be
thrown, it receives the error object as its first and unique argument.
hook before_error => sub {
my $error = shift;
# do something with $error
};
This hook was named before_error_render in Dancer, and
is now aliased to this hook.
"after_error" hooks are called whenever an error object has been
thrown, it receives a Dancer2::Core::Response object as the first argument.
hook after_error => sub {
my $response = shift;
};
This hook was named <after_error_render in Dancer, and is now aliased
to this hook.>
"on_route_exception" is called when an exception has been caught, at
the route level, just before rethrowing it higher. This hook receives a
Dancer2::Core::App and the error as arguments.
hook on_route_exception => sub {
my ($app, $error) = @_;
};
File rendering¶
Whenever a content is produced out of the parsing of a static file, the
Dancer2::Handler::File component is used. This component provides two hooks,
"before_file_render" and "after_file_render".
"before_file_render" hooks are called just before starting to parse
the file, the hook receives as its first argument the file path that is going
to be processed.
hook before_file_render => sub {
my $path = shift;
};
"after_file_render" are called after the file has been parsed and the
response content produced. It receives the response object
(Dancer2::Core::Response) produced.
hook after_file_render => sub {
my $response = shift;
};
Serializers¶
"before_serializer" is called before serializing the content, and
receives as argument the content to serialize.
hook before_serializer => sub {
my $content = shift;
...
};
"after_serializer" is called after the payload was serialized, and
receives the serialized content as an argument.
hook after_serializer => sub {
my $content = shift;
...
};
CONFIGURATION AND ENVIRONMENTS¶
Configuring a Dancer2 application can be done in many ways. The easiest one (and
maybe the dirtiest) is to put all your settings statements at the top of your
script, before calling the
dance() method.
Other ways are possible. You could write all your setting calls in the file
`appdir/config.yml'. You would, of course, have write the conffile in YAML.
While better than the first option, it's still not perfect. You can't easily
switch from an environment to another (for example, from development to
production) without rewriting the config.yml file. The best way is to have one
config.yml file with default global settings, like the following:
# appdir/config.yml
logger: 'file'
layout: 'main'
And then write as many environment files as you like in appdir/environments.
That way, the appropriate environment config file will be loaded according to
the running environment (if none is specified, 'development' is assumed).
Note that you can change the running environment using the --environment
commandline switch.
Typically, you'll want to set the following values in a development config file:
# appdir/environments/development.yml
log: 'debug'
startup_info: 1
show_errors: 1
And in a production one:
# appdir/environments/production.yml
log: 'warning'
startup_info: 0
show_errors: 0
Please note that you are not limited to writing configuration files in YAML.
Dancer2 supports any file format that is supported by Config::Any, such as
JSON, XML, INI files, and Apache-style config files.
Accessing configuration data¶
A Dancer2 application can access the information from its config file easily
with the config keyword:
get '/appname' => sub {
return "This is " . config->{appname};
};
Settings¶
It's possible to change quite every parameter of the application via the
settings mechanism.
A setting is key/value pair assigned by the keyword
set:
set setting_name => 'setting_value';
More usefully, settings can be defined in a configuration file.
Environment-specific settings can also be defined in environment-specific
files (for instance, you do not want to show error stacktraces in production,
and might want extra logging in development). See the cookbook for examples.
Serializers¶
When writing a webservice, data serialization/deserialization is a common issue
to deal with. Dancer2 can automatically handle that for you, via a serializer.
When setting up a serializer, a new behaviour is authorized for any route
handler you define: any non-scalar response will be rendered as a serialized
string, via the current serializer.
Here is an example of a route handler that will return a HashRef
use Dancer2;
set serializer => 'JSON';
get '/user/:id/' => sub {
{ foo => 42,
number => 100234,
list => [qw(one two three)],
}
};
As soon as the content is not a scalar - and a serializer is set, which is not
the case by default - Dancer2 renders the response via the current serializer.
