simpleyql is a Java library that allows easy access to YQL-based Yahoo! APIs that need oAuth authorization.
It manages the process of exchanging/refreshing tokens and authorizing users - all your application needs to do is to store a single piece of information (authdata) for each authorized user, updating it on the database when it changes.
Based on the oauth.net reference Java libraries (oauth.googlecode.com), the library is licensed under the same Apache License V2.0.
More information:
Wiki: Credits
Wiki: Installation
Wiki: Rationale_and_Motivation
Wiki: Usage