The Java Persistence API (JPA), part of the Java Enterprise Edition 5 (Java EE 5) EJB 3.0 specification, greatly simplifies Java persistence and provides an object-relational mapping approach that allows you to declaratively define how to map Java objects to relational database tables in a standard, portable way that works both inside a Java EE 5 application server and outside an EJB container in a Java Standard Edition (Java SE) 5 application.
TopLink JPA provides extensions to what is defined in the JPA specification. These extensions come in persistence unit properties, query hints, annotations, TopLink own XML metadata, and custom API. For more information on where and how you use the extensions to customize JPA behavior to meet your application requirements, see Oracle Fusion Middleware Developer's Guide for Oracle TopLink .
For documentation on TopLink Essentials, refer to