Web::Machine::Resource(3)

User Contributed Perl Documentation

Web::Machine::Resource(3)

NAME¶

Web::Machine::Resource - A base resource class

VERSION¶

version 0.17

SYNOPSIS¶

  package HelloWorld::Resource;
  use strict;
  use warnings;
  use parent 'Web::Machine::Resource';
  sub content_types_provided { [{ 'text/html' => 'to_html' }] }
  sub to_html {
      q{<html>
          <head>
              <title>Hello World Resource</title>
          </head>
          <body>
              <h1>Hello World</h1>
          </body>
       </html>}
  }

DESCRIPTION¶

This is the core representation of the web resource in Web::Machine. It is this object which is interrogated through the state machine. It is important not to think of this as an instance of a single object, but as a web representation of a resource: there is a big difference.

For now I am keeping the documentation short, but much more needs to be written here. Below you will find a description of each method this object provides and what is expected of it. Your resource classes should extend the base Web::Machine::Resource class, overriding its methods as necessary. Sane defaults are provided for most methods, but you will want to create a "content_types_provided" method, as without this your resource will not be able to return any useful content.

The documentation was lovingly stolen from the ruby port of webmachine.

METHODS¶

Keep in mind that the methods may be called more than once per request, so your implementations should be idempotent.

init( \%args )

This method is called right after the object is blessed and it is passed a reference to the original %args that were given to the constructor. By default, these will include "request" (Plack::Request) and "response" (Plack::Response) arguments.

If your resource is instantiated via Web::Machine then the contents of its "resource_args" parameter will be appended to the Web::Machine::Resource constructor arguments and made available to "init":

    use strict;
    use warnings;
    use Web::Machine;
    {
        package HelloWorld::Resource;
        use strict;
        use warnings;
        use JSON::XS qw[ encode_json ];
        use parent 'Web::Machine::Resource';
        sub init {
            my $self = shift;
            my $args = shift;
            # Plack::Request
            # my $request = $args->{request};
            # Plack::Response
            # my $response = $args->{response};
            $self->{json}
                = exists $args->{json}
                ? $args->{json}
                : {};
        }
        sub content_types_provided { [ { 'application/json' => 'to_json' } ] }
        sub to_json {
            my $self = shift;
            encode_json( $self->{json} );
        }
    }
    Web::Machine->new(
        resource      => 'HelloWorld::Resource',
        resource_args => [
            json => {
                message => 'Hello World!',
            },
        ],
    )->to_app;

"request"

Returns the Plack::Request (or subclass) request object for the current request.

"response"

Returns the Plack::Response (or subclass) response object for the current request.

"resource_exists"

Does the resource exist?

Returning a false value will result in a '404 Not Found' response.

Defaults to true.

"service_available"

Is the resource available?

Returning a false value will result in a '503 Service Not Available' response.

Defaults to true.

If the resource is only temporarily not available, add a 'Retry-After' response header in the body of the method.

"is_authorized ( ?$authorization_header )"

Is the client or request authorized?

Parameter $authorization_header is the contents of the 'Authorization' header sent by the client, if present.

Returning anything other than 1 will result in a '401 Unauthorized' response. If a string is returned, it will be used as the value in the 'WWW-Authenticate' response header, which can also be set manually.

Defaults to true.

"forbidden"

Is the request or client forbidden?

Returning a true value will result in a '403 Forbidden' response.

Defaults to false.

"allow_missing_post"

If the resource accepts POST requests to nonexistent resources, then this should return true.

Defaults to false.

"malformed_request"

If the request is malformed, this should return true, which will result in a '400 Malformed Request' response.

Defaults to false.

uri_too_long( $uri )

If the URI is too long to be processed, this should return true, which will result in a '414 Request URI Too Long' response.

Defaults to false.

known_content_type( $content_type )

If the 'Content-Type' on PUT or POST is unknown, this should return false, which will result in a '415 Unsupported Media Type' response.

The value of $content_type is derived from the Plack::Request object and will therefore be an instance of the HTTP::Headers::ActionPack::MediaType class.

Defaults to true.

valid_content_headers( $content_headers )

Parameter $content_header is a HASH ref of the Request headers that begin with prefix 'Content-'. It will contain instances of HTTP::Headers::ActionPack::MediaType, HTTP::Headers::ActionPack::MediaTypeList and HTTP::Headers::ActionPack::PriorityList based on the headers included. See HTTP::Headers::ActionPack for details of the mappings.

If the request includes any invalid Content-* headers, this should return false, which will result in a '501 Not Implemented' response.

Defaults to true.

valid_entity_length( $length )

Parameter $length is a number indicating the size of the request body.

If the entity length on PUT or POST is invalid, this should return false, which will result in a '413 Request Entity Too Large' response.

Defaults to true.

"options"

If the OPTIONS method is supported and is used, this method should return a HASH ref of headers that should appear in the response.

Defaults to {}.

"allowed_methods"

HTTP methods that are allowed on this resource. This must return an ARRAY ref of strings in all capitals.

Defaults to "['GET','HEAD']".

"known_methods"

HTTP methods that are known to the resource. Like "allowed_methods", this must return an ARRAY ref of strings in all capitals. One could override this callback to allow additional methods, e.g. WebDAV.

Default includes all standard HTTP methods, "['GET', 'HEAD', 'POST', 'PUT', 'DELETE', 'TRACE', 'CONNECT', 'OPTIONS']".

"delete_resource"

This method is called when a DELETE request should be enacted, and should return true if the deletion succeeded.

Defaults to false.

"delete_completed"

This method is called after a successful call to "delete_resource" and should return false if the deletion was accepted but cannot yet be guaranteed to have finished.

Defaults to true.

"post_is_create"

If POST requests should be treated as a request to put content into a (potentially new) resource as opposed to a generic submission for processing, then this method should return true. If it does return true, then "create_path" will be called and the rest of the request will be treated much like a PUT to the path returned by that call.

Default is false.

"create_path"

This will be called on a POST request if post_is_create? returns true. The path returned should be a valid URI part following the dispatcher prefix.

"create_path_after_handler"

This changes the behavior of "create_path" so that it will fire after the content handler has processed the request body. This allows the creation of paths that are more tightly tied to the newly created entity.

Default is false.

"base_uri"

This will be called after "create_path" but before setting the Location response header, and is used to determine the root URI of the new resource.

Default is nil, which uses the URI of the request as the base.

"process_post"

If post_is_create? returns false, then this will be called to process any POST request. If it succeeds, it should return true.

"content_types_provided"

This should return an ARRAY of HASH ref pairs where the key is the name of the media type and the value is a CODE ref (or name of a method) which can provide a resource representation in that media type.

For example, if a client request includes an 'Accept' header with a value that does not appear as a first element in any of the return pairs, then a '406 Not Acceptable' will be sent.

The order of HASH ref pairs in the ARRAY is important. If no specific content type is requested (the client does not send an "Accept" header) then the first content type in the ARRAY will be used as the default.

Default is an empty ARRAY ref.

"content_types_accepted"

Similarly to content_types_provided, this should return an ARRAY of mediatype/handler pairs, except that it is for incoming resource representations -- for example, PUT requests. Handler functions usually want to use "$request->body" to access the incoming entity.

"charsets_provided"

This specifies the charsets that your resource support. Returning a value from this method enables content negotiation based on the client's Accept-Charset header.