Hence, with the JSON serializer set, the route handler above would result in a
content like the following:
{"number":100234,"foo":42,"list":["one","two","three"]}
The following serializers are available, be aware they dynamically depend on
Perl modules you may not have on your system.
- JSON
- requires JSON
- YAML
- requires YAML
- XML
- requires XML::Simple
- Mutable
- will try to find the appropriate serializer using the Content-Type
and Accept-type header of the request.
Logging¶
It's possible to log messages sent by the application. In the current version,
only one method is possible for logging messages but future releases may add
additional logging methods, for instance logging to syslog.
In order to enable the logging system for your application, you first have to
start the logger engine in your config file:
logger: 'file'
Then you can choose which kind of messages you want to actually log:
log: 'core' # will log all messages, including some from Dancer2 itself
log: 'debug' # will log debug, info, warning and errors
log: 'info' # will log info, warning and errors
log: 'warning' # will log warning and errors
log: 'error' # will log only errors
A directory appdir/logs will be created and will host one logfile per
environment. The log message contains the time it was written, the PID of the
current process, the message and the caller information (file and line).
To log messages, use the "debug", "info",
"warning" and "error" methods, for instance:
debug "This is a debug message";
Using Templates¶
Views
It's possible to render the action's content with a template; this is called a
view. The `appdir/views' directory is the place where views are located.
You can change this location by changing the setting 'views', for instance if
your templates are located in the 'templates' directory, do the following:
set views => path(dirname(__FILE__), 'templates');
By default, the internal template engine is used (Dancer2::Template::Simple) but
you may want to upgrade to Template::Toolkit. If you do so, you have to enable
this engine in your settings as explained in
Dancer2::Template::TemplateToolkit. If you do so, you'll also have to import
the Template module in your application code.
In order to render a view, just call the 'template' keyword at the end of the
action by giving the view name and the HASHREF of tokens to interpolate in the
view (note that the request, session and route params are automatically
accessible in the view, named request, session and params):
use Dancer2;
use Template;
get '/hello/:name' => sub {
template 'hello' => { number => 42 };
};
And the appdir/views/hello.tt view can contain the following code:
<html>
<head></head>
<body>
<h1>Hello [% params.name %]</h1>
<p>Your lucky number is [% number %]</p>
<p>You are using [% request.user_agent %]</p>
[% IF session.user %]
<p>You're logged in as [% session.user %]</p>
[% END %]
</body>
</html>
By default, views use a ".tt" extension. This can be overridden by
setting the "extension" attribute in the template engine
configuration like so:
set engines => {
template => {
template_toolkit => {
extension => 'foo',
},
},
};
Layouts
A layout is a special view, located in the 'layouts' directory (inside the views
directory) which must have a token named `content'. That token marks the place
where to render the action view. This lets you define a global layout for your
actions. Any tokens that you defined when you called the 'template' keyword
are available in the layouts, as well as the standard session, request, and
params tokens. This allows you to insert per-page content into the HTML
boilerplate, such as page titles, current-page tags for navigation, etc.
Here is an example of a layout: views/layouts/main.tt:
<html>
<head>[% page_title %]</head>
<body>
<div id="header">
...
</div>
<div id="content">
[% content %]
</div>
</body>
</html>
This layout can be used like the following:
use Dancer2;
set layout => 'main';
get '/' => sub {
template 'index' => { page_title => "Your website Homepage" };
};
Of course, if a layout is set, it can also be disabled for a specific action,
like the following:
use Dancer2;
set layout => 'main';
get '/nolayout' => sub {
template 'some_ajax_view',
{ tokens_var => "42" },
{ layout => 0 };
};
Static Files¶
Static Directory
Static files are served from the ./public directory. You can specify a different
location by setting the 'public' option:
set public => path(dirname(__FILE__), 'static');
Note that the public directory name is not included in the URL. A file
./public/css/style.css is made available as example.com/css/style.css.
