Apache OpenJPA is a Java persistence project at The Apache Software Foundation
that can be used as a stand-alone POJO
persistence layer or integrated
into any Java EE compliant container and many other lightweight
frameworks, such as Tomcat and Spring.
The 2.x releases
(2.4.3 is the latest) are a production ready, compliant implementation of
the JSR-317 Java Persistence 2.0
specification, which is backwards compatible to the JPA 1.0 specification
and passes the Sun JPA 2.0 Technology Compatibility Kit.