NAME

WebService::GData::Base - core read/write methods for google data API v2.

VERSION

0.01

SYNOPSIS

        use WebService::GData::Base;

    #create an object that only has read access
        my $base = new WebService::GData::Base();

        #get a feed response from google
        #by default the alt is set to 'json',it will change the JSON response to a perl object.
        my $ret  = $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');
        my $feed = $ret->{feed};

        #give write access with a $auth object that you created somewhere
        $base->auth($auth);

        #now you can (url are here for examples!)

        #get contents even hidden for public access
        my $ret = $base->get('http://gdata.youtube.com/feeds/api/users/default/playlists');

        #create a new entry with application/x-www-form-urlencoded content-type
        my $ret = $base->post('http://gdata.youtube.com/feeds/api/users/default/playlists',$content);

        #delete
        my $ret = $base->delete('http://gdata.youtube.com/feeds/api/users/playlist/'.$someid);

        #the same as post but the content is decorated with the xml entry basic tags
        #the content type is application/atom+xml; charset=UTF-8
        my $ret = $base->insert($uri,$content,$callback);

        #does a put to the server. The content is decorated with the xml entry basic tags
        #the content type is application/atom+xml; charset=UTF-8
        my $ret = $base->update($uri,$content,$callback);

        #now the query will have the following query string: ?alt=json-c&v=2&prettyprint=false&strict=true
        $base->query->alt('json-c')->prettyprint('false');

    #overwrite WebService::GData::Query with youtube query parameters
        $base->query(new WebService::GData::YouTube::Query);

        #now the query will have the following query string: ?alt=json&v=2&prettyprint=true&strict=true&safeSearch=none
        $base->query->safeSearch('none');

DESCRIPTION

inherits from WebService::GData;

This package grants you access to the main read/write methods available for the google data APIs by wrapping LWP methods.

You gain access to:

get,post,insert,update,delete.

These methods set extra headers necessary to authenticate or extra headers required by the service you want to use.

This package should be inherited by services (youtube,analytics) to offer higher level of abstraction.

Every request (get,post,insert,update,delete) will throw (well, die) a WebService::GData::Error in case of failure.

It is therefore recommanded to enclose your code in eval blocks to catch and handle the error as you see fit.

The google data based APIs offer different format for the core protocol: atom based, rss based,json based, jsonc based.

In order to offer good parsing performance, we use the json based response as a default to get() the feeds.

Unfortunately, if we can set to read the feeds in json,the write methods require atom based data.

The server also sends back an atom response too.

We have therefore a hugly mixed of atom/json logic for now.

but...

The JSON-C format which is now being incorporated in google data based services will offer the same level of interaction as the atom based protocol.

Meaning that getting,inserting shall all be in JSON-C.

To avoid a dependency to an XML package (shall be deprecated soon) and keep the process reasonably fast

the packages handle all writing/updating methods and response from the servers with raw XML data.

This will change once JSON-C implementation is available in the most asked services.

METHODS

new

Accept a hash that specify the auth object handling acess to protected contents.

Example:

    use WebService::GData::Base;
        
    my $base   = new WebService::GData::Base(auth=>$auth);

auth

set/get an auth object that handles acess to protected contents.

The auth object will be used by post/insert/update/delete methods by calling two methods:

- set_authorization_headers

headers required by the authentication protocol

- set_service_headers

extra headers required by a particular service.

ie: WebService::GData::ClientLogin only implements the set_authorization_headers (set_service_headers being a stub doing nothing).

But the WebService::GData::YouTube::ClientLogin extends and implement the set_service_headers to add the developer key header.

These methods will receive the object calling them and the request object.

They shall add any extra headers required to implement their own authentication protocol (ie,ClientLogin,OAuth,SubAuth).

If the object can not handle these methods it will not be set.

Example:

    use WebService::GData::Base;
        
        #should be in a eval {... }; block to catch an error...
        my $auth = new WebService::GData::ClientLogin(email=>...);

    my $base = new WebService::GData::Base(auth=>$auth);
        #or
    my $base   = new WebService::GData::Base(); 
           $base->auth($auth);

query

set/get a query object that handles the creation of the query string. Default : WebService::GData::Query.