Static File from a Route Handler
It's possible for a route handler to send a static file, as follows:
get '/download/*' => sub {
my $params = shift;
my ($file) = @{ $params->{splat} };
send_file $file;
};
Or even if you want your index page to be a plain old index.html file, just do:
get '/' => sub {
send_file '/index.html'
};
EXPORTS¶
By default, "use Dancer2" exports all the DSL keywords and sets up the
webapp under the name of the current package. The following tags control
exports and webapp namespace.
- !keyword
- If you want to prevent Dancer2 from exporting specific keywords; perhaps
you plan to implement them yourself in a different way, or they clash with
another module you're loading, you can simply exclude them:
use Test::More;
use Dancer2 qw(!pass);
The above would import all keywords as normal, with the exception of
"pass".
- appname
- A larger application may split its source between several packages to aid
maintainability. Dancer2 will create a separate application for each
package, each having separate hooks, config and/or engines. You can force
Dancer2 to collect the route and hooks into a single application with the
"appname" tag; e.g.
package MyApp;
use Dancer2;
get '/foo' => sub {...};
package MyApp::Private;
use Dancer2 appname => MyApp;
get '/bar' => sub {...};
The above would add the "bar" route to the MyApp application.
Dancer2 will not create an application with the name
"MyApp::Private".
When you "use Dancer2", you get an "import" method added
into the current package. This
will override previously declared import
methods from other sources, such as Exporter. Dancer2 applications support the
following tags on import:
- with
- The "with" tag allows an app to pass one or more config entries
to another app, when it "use"s it.
package MyApp;
use Dancer2;
set session => 'YAML';
use Blog with => { session => engine('session') };
In this example, the session engine is passed to the "Blog" app.
That way, anything done in the session will be shared between both apps.
Anything that is defined in the config entry can be passed that way. If we
want to pass the whole config object, it can be done like so:
use SomeApp with => { %{config()} };
DSL KEYWORDS¶
Dancer2 provides you with a DSL (Domain-Specific Language) which makes
implementing your web application trivial.
For example, take the following example:
use Dancer2;
get '/hello/:name' => sub {
my $name = params->{name};
};
dance;
"get" and "params" are keywords provided by Dancer2.
This document lists all keywords provided by Dancer2. It does not cover
additional keywords which may be provided by loaded plugins; see the
documentation for plugins you use to see which additional keywords they make
available to you.
any¶
Defines a route for multiple HTTP methods at once:
any ['get', 'post'] => '/myaction' => sub {
# code
};
Or even, a route handler that would match any HTTP methods:
any '/myaction' => sub {
# code
};
cookies¶
Accesses cookies values, it returns a HashRef of Dancer2::Core::Cookie objects:
get '/some_action' => sub {
my $cookie = cookies->{name};
return $cookie->value;
};
In the case you have stored something else than a Scalar in your cookie:
get '/some_action' => sub {
my $cookie = cookies->{oauth};
my %values = $cookie->value;
return ($values{token}, $values{token_secret});
};
cookie¶
Accesses a cookie value (or sets it). Note that this method will eventually be
preferred over "set_cookie".
cookie lang => "fr-FR"; # set a cookie and return its value
cookie lang => "fr-FR", expires => "2 hours"; # extra cookie info
cookie "lang" # return a cookie value
If your cookie value is a key/value URI string, like
token=ABC&user=foo
"cookie" will only return the first part ("token=ABC") if
called in scalar context. Use list context to fetch them all:
my @values = cookie "name";
config¶
Accesses the configuration of the application:
get '/appname' => sub {
return "This is " . config->{appname};
};
content¶
Sets the content for the response.
get '/' => sub {
content 'Hello, world!';
# the return value of the route is ignored
return 'Ignored String';
};
Once you set the content using the keyword, your return value (which is usually
the content) is ignored.
