Which is the most Complete, Stable, Reliable JPA 2.0 implementation?

[Anirudh Gupta]

Which is the most Complete, Stable, Reliable JPA 2.0(JSR-317) implementation(Open Source and Public Licence) available, EXCEPT HIBERNATE?

As of now the motivation to import such an implementation is mostly academic, however going forward I would prefer using the same implementation for project work.
Also I'd like to know, how complete is Hibernate's implementation of JPA 2.0(JSR-317)?
What are the salient differences between the 2?
Some official documentation reference(especially for the differences) would be much appreciated.

Thanks.

Anirudh.

[James Sutherland]

That is a tough question for anyone to answer impartially.

EclipseLink is the JPA 2.0 reference implementation, is the JPA implementation for Oracle WebLogic and Glassfish, and seems to have the largest user base next to Hibernate.

EclipseLink implements all of JPA 2.0, and also has a lot of extended functionality including:
- Caching, clustered cache coordination, cache invalidation, non-Id cache indexes, in-memory querying, database event driven invalidation
- MySQL, PostgreSQL, Derby, DB2, Sybase, SQL Server, H2, HSQL, Firebird, MaxDB, Symfoware
- NoSQL, MongoDB, Oracle NoSQL, XML files
- Oracle XDB, spatial, timestamp, QCN/DCN, flashback, VPD, AQ
- Data partitioning, multi-database sharding
- Composite persistence units, multi-database integration
- Multi-tenancy
- History, object versioning, historical querying
- Stored procedures, PL/SQL
- Dynamic models, extensions, external meta-data
- Performance, caching, query caching, batch fetching, join fetching, batch writing, fetch groups
- Connection pooling
- Object-relational Struct and Array data-types

See,
http://en.wikibooks.org/wiki/Java_Persistence/Persistence_Products