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 3.1.x releases target JSR-338 Java Persistence 2.2.
They require Java8 and support the java.time API natively amongst other nice features.
Apache OpenJPA-3.1.x is fully backward compatible to our JPA-2.0 and JPA-1.0 releases.
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.
The 1.x releases
(1.2.2 is the latest) are a production ready, feature-rich, compliant
implementation of the Java Persistence API (JPA) 1.0 part of the JSR-220 Enterprise Java Beans 3.0
specification, which pass the Sun JPA 1.0b Technology Compatibility Kit.