WARNING : If you are using the "pass" keyword, the last route
will be in charge of setting the content.
content_type¶
Sets the
content-type rendered, for the current route handler:
get '/cat/:txtfile' => sub {
content_type 'text/plain';
# here we can dump the contents of param('txtfile')
};
You can use abbreviations for content types. For instance:
get '/svg/:id' => sub {
content_type 'svg';
# here we can dump the image with id param('id')
};
Note that if you want to change the default content-type for every route, you
have to change the "content_type" setting instead.
dance¶
Alias for the "start" keyword.
dancer_version¶
Returns the version of Dancer. If you need the major version, do something like:
int(dancer_version);
debug¶
Logs a message of debug level:
debug "This is a debug message";
See Dancer2::Core::Role::Logger for details on how to configure where log
messages go.
dirname¶
Returns the dirname of the path given:
my $dir = dirname($some_path);
engine¶
Given a namespace, returns the current engine object
my $template_engine = engine 'template';
my $html = $template_engine->apply_renderer(...);
$template_engine->apply_layout($html);
error¶
Logs a message of error level:
error "This is an error message";
See Dancer2::Core::Role::Logger for details on how to configure where log
messages go.
false¶
Constant that returns a false value (0).
forward¶
Runs an "internal redirect" of the current request to another request.
More formally; when the "forward" is executed, the current dispatch
of the request is aborted, the request is modified (altering query params or
request method), and the modified request is dispatched again. Any remaining
code (route and hooks) from the current dispatch will never be run and the
modified request's dispatch will execute hooks for the new request normally.
It effectively lets you chain routes together in a clean manner.
get '/demo/articles/:article_id' => sub {
# you'll have to implement this next sub yourself :)
change_the_main_database_to_demo();
forward "/articles/" . params->{article_id};
};
In the above example, the users that reach
/demo/articles/30 will
actually reach
/articles/30 but we've changed the database to demo
before.
This is pretty cool because it lets us retain our paths and offer a demo
database by merely going to
/demo/....
You'll notice that in the example we didn't indicate whether it was
GET
or
POST. That is because "forward" chains the same type of
route the user reached. If it was a
GET, it will remain a
GET
(but if you do need to change the method, you can do so; read on below for
details.)
WARNING : Any code after a "forward" is ignored, until the end
of the route. It's not necessary to use "return" with
"forward" anymore.
get '/foo/:article_id' => sub {
if ($condition) {
forward "/articles/" . params->{article_id};
# The following code WILL NOT BE executed
do_stuff();
}
more_stuff();
};
Note that "forward" doesn't parse GET arguments. So, you can't use
something like:
forward '/home?authorized=1';
But "forward" supports an optional HashRef with parameters to be added
to the actual parameters:
forward '/home', { authorized => 1 };
Finally, you can add some more options to the "forward" method, in a
third argument, also as a HashRef. That option is currently only used to
change the method of your request. Use with caution.
forward '/home', { auth => 1 }, { method => 'POST' };
from_dumper ($structure)¶
Deserializes a Data::Dumper structure.
from_json ($structure, \%options)¶
Deserializes a JSON structure. Can receive optional arguments. Those arguments
are valid JSON arguments to change the behaviour of the default
"JSON::from_json" function.
from_yaml ($structure)¶
Deserializes a YAML structure.
get¶
Defines a route for HTTP
GET requests to the given path:
get '/' => sub {
return "Hello world";
}
Note that a route to match
HEAD requests is automatically created as
well.
halt¶
Sets a response object with the content given.
When used as a return value from a filter, this breaks the execution flow and
renders the response immediately:
hook before => sub {
if ($some_condition) {
halt("Unauthorized");
# This code is not executed :
do_stuff();
}
};
get '/' => sub {
"hello there";
};
WARNING : Issuing a halt immediately exits the current route, and perform
the halt. Thus, any code after a halt is ignored, until the end of the route.
So it's not necessary anymore to use "return" with halt.
Adds custom headers to responses:
get '/send/headers', sub {
headers 'X-Foo' => 'bar', X-Bar => 'foo';
}
adds a custom header to response:
get '/send/header', sub {
header 'x-my-header' => 'shazam!';
}
Note that it will overwrite the old value of the header, if any. To avoid that,
see "push_header".
