Provided by: libweb-simple-perl_0.033-1_all 
NAME
Web::Simple - A quick and easy way to build simple web applications
SYNOPSIS
#!/usr/bin/env perl
package HelloWorld;
use Web::Simple;
sub dispatch_request {
GET => sub {
[ 200, [ 'Content-type', 'text/plain' ], [ 'Hello world!' ] ]
},
'' => sub {
[ 405, [ 'Content-type', 'text/plain' ], [ 'Method not allowed' ] ]
}
}
HelloWorld->run_if_script;
If you save this file into your cgi-bin as "hello-world.cgi" and then visit:
http://my.server.name/cgi-bin/hello-world.cgi/
you'll get the "Hello world!" string output to your browser. At the same time this file
will also act as a class module, so you can save it as HelloWorld.pm and use it as-is in
test scripts or other deployment mechanisms.
Note that you should retain the ->run_if_script even if your app is a module, since this
additionally makes it valid as a .psgi file, which can be extremely useful during
development.
For more complex examples and non-CGI deployment, see Web::Simple::Deployment. To get help
with Web::Simple, please connect to the irc.perl.org IRC network and join #web-simple.
DESCRIPTION
The philosophy of Web::Simple is to keep to an absolute bare minimum for everything. It is
not designed to be used for large scale applications; the Catalyst web framework already
works very nicely for that and is a far more mature, well supported piece of software.
However, if you have an application that only does a couple of things, and want to not
have to think about complexities of deployment, then Web::Simple might be just the thing
for you.
The only public interface the Web::Simple module itself provides is an "import" based one:
use Web::Simple 'NameOfApplication';
This sets up your package (in this case "NameOfApplication" is your package) so that it
inherits from Web::Simple::Application and imports strictures, as well as installs a
"PSGI_ENV" constant for convenience, as well as some other subroutines.
Importing strictures will automatically make your code use the "strict" and "warnings"
pragma, so you can skip the usual:
use strict;
use warnings FATAL => 'all';
provided you 'use Web::Simple' at the top of the file. Note that we turn on *fatal*
warnings so if you have any warnings at any point from the file that you did 'use
Web::Simple' in, then your application will die. This is, so far, considered a feature.
When we inherit from Web::Simple::Application we also use Moo, which is the the equivalent
of:
{
package NameOfApplication;
use Moo;
extends 'Web::Simple::Application';
}
So you can use Moo features in your application, such as creating attributes using the
"has" subroutine, etc. Please see the documentation for Moo for more information.
It also exports the following subroutines for use in dispatchers:
response_filter { ... };
redispatch_to '/somewhere';
Finally, import sets
$INC{"NameOfApplication.pm"} = 'Set by "use Web::Simple;" invocation';
so that perl will not attempt to load the application again even if
require NameOfApplication;
is encountered in other code.
One important thing to remember when using
NameOfApplication->run_if_script;
At the end of your app is that this call will create an instance of your app for you
automatically, regardless of context. An easier way to think of this would be if the
method were more verbosely named
NameOfApplication->run_request_if_script_else_turn_coderef_for_psgi;
DISPATCH STRATEGY
Web::Simple despite being straightforward to use, has a powerful system for matching all
sorts of incoming URLs to one or more subroutines. These subroutines can be simple
actions to take for a given URL, or something more complicated, including entire Plack
applications, Plack::Middleware and nested subdispatchers.
Examples
sub dispatch_request {
(
# matches: GET /user/1.htm?show_details=1
# GET /user/1.htm
'GET + /user/* + ?show_details~ + .htm|.html|.xhtml' => sub {
my ($self, $user_id, $show_details) = @_;
...
},
# matches: POST /user?username=frew
# POST /user?username=mst&first_name=matt&last_name=trout
'POST + /user + ?username=&*' => sub {
my ($self, $username, $misc_params) = @_;
...
},
# matches: DELETE /user/1/friend/2
'DELETE + /user/*/friend/*' => sub {
my ($self, $user_id, $friend_id) = @_;
...
},
# matches: PUT /user/1?first_name=Matt&last_name=Trout
'PUT + /user/* + ?first_name~&last_name~' => sub {
my ($self, $user_id, $first_name, $last_name) = @_;
...
},
'/user/*/...' => sub {
my $user_id = $_[1];
(
# matches: PUT /user/1/role/1
'PUT + /role/*' => sub {
my $role_id = $_[1];
...
},
# matches: DELETE /user/1/role/1
'DELETE + /role/*' => sub {
my $role_id = $_[1];
...
