There are client libraries available to help you write GData client applications in a variety of languages.
For each language, the client library provides tools and an abstraction layer, letting you easily construct queries and use response data without having to create HTTP requests or process HTTP responses by hand. Each client library provides classes that correspond to the elements and data types used by the Google data APIs. Each client library also provides extensions for specific Google services that have data APIs.
Java Developer Guides exist for specific Data APIs. They can be found under the page for each Data API, as linked on the left.
.NET Developer Guides exist for specific Data APIs. They can be found under the page for each Data API, as linked on the left.
The PHP client library is provided by Zend, as part of the Zend Framework. It is also available as a stand-alone release.
PHP Developer Guides exist for specific Data APIs. They can be found under the page for each Data API, as linked on the left.
Python Developer Guides exist for specific Data APIs. They can be found under the page for each Data API, as linked on the left.
The JavaScript client library is currently available only for use with Google Calendar and Blogger.
To use other Google data APIs with JavaScript, you can request JSON-format feeds instead of XML. For more information, see Using JSON with Google Data APIs. For working sample code, see the samples page.