The query object will be used to add extra query parameters when calling WebService::GData::Base::get.

The query object should only implement the following methods (do not need to inherit from WebService::GData::Query):

- get

gives access to a particular parameter

- to_query_string

creates the query string.

- get('v')>=2

Query objects should all have a parameter specifying a version number parameter 'v' set to at least 2.

The WebService::GData::Query returns by default '?alt=json&prettyprint=false&strict=true&v=2' when to_query_string is called.

when you call WebService::GData::Base::get(), you should only set an url with no query string:

Example:

    use WebService::GData::Base;
        
        #should be in a eval { ... }; block...
        my $auth   = new WebService::GData::ClientLogin(email=>...);

    my $base   = new WebService::GData::Base(auth=>$auth);

        $base->query->alt('json-c');
    
    $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');
        #is in fact calling:
        #http://gdata.youtube.com/feeds/api/standardfeeds/top_rated?alt=json-c&prettyprint=false&strict=true&v=2

        #or set a new query object:
        $base->query(new WebService::GData::YouTube::Query());

get (url:Scalar)

Get the contents of a feed in a any format. If the format is json or jsonc, it will send back a perl object.

Accept an url with no query string. Query string will be removed before sending the request.

If an auth object is specified, it will call the required methods to set the authentication headers.

It will also set the 'GData-Version' header by calling $this->query->get('v');

When you call WebService::GData::Base::get(), you should only set an url with no query string.

Throws (die) a WebService::GData::Error if it fails to reach the contents.

You should put the code in a eval { ... }; block to catch any error.

Example:

    use WebService::GData::Base;
        
    my $base   = new WebService::GData::Base();
    
    $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');
        #is in fact calling:
        #http://gdata.youtube.com/feeds/api/standardfeeds/top_rated?alt=json-c&prettyprint=true&strict=true&v=2

        #the query string will be erased...
    $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated?v=2');
        #is in fact calling:
        #http://gdata.youtube.com/feeds/api/standardfeeds/top_rated?alt=json-c&prettyprint=true&strict=true&v=2

post (url:Scalar,content:Scalar)

Post data to an url with application/x-www-form-urlencoded content type.

Accept an url and the content to post.

If an auth object is specified, it will call the required methods to set the authentication headers.

It will also set the 'GData-Version' header by calling $this->query->get('v');

Throws (die) a WebService::GData::Error if it fails to reach the contents.

You should put the code in a eval { ... }; block to catch any error.

Example:

    use WebService::GData::Base;
        
        #you must be authorized to do any write actions.
    my $base   = new WebService::GData::Base(auth=>...);
    
        #create a new entry with application/x-www-form-urlencoded content-type
        my $ret = $base->post($url,$content);

insert (url:Scalar,content:Scalar)

Insert data to an url with application/atom+xml; charset=UTF-8 content type (POST).

Accept an url and the content that will be decorated with the raw xml tags:

<?xml version="1.0" encoding="UTF-8"?><entry xmlns="http://www.w3.org/2005/Atom" $xmlns>$content</entry>

The $xmlns part is specified by using the add_namespace method.

All the write methods require the contents formated as an atom feed.

We therefore must specify the namespaces that the content is using.

This shall be deprecated when everything switch to JSON-C format.

If an auth object is specified, it will call the required methods to set the authentication headers.

It will also set the 'GData-Version' header by calling $this->query->get('v');

Throws (die) a WebService::GData::Error if it fails to reach the contents.

You should put the code in a eval { ... }; block to catch any error.

Example:

    use WebService::GData::Base;
        
        #you must be authorized to do any write actions.
    my $base   = new WebService::GData::Base(auth=>...);
    
        #create a new entry with application/atom+xml; charset=UTF-8 content-type
        my $ret = $base->insert($url,$content);

update (url:Scalar,content:Scalar)

Update data to an url with application/atom+xml; charset=UTF-8 content type (PUT).

Accept an url and the content, that will be decorated with the raw xml tags: