NAME

       Catalyst::View::JSON - JSON view for your data

SYNOPSIS

         # lib/MyApp/View/JSON.pm
         package MyApp::View::JSON;
         use base qw( Catalyst::View::JSON );
         1;

         # configure in lib/MyApp.pm
         MyApp->config({
             ...
             'View::JSON' => {
                 allow_callback  => 1,    # defaults to 0
                 callback_param  => 'cb', # defaults to 'callback'
                 expose_stash    => [ qw(foo bar) ], # defaults to everything
             },
         });

         sub hello : Local {
             my($self, $c) = @_;
             $c->stash->{message} = 'Hello World!';
             $c->forward('View::JSON');
         }

DESCRIPTION

       Catalyst::View::JSON is a Catalyst View handler that returns stash data in JSON format.

CONFIG VARIABLES

       allow_callback
           Flag to allow callbacks by adding "callback=function". Defaults to 0 (doesn't allow
           callbacks). See "CALLBACKS" for details.

       callback_param
           Name of URI parameter to specify JSON callback function name. Defaults to "callback".
           Only effective when "allow_callback" is turned on.

       expose_stash
           Scalar, List or regular expression object, to specify which stash keys are exposed as
           a JSON response. Defaults to everything. Examples configuration:

             # use 'json_data' value as a data to return
             expose_stash => 'json_data',

             # only exposes keys 'foo' and 'bar'
             expose_stash => [ qw( foo bar ) ],

             # only exposes keys that matches with /^json_/
             expose_stash => qr/^json_/,

           Suppose you have data structure of the following.

             $c->stash->{foo} = [ 1, 2 ];
             $c->stash->{bar} = [ 3, 4 ];

           By default, this view will return:

             {"foo":[1,2],"bar":2}

           When you set "expose_stash => [ 'foo' ]", it'll return

             {"foo":[1,2]}

           and in the case of "expose_stash => 'foo'", it'll just return

             [1,2]

           instead of the whole object (hashref in perl). This option will be useful when you
           share the method with different views (e.g. TT) and don't want to expose non-
           irrelevant stash variables as in JSON.

       json_driver
             json_driver: JSON::Syck

           By default this plugin uses JSON to encode the object, but you can switch to the other
           drivers like JSON::Syck, whichever JSON::Any supports.

       no_x_json_header
             no_x_json_header: 1

           By default this plugin sets X-JSON header if the requested client is a Prototype.js
           with X-JSON support. By setting 1, you can opt-out this behavior so that you can do
           eval() by your own. Defaults to 0.

OVERRIDING JSON ENCODER

       By default it uses JSON::Any to serialize perl data strucuture into JSON data format. If
       you want to avoid this and encode with your own encoder (like passing options to JSON::XS
       etc.), you can implement "encode_json" method in your View class.

         package MyApp::View::JSON;
         use base qw( Catalyst::View::JSON );

         use JSON::XS ();

         sub encode_json {
             my($self, $c, $data) = @_;
             my $encoder = JSON::XS->new->ascii->pretty->allow_nonref;
             $encoder->encode($data);
         }

         1;

ENCODINGS

       Due to the browser gotchas like those of Safari and Opera, sometimes you have to specify a
       valid charset value in the response's Content-Type header, e.g. "text/javascript;
       charset=utf-8".

       Catalyst::View::JSON comes with the configuration variable "encoding" which defaults to
       utf-8. You can change it via "YourApp->config" or even runtime, using "component".

         $c->component('View::JSON')->encoding('euc-jp');

       This assumes you set your stash data in raw euc-jp bytes, or Unicode flagged variable. In
       case of Unicode flagged variable, Catalyst::View::JSON automatically encodes the data into
       your "encoding" value (euc-jp in this case) before emitting the data to the browser.

       Another option would be to use JavaScript-UCS as an encoding (and pass Unicode flagged
       string to the stash). That way all non-ASCII characters in the output JSON will be
       automatically encoded to JavaScript Unicode encoding like \uXXXX. You have to install
       Encode::JavaScript::UCS to use the encoding.

CALLBACKS

       By default it returns raw JSON data so your JavaScript app can deal with using
       XMLHttpRequest calls. Adding callbacks (JSONP) to the API gives more flexibility to the
       end users of the API: overcome the cross-domain restrictions of XMLHttpRequest. It can be
       done by appending script node with dynamic DOM manipulation, and associate callback
       handler to the returned data.

