Hybernate

Hibernate is a powerful, high performance object/relational persistence and query service. Hibernate lets you develop persistent classes following object-oriented idiom - including association, inheritance, polymorphism, composition, and collections. Hibernate allows you to express queries in its own portable SQL extension (HQL), as well as in native SQL, or with an object-oriented Criteria and Example API.

Unlike many other persistence solutions, Hibernate does not hide the power of SQL from you and guarantees that your investment in relational technology and knowledge is as valid as always. The LGPL open source license allows the use of Hibernate and NHibernate in open source and commercial projects.
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Hibernate: Return on Investment (ROI) --September 19th, 2006 http://www.jacoozi.com/blog/?p=16
Performance
Hibernate supports various caching managers. It is a fast performer, has a dual-layer cache architecture, and may be used in a cluster. It’s pure Java design also allows it to be used in any J2EE application server




This tutorial provide step by step instructions on using Hibernate 3.0. Hibernate is popular open source object relational mapping tool for Java platform. It provides powerful, ultra-high performance object/relational persistence and query service for Java. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework. The Hibernate Query Language, designed as a "minimal" object-oriented extension to SQL, provides an elegant bridge between the object and relational worlds. Hibernate also allows you to express queries using native SQL or Java-based Criteria and Example queries. Hibernate is now the most popular object/relational mapping solution for Java

http://www.hibernate.org/hib_docs/reference/en/html/tutorial.html
http://www.roseindia.net/hibernate/index.shtml