++ed by:
גאבור סבו - Gábor Szabó

NAME

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

SYNOPSIS

    use WebService::GData::Base;

    #read only
        
    my $base = new WebService::GData::Base();

    my $ret  = $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');
    my $feed = $ret->{feed};

    #give write access
        
    $base->auth($auth);

    #now you can
    #get hidden/private contents
        
    my $ret = $base->get('http://gdata.youtube.com/feeds/api/users/default/playlists');

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

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

    #the content type is application/atom+xml; charset=UTF-8
        
    my $ret = $base->insert($uri,$content,$callback);

    #the content type is application/atom+xml; charset=UTF-8
        
    my $ret = $base->update($uri,$content,$callback);

    #modify the query string query string: ?alt=jsonc&v=2&prettyprint=false&strict=true
        
    $base->query->alt('jsonc')->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=false&strict=true&safeSearch=none
        
    $base->query->safe_search('none');

DESCRIPTION

inherits from WebService::GData

This package allows you to manipulate the data stored on Google servers. It grants you access to the main read/write (get,post,insert,update,delete) methods available for the google data APIs by wrapping LWP methods. Some actions require to be authenticated (ClientLogin,OAuth,SubAuth). If an authentication object is set at construction time, it will be called to add any extra headers the authentication mechanism requires. This package should be inherited by services (youtube,analytics,calendar) to offer higher level of abstraction.

Every request (get,post,insert,update,delete) will throw 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 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.

CONSTRUCTOR

new

PROXY METHODS

Any call to a method that is not defined in this package will be dispatched to the LWP::UserAgent instance. In getter context, they send back the WebService::GData::Base instance.

Example:

    use WebService::GData::Base;

    my $base = new WebService::GData::Base();
    
    #LWP::UserAgent timeout is set to 15 
    #and will look after environment variables for proxy settings
       $base->timeout(15)->env_proxy; 
       

SETTER/GETTER METHODS

auth

    Set/get an auth object that handles access to protected contents. The auth object will be used by post/insert/update/delete methods by calling two methods:

    • set_authorization_headers(base:WebService::GData::Base,req:HTTP::Request)

      - Headers required by the authentication protocol.

    • set_service_headers(base:WebService::GData::Base,req:HTTP::Request)

      - Extra headers required by a particular service.

    • source()

      - The name of the application. Will be used for the user agent string.

    These methods will receive the instance calling them and the request instance. They shall add any extra headers required to implement their own authentication protocol (ie,ClientLogin,OAuth,SubAuth). If the object can not handle the above methods it will not be set.

    Parameters

    none - use as a getter
    auth:Object - use as a setter: a auth object defining the necessary methods.

    Returns

    auth:Object in a setter/getter context.

    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. 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('value-name') - Gives access to a parameter value

    • to_query_string() - return the query string.

    • get('v') - should return a version number >=WebService::GData::Constants::GDATA_MINIMUM_VERSION

    Parameters

    none - use as a getter
    query:Object - use as a setter: a query object defining the necessary methods.

    Returns

    query:Object in a setter/getter context.

    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::Constants qw(:all);
        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(JSONC);
        
        $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=jsonc&prettyprint=false&strict=true&v=2
    
        #or set a new query object:
        $base->query(new WebService::GData::YouTube::Query());

override_method

    Set/get the override method.

    Depending on your server configurations, you might not be able to set the method to PUT/DELETE/PATCH. This will forbid you to do any updates or deletes. In such a case, you should set override_method to TRUE so that it uses the POST method but override it by the proper value (ie,PUT/DELETE/PATCH) using X-HTTP-Method-Override.

    Parameters

    none - use as a getter
    true_or_false:Scalar - use as a setter: WebService::GData::Constants::TRUE or WebService::GData::Constants::FALSE (default)

    Returns

    void in a setter context.
    override_state:Scalar in a getter context, either WebService::GData::Constants::TRUE or WebService::GData::Constants::FALSE.

    Example:

        use WebService::GData::Constants qw(:all);
        use WebService::GData::Base;
            
            
        #using override_method makes sense only if you are logged in
        #and want to do some write methods.
    
        my $auth = new WebService::GData::ClientLogin(email=>...);
    
        my $base = new WebService::GData::Base(auth=>$auth);
    
        $base->override_method(TRUE);
            
        $base->update($url,$content);
               

enable_compression

    Set/get the compression mode.

    Depending on your perl configuration, you might be able to handle data compress using gzip. By setting this method to TRUE, the data coming from Google servers will be gzipped and unzipped for you as a convenience. It may offer a way to limit the number of bytes exchanged over the network but requires more calculation on your side. By default, compression mode is not enabled.

    Parameters

    none - use as a getter
    true_or_false:Scalar - use as a setter: WebService::GData::Constants::TRUE or WebService::GData::Constants::FALSE (default)

    Returns

    void in a setter context.
    compression_state:Scalar in a getter context, either WebService::GData::Constants::TRUE or WebService::GData::Constants::FALSE.