       For example, suppose you have the following code.

         sub end : Private {
             my($self, $c) = @_;
             if ($c->req->param('output') eq 'json') {
                 $c->forward('View::JSON');
             } else {
                 ...
             }
         }

       "/foo/bar?output=json" will just return the data set in "$c->stash" as JSON format, like:

         { result: "foo", message: "Hello" }

       but "/foo/bar?output=json&callback=handle_result" will give you:

         handle_result({ result: "foo", message: "Hello" });

       and you can write a custom "handle_result" function to handle the returned data
       asynchronously.

       The valid characters you can use in the callback function are

         [a-zA-Z0-9\.\_\[\]]

       but you can customize the behaviour by overriding the "validate_callback_param" method in
       your View::JSON class.

       See <http://developer.yahoo.net/common/json.html> and
       <http://ajaxian.com/archives/jsonp-json-with-padding> for more about JSONP.

INTEROPERABILITY

       JSON use is still developing and has not been standardized. This section provides some
       notes on various libraries.

       Dojo Toolkit: Setting dojo.io.bind's mimetype to 'text/json' in the JavaScript request
       will instruct dojo.io.bind to expect JSON data in the response body and auto-eval it. Dojo
       ignores the server response Content-Type. This works transparently with
       Catalyst::View::JSON.

       Prototype.js: prototype.js will auto-eval JSON data that is returned in the custom X-JSON
       header. The reason given for this is to allow a separate HTML fragment in the response
       body, however this of limited use because IE 6 has a max header length that will cause the
       JSON evaluation to silently fail when reached. The recommened approach is to use
       Catalyst::View::JSON which will JSON format all the response data and return it in the
       response body.

       In at least prototype 1.5.0 rc0 and above, prototype.js will send the X-Prototype-Version
       header. If this is encountered, a JavaScript eval will be returned in the X-JSON resonse
       header to automatically eval the response body, unless you set no_x_json_header to 1. If
       your version of prototype does not send this header, you can manually eval the response
       body using the following JavaScript:

         evalJSON: function(request) {
           try {
             return eval('(' + request.responseText + ')');
           } catch (e) {}
         }
         // elsewhere
         var json = this.evalJSON(request);

SECURITY CONSIDERATION

       Catalyst::View::JSON makes the data available as a (sort of) JavaScript to the client, so
       you might want to be careful about the security of your data.

   Use callbacks only for public data
       When you enable callbacks (JSONP) by setting "allow_callbacks", all your JSON data will be
       available cross-site. This means embedding private data of logged-in user to JSON is
       considered bad.

         # MyApp.yaml
         View::JSON:
           allow_callbacks: 1

         sub foo : Local {
             my($self, $c) = @_;
             $c->stash->{address} = $c->user->street_address; # BAD
             $c->forward('View::JSON');
         }

       If you want to enable callbacks in a controller (for public API) and disable in another,
       you need to create two different View classes, like MyApp::View::JSON and
       MyApp::View::JSONP, because "allow_callbacks" is a static configuration of the View::JSON
       class.

       See <http://ajaxian.com/archives/gmail-csrf-security-flaw> for more.

   Avoid valid cross-site JSON requests
       Even if you disable the callbacks, the nature of JavaScript still has a possiblity to
       access private JSON data cross-site, by overriding Array constructor "[]".

         # MyApp.yaml
         View::JSON:
           expose_stash: json

         sub foo : Local {
             my($self, $c) = @_;
             $c->stash->{json} = [ $c->user->street_address ]; # BAD
             $c->forward('View::JSON');
         }

       When you return logged-in user's private data to the response JSON, you might want to
       disable GET requests (because script tag invokes GET requests), or include a random digest
       string and validate it.

       See
       <http://jeremiahgrossman.blogspot.com/2006/01/advanced-web-attack-techniques-using.html>
       for more.

AUTHOR

       Tatsuhiko Miyagawa <miyagawa@bulknews.net>

LICENSE

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

CONTRIBUTORS

       Following people has been contributing patches, bug reports and suggestions for the
       improvement of Catalyst::View::JSON.

       John Wang kazeburo Daisuke Murase Jun Kuriyama Tomas Doran

SEE ALSO

       Catalyst, JSON, Encode::JavaScript::UCS

       <http://www.prototypejs.org/learn/json> <http://docs.jquery.com/Ajax/jQuery.getJSON>
       <http://manual.dojotoolkit.org/json.html> <http://developer.yahoo.com/yui/json/>