Do the same as "header", but allow for multiple headers with the same
name.
get '/send/header', sub {
push_header 'x-my-header' => '1';
push_header 'x-my-header' => '2';
will result in two headers "x-my-header" in the response
}
hook¶
Adds a hook at some position. For example :
hook before_serializer => sub {
my $content = shift;
...
};
There can be multiple hooks assigned to a given position, and each will be
executed in order.
info¶
Logs a message of info level:
info "This is a info message";
See Dancer2::Core::Role::Logger for details on how to configure where log
messages go.
load¶
Loads one or more perl scripts in the current application's namespace. Syntactic
sugar around Perl's "require":
load 'UserActions.pl', 'AdminActions.pl';
mime¶
Shortcut to access the instance object of Dancer2::Core::MIME. You should read
the Dancer2::Core::MIME documentation for full details, but the most
commonly-used methods are summarized below:
# set a new mime type
mime->add_type( foo => 'text/foo' );
# set a mime type alias
mime->add_alias( f => 'foo' );
# get mime type for an alias
my $m = mime->for_name( 'f' );
# get mime type for a file (based on extension)
my $m = mime->for_file( "foo.bar" );
# get current defined default mime type
my $d = mime->default;
# set the default mime type using config.yml
# or using the set keyword
set default_mime_type => 'text/plain';
params¶
This method should be called from a route handler. It's an alias for the
Dancer2::Core::Request params accessor. It returns a hash (in list context) or
a hash reference (in scalar context) to all defined parameters. Check
"param" below to access quickly to a single parameter value.
param¶
This method should be called from a route handler. This method is an
accessor to the parameters hash table.
post '/login' => sub {
my $username = param "user";
my $password = param "pass";
# ...
}
pass¶
This method should be called from a route handler. Tells Dancer to pass
the processing of the request to the next matching route.
WARNING : Issuing a pass immediately exits the current route, and perform
the pass. Thus, any code after a pass is ignored, until the end of the route.
So it's not necessary anymore to use "return" with pass.
get '/some/route' => sub {
if (...) {
# we want to let the next matching route handler process this one
pass(...);
# This code will be ignored
do_stuff();
}
};
WARNING : You cannot set the content before passing and have it remain,
even if you use the "content" keyword or set it directly in the
response object.
patch¶
Defines a route for HTTP
PATCH requests to the given URL:
patch '/resource' => sub { ... };
("PATCH" is a relatively new and not-yet-common HTTP verb, which is
intended to work as a "partial-PUT", transferring just the changes;
please see <
http://tools.ietf.org/html/rfc5789|RFC5789> for further
details.)
Please be aware that, if you run your app in standalone mode, "PATCH"
requests will not reach your app unless you have a new version of
HTTP::Server::Simple which accepts "PATCH" as a valid verb. The
current version at time of writing, 0.44, does not. A pull request has been
submitted to add this support, which you can find at:
<
https://github.com/bestpractical/http-server-simple/pull/1>
path¶
Concatenates multiple paths together, without worrying about the underlying
operating system:
my $path = path(dirname($0), 'lib', 'File.pm');
It also normalizes (cleans) the path aesthetically. It does not verify the path
exists.
post¶
Defines a route for HTTP
POST requests to the given URL:
post '/' => sub {
return "Hello world";
}
prefix¶
Defines a prefix for each route handler, like this:
prefix '/home';
From here, any route handler is defined to /home/*:
get '/page1' => sub {}; # will match '/home/page1'
You can unset the prefix value:
prefix undef;
get '/page1' => sub {}; # will match /page1
For a safer alternative you can use lexical prefix like this:
prefix '/home' => sub {
## Prefix is set to '/home' here
get ...;
get ...;
};
## prefix reset to the previous version here
This makes it possible to nest prefixes:
prefix '/home' => sub {
## some routes
prefix '/private' => sub {
## here we are under /home/private...
## some more routes
};
## back to /home
};
## back to the root
Notice: once you have a prefix set, do not add a caret to the regex:
prefix '/foo';
get qr{^/bar} => sub { ... } # BAD BAD BAD
get qr{/bar} => sub { ... } # Good!
del¶
Defines a route for HTTP
DELETE requests to the given URL:
del '/resource' => sub { ... };
options¶
Defines a route for HTTP
OPTIONS requests to the given URL:
options '/resource' => sub { ... };
put¶
Defines a route for HTTP
PUT requests to the given URL:
put '/resource' => sub { ... };
redirect¶
Generates a HTTP redirect (302). You can either redirect to a complete different
site or within the application:
get '/twitter', sub {
redirect 'http://twitter.com/me';
# Any code after the redirect will not be executed.
};
WARNING : Issuing a "redirect" immediately exits the current
route. Thus, any code after a "redirect" is ignored, until the end
of the route. So it's not necessary anymore to use "return" with
"redirect".
You can also force Dancer to return a specific 300-ish HTTP response code:
get '/old/:resource', sub {
redirect '/new/'.params->{resource}, 301;
};
request¶
Returns a Dancer2::Core::Request object representing the current request.
See the Dancer2::Core::Request documentation for the methods you can call, for
example:
request->referer; # value of the HTTP referer header
request->remote_address; # user's IP address
request->user_agent; # User-Agent header value
send_error¶
Returns a HTTP error. By default the HTTP code returned is 500:
get '/photo/:id' => sub {
if (...) {
send_error("Not allowed", 403);
} else {
# return content
}
}
WARNING : Issuing a send_error immediately exits the current route, and
perform the send_error. Thus, any code after a send_error is ignored, until
the end of the route. So it's not necessary anymore to use "return"
with send_error.
get '/some/route' => sub {
if (...) {
# we want to let the next matching route handler process this one
send_error(..);
# This code will be ignored
do_stuff();
}
};
send_file¶
Lets the current route handler send a file to the client. Note that the path of
the file must be relative to the
public directory unless you use the
"system_path" option (see below).
get '/download/:file' => sub {
return send_file(params->{file});
}
WARNING : Issuing a send_file immediately exits the current route, and
perform the send_file. Thus, any code after a send_file is ignored, until the
end of the route. So it's not necessary anymore to use "return" with
send_file.
get '/some/route' => sub {
if (...) {
# we want to let the next matching route handler process this one
send_file(...);
# This code will be ignored
do_stuff();
}
};
Send file supports streaming possibility using PSGI streaming. The server should
support it but normal streaming is supported on most, if not all.
get '/download/:file' => sub {
return send_file( params->{file}, streaming => 1 );
}
You can control what happens using callbacks.
First, "around_content" allows you to get the writer object and the
chunk of content read, and then decide what to do with each chunk:
get '/download/:file' => sub {
return send_file(
params->{file},
streaming => 1,
callbacks => {
around_content => sub {
my ( $writer, $chunk ) = @_;
$writer->write("* $chunk");
},
},
);
}
You can use "around" to get all the content (whether a filehandle if
it's a regular file or a full string if it's a scalar ref) and decide what to
do with it:
get '/download/:file' => sub {
return send_file(
params->{file},
streaming => 1,
callbacks => {
around => sub {
my ( $writer, $content ) = @_;
# we know it's a text file, so we'll just stream
# line by line
while ( my $line = <$content> ) {
$writer->write($line);
}
},
},
);
}
Or you could use "override" to control the entire streaming callback
request:
get '/download/:file' => sub {
return send_file(
params->{file},
streaming => 1,
callbacks => {
override => sub {
my ( $respond, $response ) = @_;
my $writer = $respond->( [ $newstatus, $newheaders ] );
$writer->write("some line");
},
},
);
}
You can also set the number of bytes that will be read at a time (default being
42K bytes) using "bytes":
get '/download/:file' => sub {
return send_file(
params->{file},
streaming => 1,
bytes => 524288, # 512K
);
};
The content-type will be set depending on the current MIME types definition (see
"mime" if you want to define your own).