},
);
},
);
}
The dispatch cycle
At the beginning of a request, your app's dispatch_request method is called with the PSGI
$env as an argument. You can handle the request entirely in here and return a PSGI
response arrayref if you want:
sub dispatch_request {
my ($self, $env) = @_;
[ 404, [ 'Content-type' => 'text/plain' ], [ 'Amnesia == fail' ] ]
}
However, generally, instead of that, you return a set of route/target pairs:
sub dispatch_request {
my $self = shift;
(
'/' => sub { redispatch_to '/index.html' },
'/user/*' => sub { $self->show_user($_[1]) },
'POST + %*' => 'handle_post',
...
);
}
Well, a sub is a valid PSGI response too (for ultimate streaming and async cleverness). If
you want to return a PSGI sub you have to wrap it into an array ref.
sub dispatch_request {
[ sub {
my $respond = shift;
# This is pure PSGI here, so read perldoc PSGI
} ]
}
If you return a string followed by a subroutine or method name, the string is treated as a
match specification - and if the test is passed, the subroutine is called as a method and
passed any matched arguments (see below for more details).
You can also return a plain subroutine which will be called with just $env - remember that
in this case if you need $self you must close over it.
If you return a normal object, Web::Simple will simply return it upwards on the assumption
that a response_filter (or some arbitrary Plack::Middleware) somewhere will convert it to
something useful. This allows:
sub dispatch_request {
my $self = shift;
(
'.html' => sub { response_filter { $self->render_zoom($_[0]) } },
'/user/*' => sub { $self->users->get($_[1]) },
);
}
An alternative to using string + suborutine to declare a route is to use the sub prototype
-
sub dispatch_request {
my $self = shift;
(
sub (.html) { response_filter { $self->render_zoom($_[0]) } },
sub (/user/) { $self->users->get($_[1]) },
$self->can('handle_post'), # if declared as 'sub handle_post (...) {'
)
}
This can be useful sugar, especially if you want to keep method-based dispatchers' route
specifications on the methods.
to render a user object to HTML, if there is an incoming URL such as:
http://myweb.org/user/111.html
This works because as we descend down the dispachers, we first match "sub (.html)", which
adds a "response_filter" (basically a specialized routine that follows the
Plack::Middleware specification), and then later we also match "sub (/user/*)" which gets
a user and returns that as the response. This user object 'bubbles up' through all the
wrapping middleware until it hits the "response_filter" we defined, after which the return
is converted to a true html response.
However, two types of objects are treated specially - a "Plack::Component" object will
have its "to_app" method called and be used as a dispatcher:
sub dispatch_request {
my $self = shift;
(
'/static/...' => sub { Plack::App::File->new(...) },
...
);
}
A Plack::Middleware object will be used as a filter for the rest of the dispatch being
returned into:
## responds to /admin/track_usage AND /admin/delete_accounts
sub dispatch_request {
my $self = shift;
(
'/admin/**' => sub {
Plack::Middleware::Session->new(%opts);
},
'/admin/track_usage' => sub {
## something that needs a session
},
'/admin/delete_accounts' => sub {
## something else that needs a session
},
);
}
Note that this is for the dispatch being returned to, so if you want to provide it inline
you need to do:
## ALSO responds to /admin/track_usage AND /admin/delete_accounts
sub dispatch_request {
my $self = shift;
(
'/admin/...' => sub {
(
sub {
Plack::Middleware::Session->new(%opts);
},
'/track_usage' => sub {
## something that needs a session
},
'/delete_accounts' => sub {
## something else that needs a session
},
);
}
);
}
And that's it - but remember that all this happens recursively - it's dispatchers all the
way down. A URL incoming pattern will run all matching dispatchers and then hit all added
filters or Plack::Middleware.
Web::Simple match specifications
Method matches
'GET' => sub {
A match specification beginning with a capital letter matches HTTP requests with that
request method.
Path matches
'/login' => sub {
A match specification beginning with a / is a path match. In the simplest case it matches
a specific path. To match a path with a wildcard part, you can do:
'/user/*' => sub {
$self->handle_user($_[1])
This will match /user/<anything> where <anything> does not include a literal / character.
The matched part becomes part of the match arguments. You can also match more than one
part:
'/user/*/*' => sub {
my ($self, $user_1, $user_2) = @_;
'/domain/*/user/*' => sub {
my ($self, $domain, $user) = @_;
and so on. To match an arbitrary number of parts, use "**":
'/page/**' => sub {
my ($self, $match) = @_;
This will result in a single element for the entire match. Note that you can do
'/page/**/edit' => sub {
to match an arbitrary number of parts up to but not including some final part.