    Example:

        use WebService::GData::Constants qw(:all);
        use WebService::GData::Base;
            my $base = new WebService::GData::Base();
           $base->enable_compression(TRUE);
        
        my $ret = $base->get($url);#the data was gzipped and ungzipped if possible
           

get_uri

    Get the last queried uri.

    Parameters

    none - getter only

    Returns

    uri:Scalar in a getter context, either undef if no query has been made or the uri with no query string as a Scalar.

    Example:

        use WebService::GData::Base;
            
        my $base = new WebService::GData::Base();
    
        $base->get('http://www.example.com?v=2');
            
        $base->get_uri();#'http://www.example.com'
               

user_agent_name

    Set or get the user agent name set.

    Parameters

    none - getter
    name:Scalar - set the user agent name

    Returns

    user_agent_name:Scalar the full user agent name when used in a getter context

    Example:

        use WebService::GData::Base;
            
        my $base = new WebService::GData::Base();
    
        $base->get('http://www.example.com?v=2');
            
        $base->user_agent_name();#WebService::GData::Base/2
            
        $base->auth($auth);#where $auth->source eq 'MyApp-MyCompany-ID'
    
        $base->user_agent_name();#MyApp-MyCompany-ID WebService::GData::Base/2
        
        $base->user_agent_name("my app");#MyApp-MyCompany-ID my app WebService::GData::Base/2
               

READ METHODS

get

    Get the content of a feed in any format. If the format is json or jsonc, it will send back a perl object. 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'); You should put the code in a eval { ... }; block to catch any error.

    Parameters

    url:Scalar - an url to fetch that do not contain any query string.

    Query string will be removed before sending the request.

    Returns

    response:Object|Scalar - a perl object if it is a json or jsonc request else the raw content.

    Throws

    WebService::GData::Error if it fails to reach the contents.

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

WRITE METHODS

All the following methods will set the 'GData-Version' header by calling $this->query->get('v'); You should put the code in a eval { ... }; block to catch any error these methods may throw.

post

    Post data to an url with application/x-www-form-urlencoded content type. An auth object must be specified. it will call the required methods to set the authentication headers.

    Parameters

    url:Scalar - the url to query
    content:Scalar|Binary - the content to post

    Returns

    response:Scalar - the response to the query in case of success.

    Throws

    WebService::GData::Error if it fails to reach the contents.

    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

    Insert data to an url with application/atom+xml; charset=UTF-8 content type (POST). An auth object must be specified. it will call the required methods to set the authentication headers.

    Parameters

    url:Scalar - the url to query
    content:Scalar - the content to post

    Returns

    response:Scalar - the response to the query in case of success.

    Throws

    WebService::GData::Error if it fails to reach the contents.

    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

    Update data to an url with application/atom+xml; charset=UTF-8 content type (PUT). An auth object must be specified. it will call the required methods to set the authentication headers.

    Parameters

    url:Scalar - the url to query
    content:Scalar - the content to put.

    Returns

    response:Scalar - the response to the query in case of success.

    Throws

    WebService::GData::Error if it fails to reach the contents.

    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 = $base->upate($url,$content);
            

delete

    Delete data from an url with application/atom+xml; charset=UTF-8 content type (DELETE).

    Parameters

    url:Scalar - the url to query

    Returns

    response:Scalar - the response to the query in case of success.

    Throws

    WebService::GData::Error if it fails to reach the contents.

    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 = $base->delete($url);
            

HANDLING ERRORS

Google data APIs relies on querying remote urls on particular services.

Some of these services limits the number of request with quotas and may return an error code in such a case.

All queries that fail will throw (die) a WebService::GData::Error object.

You should enclose all code that requires connecting to a service within eval blocks in order to handle it.

Example:

    use WebService::GData::Base;
        
    my $base   = new WebService::GData::Base();
        
    #the server is dead or the url is not available anymore or you've reach your quota of the day.
    #boom the application dies and your program fails...
    $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');

    #with error handling...

    #enclose your code in a eval block...
    eval {
        $base->get('http://gdata.youtube.com/feeds/api/standardfeeds/top_rated');
    }; 

    #if something went wrong, you will get a WebService::GData::Error object back:
    if(my $error = $@){

        #do whatever you think is necessary to recover (or not)
        #print/log: $error->content,$error->code
    }   

DEPENDENCIES

JSON

LWP

BUGS AND LIMITATIONS

If you do me the favor to _use_ this module and find a bug, please email me i will try to do my best to fix it (patches welcome)!

AUTHOR

shiriru <shirirulestheworld[arobas]gmail.com>

LICENSE AND COPYRIGHT

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

1 POD Error

The following errors were encountered while parsing the POD:

Around line 425:

=back without =over




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