If your filename does not have an extension, or you need to force a specific
mime type, you can pass it to "send_file" as follows:
return send_file(params->{file}, content_type => 'image/png');
Also, you can use your aliases or file extension names on
"content_type", like this:
return send_file(params->{file}, content_type => 'png');
For files outside your
public folder, you can use the
"system_path" switch. Just bear in mind that its use needs caution
as it can be dangerous.
return send_file('/etc/passwd', system_path => 1);
If you have your data in a scalar variable, "send_file" can be useful
as well. Pass a reference to that scalar, and "send_file" will
behave as if there was a file with that contents:
return send_file( \$data, content_type => 'image/png' );
Note that Dancer is unable to guess the content type from the data contents.
Therefore you might need to set the "content_type" properly. For
this kind of usage an attribute named "filename" can be useful. It
is used as the Content-Disposition header, to hint the browser about the
filename it should use.
return send_file( \$data, content_type => 'image/png'
filename => 'onion.png' );
Note that you should always use "return send_file ..." to stop
execution of your route handler at that point.
set¶
Defines a setting:
set something => 'value';
You can set more than one value at once:
set something => 'value', otherthing => 'othervalue';
setting¶
Returns the value of a given setting:
setting('something'); # 'value'
session¶
Provides access to all data stored in the user's session (if any).
It can also be used as a setter to store data in the session:
# getter example
get '/user' => sub {
if (session('user')) {
return "Hello, ".session('user')->name;
}
};
# setter example
post '/user/login' => sub {
...
if ($logged_in) {
session user => $user;
}
...
};
You may also need to clear a session:
# destroy session
get '/logout' => sub {
...
app->destroy_session;
...
};
If you need to fetch the session ID being used for any reason:
my $id = session->id;
splat¶
Returns the list of captures made from a route handler with a route pattern
which includes wildcards:
get '/file/*.*' => sub {
my ($file, $extension) = splat;
...
};
There is also the extensive splat (A.K.A. "megasplat"), which allows
extensive greedier matching, available using two asterisks. The additional
path is broken down and returned as an ArrayRef:
get '/entry/*/tags/**' => sub {
my ( $entry_id, $tags ) = splat;
my @tags = @{$tags};
};
This helps with chained actions:
get '/team/*/**' => sub {
my ($team) = splat;
var team => $team;
pass;
};
prefix '/team/*';
get '/player/*' => sub {
my ($player) = splat;
# etc...
};
get '/score' => sub {
return score_for( vars->{'team'} );
};
start¶
Starts the application or the standalone server (depending on the deployment
choices).
This keyword should be called at the very end of the script, once all routes are
defined. At this point, Dancer takes over control.
to_app¶
Returns the PSGI coderef for the current (and only the current) application.
You can call it as a method on the class or as a DSL:
my $app = MyApp->to_app;
# or
my $app = to_app;
psgi_app¶
Provides the same functionality as "to_app" but uses the deprecated
Dispatcher engine. You should use "to_app".
status¶
Changes the status code provided by an action. By default, an action will
produce an "HTTP 200 OK" status code, meaning everything is OK:
get '/download/:file' => {
if (! -f params->{file}) {
status 'not_found';
return "File does not exist, unable to download";
}
# serving the file...
};
In that example, Dancer will notice that the status has changed, and will render
the response accordingly.
The status keyword receives either a numeric status code or its name in lower
case, with underscores as a separator for blanks - see the list in "HTTP
CODES" in Dancer2::Core::HTTP.
template¶
Returns the response of processing the given template with the given parameters
(and optional settings), wrapping it in the default or specified layout too,
if layouts are in use.
An example of a route handler which returns the result of using template to
build a response with the current template engine:
get '/' => sub {
...
return template 'some_view', { token => 'value'};
};
Note that "template" simply returns the content, so when you use it in
a route handler, if execution of the route handler should stop at that point,
make sure you use 'return' to ensure your route handler returns the content.