Note: Since Web::Simple handles a concept of file extensions, "*" and "**" matchers will
not by default match things after a final dot, and this can be modified by using "*.*" and
"**.*" in the final position, e.g.:
/one/* matches /one/two.three and captures "two"
/one/*.* matches /one/two.three and captures "two.three"
/** matches /one/two.three and captures "one/two"
/**.* matches /one/two.three and captures "one/two.three"
Finally,
'/foo/...' => sub {
Will match "/foo/" on the beginning of the path and strip it. This is designed to be used
to construct nested dispatch structures, but can also prove useful for having e.g. an
optional language specification at the start of a path.
Note that the '...' is a "maybe something here, maybe not" so the above specification will
match like this:
/foo # no match
/foo/ # match and strip path to '/'
/foo/bar/baz # match and strip path to '/bar/baz'
Almost the same,
'/foo...' => sub {
Will match on "/foo/bar/baz", but also include "/foo". Otherwise it operates the same way
as "/foo/...".
/foo # match and strip path to ''
/foo/ # match and strip path to '/'
/foo/bar/baz # match and strip path to '/bar/baz'
Please note the difference between "sub(/foo/...)" and "sub(/foo...)". In the first case,
this is expecting to find something after "/foo" (and fails to match if nothing is found),
while in the second case we can match both "/foo" and "/foo/more/to/come". The following
are roughly the same:
'/foo' => sub { 'I match /foo' },
'/foo/...' => sub {
(
'/bar' => sub { 'I match /foo/bar' },
'/*' => sub { 'I match /foo/{id}' },
);
}
Versus
'/foo...' => sub {
(
'~' => sub { 'I match /foo' },
'/bar' => sub { 'I match /foo/bar' },
'/*' => sub { 'I match /foo/{id}' },
);
}
You may prefer the latter example should you wish to take advantage of subdispatchers to
scope common activities. For example:
'/user...' => sub {
my $user_rs = $schema->resultset('User');
(
'~' => sub { $user_rs },
'/*' => sub { $user_rs->find($_[1]) },
);
}
You should note the special case path match "sub (~)" which is only meaningful when it is
contained in this type of path match. It matches to an empty path.
Naming your patch matches
Any "*", "**", "*.*", or "**.*" match can be followed with ":name" to make it into a named
match, so:
'/*:one/*:two/*:three/*:four' => sub {
"I match /1/2/3/4 capturing { one => 1, two => 2, three => 3, four => 4 }"
}
'/**.*:allofit' => sub {
"I match anything capturing { allofit => \$whole_path }"
}
In the specific case of a simple single-* match, the * may be omitted, to allow you to
write:
'/:one/:two/:three/:four' => sub {
"I match /1/2/3/4 capturing { one => 1, two => 2, three => 3, four => 4 }"
}
"/foo" and "/foo/" are different specs
As you may have noticed with the difference between '/foo/...' and '/foo...', trailing
slashes in path specs are significant. This is intentional and necessary to retain the
ability to use relative links on websites. Let's demonstrate on this link:
<a href="bar">bar</a>
If the user loads the url "/foo/" and clicks on this link, they will be sent to
"/foo/bar". However when they are on the url "/foo" and click this link, then they will be
sent to "/bar".
This makes it necessary to be explicit about the trailing slash.
Extension matches
'.html' => sub {
will match .html from the path (assuming the subroutine itself returns something, of
course). This is normally used for rendering - e.g.:
'.html' => sub {
response_filter { $self->render_html($_[1]) }
}
Additionally,
'.*' => sub {
will match any extension and supplies the extension as a match argument.
Query and body parameter matches
Query and body parameters can be match via
'?<param spec>' => sub { # match URI query
'%<param spec>' => sub { # match body params
The body spec will match if the request content is either
application/x-www-form-urlencoded or multipart/form-data - the latter of which is required
for uploads - see below.
The param spec is elements of one of the following forms:
param~ # optional parameter
param= # required parameter
@param~ # optional multiple parameter
@param= # required multiple parameter
:param~ # optional parameter in hashref
:param= # required parameter in hashref
:@param~ # optional multiple in hashref
:@param= # required multiple in hashref
* # include all other parameters in hashref
@* # include all other parameters as multiple in hashref
separated by the "&" character. The arguments added to the request are one per non-":"/"*"
parameter (scalar for normal, arrayref for multiple), plus if any ":"/"*" specs exist a
hashref containing those values. If a parameter has no value, i.e. appears as '?foo&', a
value of 1 will be captured.
Please note that if you specify a multiple type parameter match, you are ensured of
getting an arrayref for the value, EVEN if the current incoming request has only one
value. However if a parameter is specified as single and multiple values are found, the
last one will be used.