The return value from this method must be an ARRAY ref. Each member of that array can be either a string or a HASH ref pair value. If the member is a string, it must be a valid character set name for the Encode module. Web::Machine will call encode() on the body using this character set if you set a body.

  sub charsets_provided {
      return [ qw( UTF-8 ISO-8859-1 shiftjis ) ];
  }

If you return a HASHREF pair, the key must be a character set name and the value must be a CODE ref. This CODE ref will be called as a method on the resource object. It will receive a single parameter, a string to be encoded. It is expected to return a scalar containing bytes, not characters. This will be used to encode the body you provide.

  sub charsets_provided {
      return [
          {
              'UTF-8' => sub {
                  my $self   = shift;
                  my $string = shift;
                  return make_some_bytes($string),;
              },
          },
          {
              'ISO-8859-1' => sub {
                  my $self   = shift;
                  my $string = shift;
                  return strip_non_ascii($string),;
              },
          },
      ];
  }

The character set name will be appended to the Content-Type header returned the client.

If a client specifies the same preference for two or more character sets that your resource provides, then Web::Machine chooses the first character set in the returned ARRAY ref.

CAVEAT: Note that currently "Web::Machine" does not support the use of encodings when the body is returned as a CODE ref. This is a bug to be remedied in the future.

Default is an empty list.

"default_charset"

If the client does not provide an Accept-Charset header, this sub is called to provide a default charset. The return value must be either a string or a hashref consisting of a single pair, where the key is a character set name and the value is a subroutine.

This works just like the charsets_provided() method, except that you can only return a single value.

"languages_provided"

This should return a list of language tags provided by the resource. Default is the empty Array, in which the content is in no specific language.

"encodings_provided"

This should return a HASH of encodings mapped to encoding methods for Content-Encodings your resource wants to provide. The encoding will be applied to the response body automatically by "Web::Machine".

CAVEAT: Note that currently "Web::Machine" does not support the use of encodings when the body is returned as a CODE ref. This is a bug to be remedied in the future.

Default includes only the 'identity' encoding.

"variances"

If this method is implemented, it should return a list of strings with header names that should be included in a given response's Vary header. The standard content negotiation headers (Accept, Accept-Encoding, Accept-Charset, Accept-Language) do not need to be specified here as "Web::Machine" will add the correct elements of those automatically depending on resource behavior.

Default is [].

"is_conflict"

If this returns true, the client will receive a '409 Conflict' response. This is only called for PUT requests.

Default is false.

"multiple_choices"

If this returns true, then it is assumed that multiple representations of the response are possible and a single one cannot be automatically chosen, so a 300 Multiple Choices will be sent instead of a 200.

Default is false.

"previously_existed"

If this resource is known to have existed previously, this method should return true.

Default is false.

"moved_permanently"

If this resource has moved to a new location permanently, this method should return the new location as a String or URI.

Default is to return false.

"moved_temporarily"

If this resource has moved to a new location temporarily, this method should return the new location as a String or URI.

Default is to return false.

"last_modified"

This method should return the last modified date/time of the resource which will be added as the Last-Modified header in the response and used in negotiating conditional requests. This should be in the form of an instance of HTTP::Headers::ActionPack::DateHeader.

Default is undef.

"expires"

If the resource expires, this method should return the date/time it expires. This should be in the form of an instance of HTTP::Headers::ActionPack::DateHeader.

Default is nil.

"generate_etag"

If this returns a value, it will be used as the value of the ETag header and for comparison in conditional requests.

Default is undef.

finish_request( $metadata )

This method is called just before the final response is constructed and sent. It is passed the collected $metadata from the FSM, which may or may not have information in it.

The return value is ignored, so any effect of this method must be by modifying the response.

SUPPORT¶

bugs may be submitted through <https://github.com/houseabsolute/webmachine-perl/issues>.

AUTHORS¶

Stevan Little <stevan@cpan.org>
Dave Rolsky <autarch@urth.org>

COPYRIGHT AND LICENCE¶

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

2024-03-04

perl v5.40.0

Source file:	Web::Machine::Resource.3pm.en.gz (from perl-Web-Machine 0.17-3.2)
Source last updated:	2024-03-04T15:40:45Z
Converted to HTML:	2024-12-21T01:58:08Z