Since template just returns the result of rendering the template, you can also
use it to perform other templating tasks, e.g. generating emails:
post '/some/route' => sub {
if (...) {
email {
to => 'someone@example.com',
from => 'foo@example.com',
subject => 'Hello there',
msg => template('emails/foo', { name => params->{name} }),
};
return template 'message_sent';
} else {
return template 'error';
}
};
Compatibility notice: "template" was changed in version 1.3090 to
immediately interrupt execution of a route handler and return the content, as
it's typically used at the end of a route handler to return content. However,
this caused issues for some people who were using "template" to
generate emails etc, rather than accessing the template engine directly, so
this change has been reverted in 1.3091.
The first parameter should be a template available in the views directory, the
second one (optional) is a HashRef of tokens to interpolate, and the third
(again optional) is a HashRef of options.
For example, to disable the layout for a specific request:
get '/' => sub {
template 'index', {}, { layout => undef };
};
Or to request a specific layout, of course:
get '/user' => sub {
template 'user', {}, { layout => 'user' };
};
Some tokens are automatically added to your template ("perl_version",
"dancer_version", "settings", "request",
"params", "vars" and, if you have sessions enabled,
"session"). Check Dancer2::Core::Role::Template for further details.
to_dumper ($structure)¶
Serializes a structure with Data::Dumper.
Calling this function will
not trigger the serialization's hooks.
to_json ($structure, \%options)¶
Serializes a structure to JSON. Can receive optional arguments. Thoses arguments
are valid JSON arguments to change the behaviour of the default
"JSON::to_json" function.
Calling this function will
not trigger the serialization's hooks.
to_yaml ($structure)¶
Serializes a structure to YAML.
Calling this function will
not trigger the serialization's hooks.
true¶
Constant that returns a true value (1).
upload¶
Provides access to file uploads. Any uploaded file is accessible as a
Dancer2::Core::Request::Upload object. You can access all parsed uploads via:
post '/some/route' => sub {
my $file = upload('file_input_foo');
# file is a Dancer2::Core::Request::Upload object
};
If you named multiple input of type "file" with the same name, the
upload keyword will return an Array of Dancer2::Core::Request::Upload objects:
post '/some/route' => sub {
my ($file1, $file2) = upload('files_input');
# $file1 and $file2 are Dancer2::Core::Request::Upload objects
};
You can also access the raw HashRef of parsed uploads via the current request
object:
post '/some/route' => sub {
my $all_uploads = request->uploads;
# $all_uploads->{'file_input_foo'} is a Dancer2::Core::Request::Upload object
# $all_uploads->{'files_input'} is an ArrayRef of Dancer2::Core::Request::Upload objects
};
Note that you can also access the filename of the upload received via the params
keyword:
post '/some/route' => sub {
# params->{'files_input'} is the filename of the file uploaded
};
See Dancer2::Core::Request::Upload for details about the interface provided.
uri_for¶
Returns a fully-qualified URI for the given path:
get '/' => sub {
redirect uri_for('/path');
# can be something like: http://localhost:3000/path
};
captures¶
Returns a reference to a copy of "%+", if there are named captures in
the route Regexp.
Named captures are a feature of Perl 5.10, and are not supported in earlier
versions:
get qr{
/ (?<object> user | ticket | comment )
/ (?<action> delete | find )
/ (?<id> \d+ )
/?$
}x
, sub {
my $value_for = captures;
"i don't want to $$value_for{action} the $$value_for{object} $$value_for{id} !"
};
var¶
Provides an accessor for variables shared between filters and route handlers.
Given a key/value pair, it sets a variable:
hook before => sub {
var foo => 42;
};
Later, route handlers and other filters will be able to read that variable:
get '/path' => sub {
my $foo = var 'foo';
...
};
vars¶
Returns the HashRef of all shared variables set during the filter/route chain
with the "var" keyword:
get '/path' => sub {
if (vars->{foo} eq 42) {
...
}
};
warning¶
Logs a warning message through the current logger engine:
warning "This is a warning";
See Dancer2::Core::Role::Logger for details on how to configure where log
messages go.
AUTHOR¶
Dancer Core Developers
COPYRIGHT AND LICENSE¶
This software is copyright (c) 2014 by Alexis Sukrieh.
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.