For example to match a "page" parameter with an optional "order_by" parameter one would
write:
'?page=&order_by~' => sub {
my ($self, $page, $order_by) = @_;
return unless $page =~ /^\d+$/;
$order_by ||= 'id';
response_filter {
$_[1]->search_rs({}, { page => $page, order_by => $order_by });
}
}
to implement paging and ordering against a DBIx::Class::ResultSet object.
Another Example: To get all parameters as a hashref of arrayrefs, write:
'?@*' => sub {
my ($self, $params) = @_;
...
To get two parameters as a hashref, write:
'?:user~&:domain~' => sub {
my ($self, $params) = @_; # params contains only 'user' and 'domain' keys
You can also mix these, so:
'?foo=&@bar~&:coffee=&@*' => sub {
my ($self, $foo, $bar, $params) = @_;
where $bar is an arrayref (possibly an empty one), and $params contains arrayref values
for all parameters not mentioned and a scalar value for the 'coffee' parameter.
Note, in the case where you combine arrayref, single parameter and named hashref style,
the arrayref and single parameters will appear in @_ in the order you defined them in the
prototype, but all hashrefs will merge into a single $params, as in the example above.
Upload matches
'*foo=' => sub { # param specifier can be anything valid for query or body
The upload match system functions exactly like a query/body match, except that the values
returned (if any) are "Web::Dispatch::Upload" objects.
Note that this match type will succeed in two circumstances where you might not expect it
to - first, when the field exists but is not an upload field and second, when the field
exists but the form is not an upload form (i.e. content type
"application/x-www-form-urlencoded" rather than "multipart/form-data"). In either of these
cases, what you'll get back is a "Web::Dispatch::NotAnUpload" object, which will "die"
with an error pointing out the problem if you try and use it. To be sure you have a real
upload object, call
$upload->is_upload # returns 1 on a valid upload, 0 on a non-upload field
and to get the reason why such an object is not an upload, call
$upload->reason # returns a reason or '' on a valid upload.
Other than these two methods, the upload object provides the same interface as
Plack::Request::Upload with the addition of a stringify to the temporary filename to make
copying it somewhere else easier to handle.
Combining matches
Matches may be combined with the + character - e.g.
'GET + /user/*' => sub {
to create an AND match. They may also be combined with the | character - e.g.
'GET|POST' => sub {
to create an OR match. Matches can be nested with () - e.g.
'(GET|POST + /user/*)' => sub {
and negated with ! - e.g.
'!/user/foo + /user/*' => sub {
! binds to the immediate rightmost match specification, so if you want to negate a
combination you will need to use
'!(POST|PUT|DELETE)' => sub {
and | binds tighter than +, so
'(GET|POST) + /user/*' => sub {
and
'GET|POST + /user/*' => sub {
are equivalent, but
'(GET + /admin/...) | (POST + /admin/...)' => sub {
and
'GET + /admin/... | POST + /admin/...' => sub {
are not - the latter is equivalent to
'GET + (/admin/...|POST) + /admin/...' => sub {
which will never match!
Whitespace
Note that for legibility you are permitted to use whitespace:
'GET + /user/*' => sub {
but it will be ignored. This is because the perl parser strips whitespace from subroutine
prototypes, so this is equivalent to
'GET+/user/*' => sub {
Accessing parameters via %_
If your dispatch specification causes your dispatch subroutine to receive a hash reference
as its first argument, the contained named parameters will be accessible via %_.
This can be used to access your path matches, if they are named:
'GET + /foo/:path_part' => sub {
[ 200,
['Content-type' => 'text/plain'],
["We are in $_{path_part}"],
];
}
Or, if your first argument would be a hash reference containing named query parameters:
'GET + /foo + ?:some_param=' => sub {
[ 200,
['Content-type' => 'text/plain'],
["We received $_{some_param} as parameter"],
];
}
Of course this also works when all you are doing is slurping the whole set of parameters
by their name:
'GET + /foo + ?*' => sub {
[ 200,
['Content-type' => 'text/plain'],
[exists($_{foo}) ? "Received a foo: $_{foo}" : "No foo!"],
],
}
Note that only the first hash reference will be available via %_. If you receive
additional hash references, you will need to access them as usual.
Accessing the PSGI env hash
In some cases you may wish to get the raw PSGI env hash - to do this, you can either use a
plain sub:
sub {
my ($env) = @_;
...
}
or use the "PSGI_ENV" constant exported to retrieve it from @_:
'GET + /foo + ?some_param=' => sub {
my $param = $_[1];
my $env = $_[PSGI_ENV];
}
but note that if you're trying to add a middleware, you should simply use Web::Simple's
direct support for doing so.
