The Google Shopping Content Java SDK by Google aims to simplify API calls. An example shows hot to interact with Google Calendar, which can be useful to work with the Google Shopping Content API. Authentication Auth 2.0 intends to reduce the amount of code needed. See documentation available at https://github.com/google/google-api-java-client#Documentation
Printful, a drop shipping service for custom print products and a product of the same team who created Startup Vitamins and BeHappy.me, has provided the Printful API that will allow people to easily integrate the functionality with their websites and applications. The service is specifically aimed at small and medium websites that want to offer print products, but don't want to handle the fulfillment and shipping of those products.