EXPORTED SUBROUTINES
response_filter
response_filter {
# Hide errors from the user because we hates them, preciousss
if (ref($_[0]) eq 'ARRAY' && $_[0]->[0] == 500) {
$_[0] = [ 200, @{$_[0]}[1..$#{$_[0]}] ];
}
return $_[0];
};
The response_filter subroutine is designed for use inside dispatch subroutines.
It creates and returns a special dispatcher that always matches, and calls the block
passed to it as a filter on the result of running the rest of the current dispatch chain.
Thus the filter above runs further dispatch as normal, but if the result of dispatch is a
500 (Internal Server Error) response, changes this to a 200 (OK) response without altering
the headers or body.
redispatch_to
redispatch_to '/other/url';
The redispatch_to subroutine is designed for use inside dispatch subroutines.
It creates and returns a special dispatcher that always matches, and instead of continuing
dispatch re-delegates it to the start of the dispatch process, but with the path of the
request altered to the supplied URL.
Thus if you receive a POST to "/some/url" and return a redispatch to "/other/url", the
dispatch behaviour will be exactly as if the same POST request had been made to
"/other/url" instead.
Note, this is not the same as returning an HTTP 3xx redirect as a response; rather it is a
much more efficient internal process.
CHANGES BETWEEN RELEASES
Changes between 0.004 and 0.005
• dispatch {} replaced by declaring a dispatch_request method
dispatch {} has gone away - instead, you write:
sub dispatch_request {
my $self = shift;
(
'GET /foo/' => sub { ... },
...
);
}
Note that this method is still returning the dispatch code - just like "dispatch" did.
Also note that you need the "my $self = shift" since the magic $self variable went
away.
• the magic $self variable went away.
Just add "my $self = shift;" while writing your "sub dispatch_request {" like a normal
perl method.
• subdispatch deleted - all dispatchers can now subdispatch
In earlier releases you needed to write:
subdispatch sub (/foo/...) {
...
[
sub (GET /bar/) { ... },
...
]
}
As of 0.005, you can instead write simply:
sub (/foo/...) {
...
(
sub (GET /bar/) { ... },
...
)
}
Changes since Antiquated Perl
• filter_response renamed to response_filter
This is a pure rename; a global search and replace should fix it.
• dispatch [] changed to dispatch {}
Simply changing
dispatch [ sub(...) { ... }, ... ];
to
dispatch { sub(...) { ... }, ... };
should work fine.
DEVELOPMENT HISTORY
Web::Simple was originally written to form part of my Antiquated Perl talk for Italian
Perl Workshop 2009, but in writing the bloggery example I realised that having a bare
minimum system for writing web applications that doesn't drive me insane was rather nice
and decided to spend my attempt at nanowrimo for 2009 improving and documenting it to the
point where others could use it.
The Antiquated Perl talk can be found at
<http://www.shadowcat.co.uk/archive/conference-video/> and the slides are reproduced in
this distribution under Web::Simple::AntiquatedPerl.
COMMUNITY AND SUPPORT
IRC channel
irc.perl.org #web-simple
No mailing list yet
Because mst's non-work email is a bombsite so he'd never read it anyway.
Git repository
Gitweb is on http://git.shadowcat.co.uk/ and the clone URL is:
git clone git://git.shadowcat.co.uk/catagits/Web-Simple.git
AUTHOR
Matt S. Trout (mst) <mst@shadowcat.co.uk>
CONTRIBUTORS
Devin Austin (dhoss) <dhoss@cpan.org>
Arthur Axel 'fREW' Schmidt <frioux@gmail.com>
gregor herrmann (gregoa) <gregoa@debian.org>
John Napiorkowski (jnap) <jjn1056@yahoo.com>
Josh McMichael <jmcmicha@linus222.gsc.wustl.edu>
Justin Hunter (arcanez) <justin.d.hunter@gmail.com>
Kjetil Kjernsmo <kjetil@kjernsmo.net>
markie <markie@nulletch64.dreamhost.com>
Christian Walde (Mithaldu) <walde.christian@googlemail.com>
nperez <nperez@cpan.org>
Robin Edwards <robin.ge@gmail.com>
Andrew Rodland (hobbs) <andrew@cleverdomain.org>
Robert Sedlacek (phaylon) <r.sedlacek@shadowcat.co.uk>
Hakim Cassimally (osfameron) <osfameron@cpan.org>
Karen Etheridge (ether) <ether@cpan.org>
COPYRIGHT
Copyright (c) 2011 the Web::Simple "AUTHOR" and "CONTRIBUTORS" as listed above.
LICENSE
This library is free software and may be distributed under the same terms as perl itself.